Dip Structure Research Articles

Linear and nonlinear ion-acoustic waves in nonrelativistic quantum plasmas with arbitrary degeneracy.

Linear and nonlinear ion-acoustic waves are studied in a fluid model for nonrelativistic, unmagnetized quantum plasma with electrons with an arbitrary degeneracy degree. The equation of state for electrons follows from a local Fermi-Dirac distribution function and applies equally well both to fully degenerate and classical, nondegenerate limits. Ions are assumed to be cold. Quantum diffraction effects through the Bohm potential are also taken into account. A general coupling parameter valid for dilute and dense plasmas is proposed. The linear dispersion relation of the ion-acoustic waves is obtained and the ion-acoustic speed is discussed for the limiting cases of extremely dense or dilute systems. In the long-wavelength limit, the results agree with quantum kinetic theory. Using the reductive perturbation method, the appropriate Korteweg-de Vries equation for weakly nonlinear solutions is obtained and the corresponding soliton propagation is analyzed. It is found that soliton hump and dip structures are formed depending on the value of the quantum parameter for the degenerate electrons, which affect the phase velocities in the dispersive medium.

Imaging the magmatic system of Mono Basin, California, with magnetotellurics in three dimensions

AbstractA three‐dimensional (3‐D) electrical resistivity model of Mono Basin in eastern California, unveils a complex subsurface filled with zones of partial melt, fluid‐filled fracture networks, cold plutons, and regional faults. In 2013, 62 broadband magnetotelluric stations were collected in an array around southeastern Mono Basin from which a 3‐D electrical resistivity model was created with a resolvable depth of 35 km. Multiple robust electrical resistivity features were found that correlate with existing geophysical observations. The most robust features are two 300 ± 50 km3 near‐vertical conductive bodies (3–10 Ω m) that underlie the southeast and northeastern margin of Mono Craters below 10 km depth. These features are interpreted as magmatic crystal‐melt mush zones of 15 ± 5% interstitial melt surrounded by hydrothermal fluids and are likely sources for Holocene eruptions. Two conductive east dipping structures appear to connect each magma source region to the surface. A conductive arc‐like structure (< 0.9 Ω m) links the northernmost mush column at 10 km depth to just below vents near Panum Crater, where the high conductivity suggests the presence of hydrothermal fluids. The connection from the southernmost mush column at 10 km depth to below South Coulée is less obvious with higher resistivity (200 Ω m) suggestive of a cooled connection. A third, less constrained conductive feature (4–10 Ω m) 15 km deep, extending to 35 km is located west of Mono Craters near the eastern front of the Sierra Nevada escarpment and is coincident with a zone of sporadic, long‐period earthquakes that are characteristic of a fluid‐filled (magmatic or metamorphic) fracture network. A resistive feature (103–105 Ω m) located under Aeolian Buttes contains a deep root down to 25 km. The eastern edge of this resistor appears to structurally control the arcuate shape of Mono Craters. These observations have been combined to form a new conceptual model of the magmatic system beneath Mono Craters to a depth of 30 km.

Dynamical Fano-Like Interference between Rabi Oscillations and Coherent Phonons in a Semiconductor Microcavity System.

We report on dynamical interference between short-lived Rabi oscillations and long-lived coherent phonons in CuCl semiconductor microcavities resulting from the coupling between the two oscillations. The Fourier-transformed spectra of the time-domain signals obtained from semiconductor microcavities by using a pump-probe technique show that the intensity of the coherent longitudinal optical phonon of CuCl is enhanced by increasing that of the Rabi oscillation, which indicates that the coherent phonon is driven by the Rabi oscillation through the Fröhlich interaction. Moreover, as the Rabi oscillation frequency decreases upon crossing the phonon frequency, the spectral profile of the coherent phonon changes from a peak to a dip with an asymmetric structure. The continuous wavelet transformation reveals that these peak and dip structures originate from constructive and destructive interference between Rabi oscillations and coherent phonons, respectively. We demonstrate that the asymmetric spectral structures in relation to the frequency detuning are well reproduced by using a classical coupled oscillator model on the basis of dynamical Fano-like interference.

