Magnetic Zone Research Articles

Reconstruction of the subsurface crustal and radiogenic heat models of the Bornu Basin, Nigeria, from multi-geophysical datasets: Implications for hydrocarbon prospecting

This study aims to reconstruct the subsurface crustal and radiogenic heat models from integrated airborne magnetic and gamma-ray spectrometric and satellite gravity methods for implications on hydrocarbon exploration in the Bornu Basin, NE Nigeria. The results revealed the basin’s lithologies and shallow-to-deep structures (faults and lineaments) and their trends, depicting contrasting magnetic intensities, gravity anomalies, and radionuclide concentrations. High magnetic anomalous zones in the southern and southeastern parts of the basin could be associated with the influence of the intrusive body (porphyritic granite) of high magnetization as observed in the 2D magnetic/gravity models. Moderate to low anomalous zones suggested thick sedimentation in the northeastern and central areas. The total horizontal derivatives (THDR) and Rose diagrams of the magnetic and Bouguer anomalies revealed major lineaments/faults in the NE-SW, NNE-SSW, and E-W directions. These structures likely serve as the migratory pathways/traps for the hydrocarbons. The structures delineated on the radioelements ratio, and composite maps also correlate with those identified on the THDR maps, especially the major SE-NW structure created by magmatic intrusion in the southeastern part of the basin. The estimated total radiogenic heat production (RHP) rates for the study area decreased in the order of 740.46 > 674.16 > 665.35 > 462.23 > 415.17, with the maximum obtained from the Yolde Formation (YF) and Pindiga Formation (PF). These are attributable to clay, limestone, shale, and ferruginized sandstone. The Chad Formation (CF), on the other hand, had thicker sediment (6.8 km) and a maximum RHP of 550 ρWkg-1, which is relatively low (<750 ρWkg-1) for hydrocarbon maturation and accumulation. Hence, CF is not viable for hydrocarbon prospecting as the RHP obtained might not be sufficient. The RHP > 797.87 ρWkg-1 obtained in the PF and the YF falls within the moderate RHP windows (750–1500 ρWkg-1) for sufficient hydrocarbon maturation and accumulation in the Bornu Basin.

Этос креативного пространства в современном городе

The rapid development of creative industries changes key principles of urban development. This paper reveals ethical and aesthetic values that determine a specific character of creative space in contemporary cities. The author considers those conditions under which a new ethics emerges in this space and explicates its specific features. The article suggests the hypothesis that it is possible to compare the formation logics of the rococo salon community in opposition to the classicist and baroque aesthetics of the absolutist regime and the present-day creative class in its opposition to the etiquette of the dominant ideology. This analogy allows considering creative space as a superhistorical model for the aestheticization of political resistance, its further institutionalization, and transfiguration. Special attention is paid to the analysis of the value of novelty in different sociocultural and historical contexts of its embodiment and correspondent judgment strategies. The final part of the article outlines “the space of passion” as an essential expression and symbolic characteristic of magnetic urban zones.

APPLICATION OF GROUND MAGNETIC METHOD FOR DELINEATION SUBSURFACE STRUCTURAL CONTROL ON SULPHIDE ORE DEPOSIT IN BENUE TROUGH; A CASE STUDY OF IKENYI IZZI