The Geology of Canaan Valley

Abstract Canaan Valley (hereafter, the Valley) is located in the Folded Plateau Physiographic Province of the Appalachian Mountains. The Province features broad, gentle folds and low, structural dips. The Valley lies over the Blackwater Anticline, one of three structures that characterize the high plateau in which the Valley is set. The Anticline plunges northward, creating a broad amphitheater at the Valley's northern end. Southward, the Anticline truncates against a zone of discordance. The cause of the discordance is unknown. South of this zone, the Plateau is more deeply dissected, and the Anticline cannot be traced. In its place, there are three structures that terminate northward against the zone. Local stratigraphy controls the Valley's landscape. Six stratigraphic units—the Pennsylvanian Kanawha Formation, New River Formation, Mississippian Mauch Chunk Formation, Greenbrier Limestone Formation, Price Formation, and Devonian Hampshire Formation—outcrop in the Valley. The ridges in the Valley are su...

Highly ionized xenon and volumetric weighting in restricted focal geometries

The ionization of xenon atoms subjected to 42 fs, 800 nm pulses of radiation from a Ti:Sapphire laser was investigated. In our experiments, a maximum laser intensity of ∼2×1015W/cm2 was used. Xenon ions were measured using a time-of-flight ion mass spectrometer having an entrance slit with dimensions of 12μm×400μm. The observed yields Xen+(n=1−7) were partially free of spatial averaging. The ion yields showed sequential and nonsequential multiple ionization and dip structures following saturation. To investigate the dip structures and to perform a comparison between experimental and simulated data, with the goal of clarifying the effects of residual spatial averaging, we derived a hybrid analytical-numerical solution for the integration kernel in restricted focal geometries. We simulated xenon ionization using Ammosov-Delone-Krainov and Perelomov-Popov-Terent'ev theories and obtained agreement with the results of observations. Since a large number of experiments suffer from spatial averaging, the results presented are important to correctly interpret experimental data by taking into account spatial averaging.

Transport properties for a quantum dot coupled to normal leads with a pseudogap

We study transport properties for a quantum dot coupled to normal leads with a pseudogap density of states at zero temperature, using the second-order perturbation theory based on the Keldysh formalism. We clarify that the hybridization function $\Gamma(\omega)\propto |\omega|^r\; (0 \le r < 1) $ induces the cusp or dip structure in the density of states in the dot when finite bias voltage is applied to the interacting quantum dot system. It is found that the current-voltage characteristics and differential conductance are drastically changed at $r=1/2$.

Vertical seismic profile Kirchhoff migration with structure dip constraint

Prestack Kirchhoff depth migration is commonly used in borehole seismic imaging, where there is uneven illumination due to the limitations of the source-receiver geometry. A new vertical seismic profile (VSP) migration/imaging workflow has been established that incorporates the structure-dip information derived from a newly developed structure tensor analysis into the existing VSP Kirchhoff migration/imaging technique. This allows us to better image the structures in the vicinity of a borehole and the far-field dipping events away from the borehole. We tested the workflow with the HESS salt model. The results were compared with those from reverse time migration, which found that Kirchhoff migration combined with structure-dip information not only reduced ambiguities of the imaging result but also allowed for imaging dip structures (e.g., fault) in the far region from the borehole. This allows for imaging dip structures and provides a useful extension of existing VSP imaging capabilities using Kirchhoff migration.

Basin and petroleum system modeling of the Cretaceous and Jurassic source rocks of the gas and oil reservoirs in Darquain field, south west Iran

In south west Iran, in the Abadan Plain, there are several giant gas and oil reserves in Jurassic and Cretaceous carbonates, such as Darquain, where there are excellent source rocks in the Early Cretaceous and Jurassic successions. In present study, petroleum generation and migration from these source rocks were evaluated. Maturity state of organic matter was determined with Organic petrography and results were used for calibration of thermal model. Basin modeling was used for investigation of petroleum generation and migration history. Burial history and 3D thermal model were constructed for the study area using Temis suite and Genex software. Modeling shows source rocks of Jurassic, such as Sargelu and Neyriz are in gas maturity state, oil generation phase passed before Cenozoic. It appears that gas from Jurassic source rocks accumulated in Najmeh and did not reach to Cretaceous Fahliyan reservoir. Cretaceous reservoir in Fahliyan Formation has been charged by the Garau Formation. This source rock reached to oil window in Early Cretaceous time and began hydrocarbon expulsion at the end of Cretaceous when the Darquain structure formed. Migration paths of hydrocarbons shifted from NE to SW direction about 11 Ma in response to changes in regional structural dip contemporary with the Zagros Orogeny. Modeling results indicate that the quantity of gas and oil generated in the kitchen area was more than the reservoirs' capacity. Therefore, the surplus hydrocarbon could have migrated laterally out of reservoir area.