The sulphide ore mineralization occurrence in the area is structurally controlled. However, wrong structural delineation has led to some recorded mine failures and revenue loss faced by investors and government. Therefore, subsurface structural mapping is crucial for the successful and reliable delineation of sulphide ore enrichment zone within the area. To this effect ground magnetic method was used to appraise the structural elements associated with the sulphide mineralization in Ikenyi Izzi area, part of Southern Benue Trough. The total magnetic field intensity (TMI) was recorded, corrected, and separated into regional and residual magnetic fields. The TMI varies from 33259.7–33329.7nT with an average field value of 33299.4nT. Whereas residual susceptibility value ranges from -36.3–25.7nT with significant magnetic closures which correspond to the areas of low and high susceptibility values. Three dominant structural geometries was identified in the area; NE-SW&gt;NW-SE&gt;N-S with few E-W structures. The NE-SW and some N-S structures characterized areas of high magnetic anomaly closures and are associated with the regional trends of the igneous intrusive rocks, whereas NW-SE structures host the ore deposit (Trending ≥N300°) and dominantly associated with areas of low magnetic anomaly zones. The cross-cutting relationship of the NE-SW, N-S and NW-SE structures infers a close association of the intrusions and mineralization, which was validated by ground truthing. The residual susceptibility values of 1 to 10nT and ≥ 10nT were inferred as shale and intrusive rocks respectively. The implication of this study denotes that missing appropriate structural elements delineation could lead to abortive mines target.

Ion-acoustic wave dynamics and sensitivity study in a magnetized Auroral phase plasma

The dynamic behavior of ion-acoustic waves (IAWs) inside a magnetized auroral zone plasma including ions as well as two-temperature electrons is investigated. The Kadomtsev–Petviashvili (KP) and modified KP (mKP) equations are provided using the reductive perturbation method (RPT). In fluid dynamics, plasma physics, and electrodynamics, mKP equation can be utilized to characterize wave phenomena. It increases our interest due to its significant physical and mechanical value. The new extended direct algebraic approach is used to compute several traveling wave patterns for the nonlinear mKP equation. It is a simple, concise and general method in symbolic computations for solitary wave solutions for nonlinear problems. It yields dark solitary solutions, the community for semi-dark soliton results, dark singular soliton effects, kink soliton results, and soliton consequences encompassing trigonometric function, mixture hyperbolic function, as well as rational functions. Some arbitrarily chosen solutions are displayed visually for physical understanding. Moreover, the sensitivity of the perturbed dynamical structure equivalent to the mKP equation has been explored. Furthermore, the effect of IAWs spectral index on the parameters of the solitary-wave solutions and the sensitivity of the perturbed dynamical system of mKP equations is investigated in detail.

Influence of the oceanic crust structure on marine magnetic anomalies: Review and forward modelling

Marine magnetic anomaly strips are important for plate tectonic studies, thereby promoting the development of the geoscience revolution. Most previous studies typically consider a lava layer with vertical polarity boundaries as a simplified magnetic source layer. However, it cannot accurately explain the observed magnetic anomaly data; thus, complex oceanic crusts with multiple magnetic source layers, such as lava, dike, and gabbro layers, and various polarity boundary dip angles should be considered. To date, there is a lack of systematic understanding about how the dike and gabbro layers affect the total marine magnetic anomalies, particularly the effect of lava layers with different boundary inclinations on the intensity and polarity boundary of the magnetic anomaly. This study aimed to confirm the significance of these factors. Hence, we systematically simulated and analysed the magnetic anomaly characteristics with different inclination and magnetization settings for each layer using the forward modelling method and determined the impact of the complexity of the magnetic structure of the oceanic crust on the magnetic anomaly. Our results showed that the contributions of the dike and gabbro layers to the magnetic anomalies was up to 10%–30% and cannot be ignored. Moreover, the polarity transition point may shift with the inclination of the lava, dike, and gabbro layers but is insensitive to the magnetization of each layer. This study emphasizes the significance of the dike and gabbro layers and the inclination variations of different layers, which should be thoroughly studied. This study facilitates a reasonable interpretation of the magnetic structure of the oceanic crust and further refines the boundary of the magnetization zone with alternative polarity.

Geophysical and morphological constraints on active tectonics in the Eastern Pontides (Turkey)

The Eastern Pontides in northern Anatolia (Turkey) offers an exceptional record of significant tectonic evolution from subduction to crustal thickening and Anatolian escape tectonics. Here, we provide ground magnetic measurements at 435 points integrated with aeromagnetic data, remote sensing, and surface geological features from the literature reveal all these tectonic deformation effects on the Eastern Pontides. The region, which is tectonically separated into three sub-zones, clearly revealed from both aero and ground magnetic data. Lineament analysis was carried out to reveal the deformation styles of the region and to compare different data sets. According to the lineament analyzes obtained from the aero&ground magnetic data and all the other data sets, similar results were obtained for the three sub-zones. Although slight differences were obtained results between the used methods and zones, the main lineament orientation is calculated in the E-W direction. Thus, the obtained results emphasize that tectonic deformation effects resulting from long-term ∼N-S convergence and crustal shortening (subduction, collision, obduction) may still dominate the region. In addition to the lineament results, high (low) magnetic zones in the E-W orientation are also evident. Considering the resolution of the data used, these magnetic changes can be associated with large scale geological structures rather than surface lithological changes. Despite the existence of an active dextral the North Anatolian Fault Zone, the zone is not evident from the magnetic results so the transcurrent tectonic regime probably still not dominant in the entire region.

Second-order phase transition of silicon from a band insulator to metal induced by strong magnetic fields

We present the second-order phase transition from a band insulator to metal that is induced by a strong magnetic field. The magnetic-field dependences of the magnetization and energy band gap of a crystalline silicon immersed in a magnetic field are investigated by means of the nonperturbative magnetic-field-containing relativistic tight-binding approximation method (2018 Phys. Rev. B 97 195135). It is shown that the energy band gap disappears at the critical magnetic field of 2.22 × 104 (T). At the critical magnetic field, the magnetic-field dependence of the magnetization exhibits a kink behavior, which means that this phenomenon is the second-order phase transition from a band insulator to metal. It is found that in strong magnetic fields above the critical magnetic field, namely in the metallic phase, the oscillation of the magnetization appears. It is shown that this magnetic oscillation comes from the magnetic energy bands in the magnetic Brillouin zone that change from the occupied states to unoccupied states or vice vasa.

Aeromagnetic and Radiometric Data Interpretation to Delineate the Structural Elements and Probable Precambrian Mineralization Zones: a Case Study, Egypt

This study focused on joint interpretation of the aeromagnetic and radiometric data to allocate and describe the structural elements and mineralization zones such as uranium, gold, and sulfide in the Gebel Umm Tineidba and its surroundings, Eastern Desert, Egypt. The study region is covered by exposures of Precambrian rocks such as gneisses, migmatites, ophiolitic mélange, metavolcanics, younger granites, and Quaternary sedimentary covers. The application of the total intensity magnetic and reduced-to-pole maps, power spectrum, analytic signal, tilt-angle, and local wavenumber maps helps in recognizing magnetic sources distribution, lineament features, and mineral zones delineation. The obtained results indicate that the depths of the deeper NE–SW, NNE–SSW, and N–S trending structures extend from 400 to 1750 m and shallower ones range from 100 to 400 m. Finally, the main trends of these structures affect the probable mineralization zones.

Metallic-Mineral Prospecting Using Integrated Geophysical and Geochemical Techniques: A Case Study from the Bela Ophiolitic Complex, Baluchistan, Pakistan