Magnetized sheath near positively biased wall between two permanent magnetic plates

The characteristics of magnetized electron sheath near a positively biased conducting wall parallel to magnetic field formed between two permanent magnetic plates were experimentally investigated in a double plasma device. The magnetic field strength between the magnetic plates is about 1200 G which is sufficient to magnetize the plasma such that the ion gyroradius is comparable to the electron Debye length. A virtual cathode (or potential dip) structure was found between the electron-rich sheath and bulk plasma. For a given neutral gas pressure, the potential minimum (dip position) remains almost the same for different positive biases on the wall. For a given bias on the wall, however, the electron sheath thickness and the potential drop from the bulk plasma to the dip decrease with the increase of the neutral gas pressure. In addition, the electron sheath and potential dip appear to be wider and deeper in the downstream side of the wall.

Magnetic Field of BG-VG Transition Depending on the Nanorods Shape in &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\hbox{BaHfO}_{3}$&lt;/tex-math&gt;&lt;/inline-formula&gt;-Doped &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\hbox{SmBa}_{2}\hbox{Cu}_{3}\hbox{O}_{y}$&lt;/tex-math&gt;&lt;/inline-formula&gt; Films

The vortex state under the magnetic held around vortex glass (VG)-Bose glass (BG) transition held was investigated in the SmBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (SmBCO) films with BaHfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BHO) nanorods. We prepared two films with different forms of the nanorods (thick-straight and thin-tilted), and we used the magnetic held angular dependence of flux flow resistivity (p - θ) to identify a vortex state. From a comparison between the p - θ curves in completely BG and VG phases, it was revealed that the existence of deep and sharp dip structure along the c-axis direction of the SmBCO matrix (B//c) was an evidence of the BG state in both the films. In the magnetic held region around VG-BG transition, shallower and broader dips than the dips in the BG state were observed at B//c in both the films. In addition, the dips became deeper with increase of the magnetic held in this region in each film. Therefore, we considered the vortex state of both the films was an intermediate and/or a transient state of BG and VG. Under all magnetic fields, the film with thick and straight BHO nanorods showed stronger c-axis correlated flux pinning force than the film with thin and tilted nanorods. We suggested the intermediate state of the hlm with thicker and straighter nanorods was similar to the BG state compared with another hlm from the both of experimental results and reported theory.

MeshIt—a software for three dimensional volumetric meshing of complex faulted reservoirs

Flow, mass and energy transport processes in natural reservoirs are controlled to a large degree by the presence of geological heterogeneities including structures such as fractures and fault zones embedded in a spatially varying three-dimensional (3D) porous matrix of the reservoir. Despite recent advances, currently, state-of-the-art models rely on a number of simplifications partly related to our inability to represent heterogeneities as observed in the field into dynamic model realizations. In this respect, an adequate geometric representation of the discrete system is a basic requirement. In this study, we show how fundamental concept from computational geometry can be assembled and used to bridge the gap between geological and dynamic forward models. The result is an automated, open source software solution (MeshIt) to generate quality 3D meshes suitable for the study of flow and transport processes in faulted and fractured reservoirs. The software enables us to integrate into a 3D volumetric representation dipping structures, comprising fault zones and fractures as well as inclined well paths. This permits us to correctly simulate interactions between discrete flow paths along these interacting components and the 3D flow within the reservoir matrix. The crucial factor that makes the approach applicable to real case reservoirs is that all algorithms are local and scalable parallel and have computing times increasing approximately linearly with data volumes. We test the performance and the robustness of the software against three different scenarios of increasing complexity and further discuss current limitations and range of applicability of the software. Although all examples describe geothermal applications, it is worth mentioning that the approach is equally valid for other applications in geoscience from oil and gas industry to carbon capture and sequestration issues.