An integrated geophysical and geochemical investigation was conducted to investigate the metallic minerals hosted in the mafic and ultramafic rocks in the Bela Ophiolitic Complex. Two thousand magnetic observations were made along with six vertical electrical soundings, with Induced Polarization (IP) targeting the anomalous magnetic zones. The magnetic raw field data were interpreted qualitatively and quantitatively, and two anomalous zones (A1 and A2) were identified on the magnetic maps. The residual magnetic values in the high-magnetic-anomalous zone (A2) ranged from 310 nT to 550 nT, while the magnetic signatures in the low-magnetic zone (A1) ranged from –190 nT to 50 nT. The high-anomalous zone (A2) was distinguished by a high IP value ranging from 3.5 mV/V to 15.1 mV/V and a low apparent and true resistivity signature of 50 ohm·m. Whereas, the low-anomalous zone (A1) was distinguished by very low IP values ranging from 0.78 mV/V to 4.1 mV/V and a very high apparent and true resistivity of 100 ohm·m. The Euler deconvolution was used to determine the depth of the promising zone, which for A1 and A2 was in the 100 m range. The statistical analysis was carried out using hierarchical classification to distinguish between background and anomalous data. The high-magnetic anomalous signature of probable mineralization was in the range of 46,181 nT–46,628 nT, with a total intensity range of 783 nT–1166 nT. The major and trace-element analysis of the 22 rock and stream sediments collected from the high-magnetic-anomalous zone confirmed the mineralization type. The geomagnetic and geophysical cross sections revealed that anomalous mineralization was concentrated with the anticlinal Bela Ophiolitic Complex. The generated results also aided in the identification of rock boundaries, depth, and hidden faults in the area. The findings revealed that the study area has excellent mineralization associated with the ultramafic-rock sequence.

Investigation of magnetorheological grease flow under the influence of a magnetic field

In this work, we present a novel magnetohydrodynamic flow study using micro-Particle Image Velocimetry (m-PIV) in a rectangular channel under the effect of a uniform transverse magnetic field. This study is the first of its kind to explore the use of magnetorheological grease in machine components such as bearings. Rheological characterisation of grease samples establishes the non-linear relationship between the shear rate and shear stress and thus confirms the non-Newtonian behaviour of the grease. The flow follows a parabolic path away from the magnetic field. Experimental studies reveal that the flow velocities reduce considerably from 11.9 m/s to 1.7 m/s in the vicinity of the magnetic zone due to the formation of strong field-induced chains. These chains are responsible for an increase in localized yield stress of grease thereby causing a surge in the resistance to flow. Further, numerical and analytical models are developed to predict the velocity field under a magnetic field. The analytical model can accurately predict the flow velocity for different magnetic field strengths. It can be deduced that the obtained correlation is a suitable model for estimating the velocity values at different magnetic field strengths for flow in similar configurations. Numerical results predicted by a finite volume method-based solver are in good agreement with the experiments on the upstream side. Flow velocities increase with flow rate and decrease with the onset of the magnetic field. Pressure drop along the channel length shows an abrupt change in the magnetic zone. This is because of the disturbance of the normal flow regime due to the presence of the magnetic field. The grease flow disturbs the distribution of magnetic field lines resulting in flow-induced field strength of B = 0.1 T against an applied external magnetic field strength value of B = 0.3 T. The present study analyses the effects of an external field on the flow patterns of magnetorheological grease. It confirms that magnetorheological grease provides controllability in applications, because flow properties can be varied by tuning the magnetic field strength.

Geophysics and origin of the Deniliquin multiple-ring feature, Southeast Australia

Major geophysical elements of the Deniliquin multiple-ring feature, a spatially distinct buried structure in mainland southeast Australia, suggest it represents the deep-seated root zone of a large impact structure from which the upper levels, including the original crater, central uplift and associated breccia, have been eroded. Principal features include (A) a multiple ring total magnetic intensity (TMI) pattern; (B) a central quiet magnetic zone; (C) circular Bouguer gravity patterns; (D) an underlying mantle Moho rise about 10 km shallower than under the adjacent Tasman Orogenic Belt; (E) radial faults associated with magnetic and demagnetized anomalies. The minimum radius of the TMI ring is ~260 km, including a central circular quiet magnetic zone about ~120 km in radius. In the east the feature is faulted against the Early Paleozoic Lachlan Orogenic belt whereas in the west it deflects the northwest and northeast trending Early Cambrian ~525–514 Ma Kanmantoo Group. An interpretation of the Deniliquin multiple-ring feature in terms of an orocline is inconsistent with the discontinuity between the feature and surrounding regional structural trends. Limits on the age of the Deniliquin feature are defined by the onset of the Adelaide fold belt at 514 +/− 5 Ma (Foden et al., 1999) and the ~427–417 Ma age of intrusive Silurian granites. Basement drill cores within the Deniliquin multiple-ring feature show Boehm lamellae but did not reveal shock metamorphic textures. Based on its multiple-ring structure, structural distinction from surrounding regional structural trends, occurrence of a central quiet magnetic zone, an underlying shallower Moho and radial faults associated with magnetic bodies, we suggest the Deniliquin multiple-ring feature may represent the deep seated root zone of a large impact structure.

RKKY-type in-plane ferromagnetism in layered Mn1/4NbS2 single crystals

Placing the layers of the $3d$ magnetic elements in the van der Waals gap pulls the Nb/Ta-based transition metal dichalcogenides family from a nonmagnetic to a magnetic zone. However, the magnetic spectrum is strongly sensitive to the specific combination of host lattice and type of intercalated magnetic element and thus each combination needs a proper explicit study. In this context, we systematically investigate the magnetization of the Mn-intercalated layered ferromagnet ${\mathrm{Mn}}_{1/4}{\mathrm{NbS}}_{2}$ single crystal. Magnetization measurement revealed paramagnetic to ferromagnetic phase transition at around 105 K and an easy in-plane ($H\ensuremath{\perp}c$) significantly high magnetic anisotropy. The in-plane magnetic anisotropic energy (MAE) evaluated via the noncollinear first-principle approach is $\ensuremath{\sim}\ensuremath{-}600 \ensuremath{\mu}\mathrm{eV}$ per unit cell. The position of the Fermi level in between the spin-up and spin-down Mn states suppresses the positive contribution in the overall MAE, which lifts the overall MAE negative (in plane) with a larger size in ${\mathrm{Mn}}_{1/4}{\mathrm{NbS}}_{2}$. The comprehensive analysis of magnetization isotherms measured in the vicinity of ${T}_{c}$ with magnetic field $H$ applied parallel to the $ab$ plane ($H\ensuremath{\perp}c$) yields the asymptotic critical exponents $\ensuremath{\beta}=0.3251(2)$ and $\ensuremath{\gamma}=1.2(1)$, and $\ensuremath{\delta}=4.691(1)$. These critical exponents fulfill the scaling relation and scaling equation of the magnetic state predicted by the scaling theory. The determined critical exponents agree well with those obtained from the results of the renormalization group theory approach for a three-dimensional Ising system coupled with a long-range interaction between spins decaying as $J(r)\ensuremath{\approx}{r}^{\ensuremath{-}(d+\ensuremath{\sigma})}$ with $\ensuremath{\sigma}$ = 1.84. The Ising-type spin state in ${\mathrm{Mn}}_{1/4}{\mathrm{NbS}}_{2}$ is attributed to the higher size of MAE. Our theoretical analysis shows that indirect exchange interaction between Mn-Mn along the $c$ axis, mediated via spins' polarized conduction electrons of Nb atoms, a Ruderman-Kittel-Kasuya-Yoshida (RKKY) type ferromagnetic interaction, dominates over the direct in-plane Mn-Mn exchange interaction (less favorable due to large ${d}_{\text{Mn-Mn}}\ensuremath{\sim}6.67\phantom{\rule{4pt}{0ex}}\stackrel{\ifmmode \mathring{}\else \r{}\fi{}}{\mathrm{A}}$) and is thus responsible for the macroscopic magnetization in ${\mathrm{Mn}}_{1/4}{\mathrm{NbS}}_{2}$. The RKKY-type ferromagnetic interaction in ${\mathrm{Mn}}_{1/4}{\mathrm{NbS}}_{2}$ arises due to the large spin polarization of the conduction electrons associated with the Nb atoms at the Fermi energy and existence of unoccupied Mn $3d$ states well above the Fermi level.