Critical velocity for vortex shedding in a Bose-Einstein condensate

We present measurements of the critical velocity for vortex shedding in a highly oblate Bose-Einstein condensate with a moving repulsive Gaussian laser beam. As a function of the barrier height $V_0$, the critical velocity $v_c$ shows a dip structure having a minimum at $V_0 \approx \mu $, where $\mu$ is the chemical potential of the condensate. At fixed $V_0\approx 7\mu$, we observe that the ratio of $v_c$ to the speed of sound $c_s$ monotonically increases for decreasing $\sigma/\xi$, where $\sigma$ is the beam width and $\xi$ is the condensate healing length. The measured upper bound for $v_c/c_s$ is about 0.4, which is in good agreement with theoretical predictions for a two-dimensional superflow past a circular cylinder. We explain our results with the density reduction effect of the soft boundary of the Gaussian obstacle, based on the local Landau criterion for superfluidity.

Finger-gate manipulated quantum transport in Dirac materials

We investigate the quantum transport properties of multichannel nanoribbons made of materials described by the Dirac equation, under an in-plane magnetic field. In the low energy regime, positive and negative finger-gate potentials allow the electrons to make intra-subband transitions via hole-like or electron-like quasibound states (QBS), respectively, resulting in dips in the conductance. In the high energy regime, double dip structures in the conductance are found, attributed to spin-flip or spin-nonflip inter-subband transitions through the QBSs. Inverting the finger-gate polarity offers the possibility to manipulate the spin polarized electronic transport to achieve a controlled spin-switch.

Mega‐scale Moho relief and the structure of the lithosphere on the eastern flank of the Viking Graben, offshore southwestern Norway

AbstractThe International Lithosphere Project deep reflection seismic survey in the Norwegian sector of the North Sea has been reprocessed, particularly focusing on the deep crust, the reflection Moho, and the upper mantle. The data display shifting reflection patterns of the crust and the upper mantle parallel to the eastern margin of the Viking Graben. In the upper crust, which is mainly seismically transparent by the processing techniques utilized here, large‐scale structural features like detachment shear zones and master faults can be identified. Several of the major onshore faults and shear zones match seismic features in the seismic lines. Many of these structures acted as extensional shear zones in the Devonian. The middle crust is of variable reflectivity, whereas the lower crust is generally strongly reflective and is particularly so in the southern domain. The reflection Moho is identified throughout the study area but is of variable character. The presence of a S(E) dipping structure (Hardanger Moho Offset) that displaces the Moho by approximately 10 km, extends deep into the mantle (below the 50 km line depth), is positioned where the shallower Hardangerfjord Shear Zone, which flattens on the level of the middle crust, is situated. The Hardangerfjord Shear Zone/Hardanger Moho Offset‐system coincides with change of the crustal thickness (depth to Moho), a change that also coincides with the transition from thin‐ to thick‐skinned Caledonian deformation. Intramantle reflections are common in the study area, some of which are interpreted as shear zones, whereas others most likely represent magmatic intrusions.

Bulk superconducting gap of V3Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V3Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (Tc=15.9K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V3Si is a single-gap s-wave superconductor.

Probing dynamic information and spatial structure of Rydberg wave packets by harmonic spectra in a few-cycle laser pulse

We demonstrate that the dynamic information and the spatial structure of a Rydberg wave packet formed by two neighboring Rydberg states can be simultaneously probed by harmonic spectra in a few-cycle laser pulse, where the Rydberg wave packet is produced by a pump laser field. By controlling the time delay of the pump-probe laser pulses, the harmonic spectra present a periodic variation, which directly illustrates the electron oscillation between the two neighboring Rydberg states. Specifically, by taking advantage of the periodic variation of the harmonic efficiency and the dip structure in the spectrum, one can detect the spatial characteristics and the dynamic information of the initial Rydberg wave packet.

Structure of a low-enthalpy geothermal system inferred from magnetotellurics — A case study from Sri Lanka

First comprehensive geothermal exploration in Sri Lanka was conducted in 2010 encompassing seven thermal springs, of which Kapurella records the highest temperature. The study consisted of passive magnetotelluric (MT) soundings, in which static shifts were corrected using time domain electromagnetic method (TDEM). A frequency range of 12,500–0.001Hz was used for MT acquisition and polar diagrams were employed for dimensionality determination. MT and TDEM data were jointly inverted and 2D models were created using both transverse electric and transverse magnetic modes. A conductive southeast dipping structure is revealed from both phase pseudosections and the preferred 2D inversion model. A conductive formation starting at a depth of 7.5km shows a direct link with the dipping structure. We suggest that these conductive structures are accounted for deep circulation and accumulation of groundwater. Our results show the geothermal reservoir of Kapurella system with a lateral extension of around 2.5km and a depth range of 3km. It is further found that the associated dolerite dike is not the source of heat although it could be acting as an impermeable barrier to form the reservoir. The results have indicated the location of the deep reservoir and the possible fluid path of the Kapurella system, which could be utilized to direct future geothermal studies. This pioneering study makes suggestions to improve future MT data acquisition and to use boreholes and other geophysical methods to improve the investigation of structures at depth.

Pitfalls and limitations in seismic attribute interpretation of tectonic features

Seismic attributes are routinely used to accelerate and quantify the interpretation of tectonic features in 3D seismic data. Coherence (or variance) cubes delineate the edges of megablocks and faulted strata, curvature delineates folds and flexures, while spectral components delineate lateral changes in thickness and lithology. Seismic attributes are at their best in extracting subtle and easy to overlook features on high-quality seismic data. However, seismic attributes can also exacerbate otherwise subtle effects such as acquisition footprint and velocity pull-up/push-down, as well as small processing and velocity errors in seismic imaging. As a result, the chance that an interpreter will suffer a pitfall is inversely proportional to his or her experience. Interpreters with a history of making conventional maps from vertical seismic sections will have previously encountered problems associated with acquisition, processing, and imaging. Because they know that attributes are a direct measure of the seismic amplitude data, they are not surprised that such attributes “accurately” represent these familiar errors. Less experienced interpreters may encounter these errors for the first time. Regardless of their level of experience, all interpreters are faced with increasingly larger seismic data volumes in which seismic attributes become valuable tools that aid in mapping and communicating geologic features of interest to their colleagues. In terms of attributes, structural pitfalls fall into two general categories: false structures due to seismic noise and processing errors including velocity pull-up/push-down due to lateral variations in the overburden and errors made in attribute computation by not accounting for structural dip. We evaluate these errors using 3D data volumes and find areas where present-day attributes do not provide the images we want.

Enhanced spin thermoelectric effects in BN-embedded zigzag graphene nanoribbons

Spin thermoelectric effects in BN-embedded zigzag graphene nanoribbons (ZGNRs) are studied by a first-principles method. The multiple spin-up (spin-down) quasi-bound states below (above) the Fermi level can be introduced by the BN bonded pairs, leading to the dip structures in the transmission spectra. We further find that the spin thermoelectric effect at the Fermi level is obviously stronger than the corresponding charge thermoelectric effect. As the more BN bonded pairs are gradually doped from the edge to middle regions, the spin thermoelectric figure of merit (FOM) can be improved up to ten times than the charge thermoelectric FOM. A pure spin current can also be achieved in the BN-embedded ZGNRs under an external thermal bias.

Hetero-pairing and pseudogap phenomena in an ultracold Fermi gas with mass imbalance

We investigate strong-coupling properties of a unitary Fermi gas consisting of two different species with different masses. Including pairing fluctuations within the self-consistent T-matrix approximation, we calculate the single-particle density of states in the normal state. We show that the pseudogap phenomenon, which is characterized by a dip structure in the density of states around ω = 0, appears more remarkably in the light mass component than in the heavy mass component. As a result, the pseudogap temperature, which is determined as the temperature at which the pseudogap disappears in the density of states, is higher in the former than in the latter. We also find that this different pseudogap temperatures lead to the existence of two kinds of pseudogap regions. That is, one is the ordinary pseudogap regime where the pseudogap appears in both the component, and the other case is that the light mass component only exhibits the pseudogap phenomenon. As the origin of these component- dependent pseudogap phenomena, we point out the importance of different Fermi temperatures between the two components. Since the formation of hetero-Cooper pairs and their condensation are expected in various systems, such as a 6Li-40K Fermi gas mixture, an exciton (polariton) gas, as well as color superconductivity, our results would be useful for the understanding of strong-coupling properties of these novel Fermi condensates.