Magnetic array for efficient and stable Flow-electrode capacitive deionization

Magnetic flow-electrode capacitive deionization (FCDI) is a promising desalination technology; however, it still faces the risk of material stability and flow channel clogging during continuous operation. In this study, a new magnetic array design was introduced in the FCDI system to achieve efficient and stable desalination. Pairs of magnets were uniformly placed on the surface of the end plates along the flow channel to create alternating magnetic and magnetic field-free zones. Core-shell magnetic carbon (MC) was used as the conductive additive to guide the flow electrodes towards the magnet sides, thus creating a high concentration electrode area on the surface of the current collectors. When the flow electrode entered the magnetic field-free zones, the concentrated flow electrode returned to a homogeneous state. The results demonstrated that the desalination rate of FCDI with a low carbon content (1.0–2.0 wt%) increased by more than 120% after the application of a magnetic field. In the magnetic array, the working surface of the current collector significantly increased due to the aggregation effect of MC particles, which improved the electron transfer efficient and shortened the ion transport distance. In addition, the operational stability of FCDI in the magnetic field array was also demonstrated in a long-term operation. When the cell voltage was 1.2 V, the average salt removal rate (ASRR) and charge efficiency of FCDI were maintained at 0.35 μmol cm−2·min−1 and greater than 95%, respectively. In summary, magnetic array design offers the potential for FCDI to break through the trade-off between desalination performance and pumping energy consumption.

Combined analysis of remote sensing, gravity and magnetic data across Moyar Bhavani Shear Zone, Southern Granulite Terrane (SGT), India: appraisals for crustal architecture and tectonics

We present a combined analysis of remote sensing, gravity and magnetic data across Moyar Bhavani Shear Zone (MBSZ), Southern Granulite Terrane (SGT), India to study crustal architecture and tectonics. The horizontal gradient of gravity data shows strong density inhomogeneity across the MBSZ. The magnetic data and residual gravity analysis shows corroboration of a NE–SW trending linear magnetic anomaly zone and residual gravity high strip along the MBSZ. The low magnetic anomalies dominate the northern part of the MBSZ, while the southern part is dominated by moderate to high anomalies. The integration of potential data and remote sensing data clearly reveals that ENE–WSW is the dominant structural trend that coincides with the Mettur Shear Zone (MeSZ) trend. The joint gravity and magnetic modelling suggest that the MBSZ, is characterized by the disposition of mélange of moderate to high-density rocks of diamagnetic nature.

Easy axis anisotropy creating high contrast magnetic zones on magnetic tunnel junctions based molecular spintronics devices (MTJMSD)

Magnetic tunnel junction-based molecular spintronics device (MTJMSD) may enable novel magnetic metamaterials by chemically bonding magnetic molecules and ferromagnets (FM) with a vast range of magnetic anisotropy. MTJMSD have experimentally shown intriguing microscopic phenomenon such as the development of highly contrasting magnetic phases on a ferromagnetic electrode at room temperature. This paper focuses on Monte Carlo Simulations (MCS) on MTJMSD to understand the potential mechanism and explore fundamental knowledge about the impact of magnetic anisotropy. The selection of MCS is based on our prior study showing the potential of MCS in explaining experimental results (Tyagi et al. in Nanotechnology 26:305602, 2015). In this paper, MCS is carried out on the 3D Heisenberg model of cross-junction-shaped MTJMSDs. Our research represents the experimentally studied cross-junction-shaped MTJMSD where paramagnetic molecules are covalently bonded between two FM electrodes along the exposed side edges of the magnetic tunnel junction (MTJ). We have studied atomistic MTJMSDs properties by simulating a wide range of easy-axis anisotropy for the case of experimentally observed predominant molecule-induced strong antiferromagnetic coupling. Our study focused on understanding the effect of anisotropy of the FM electrodes on the overall MTJMSDs at various temperatures. This study shows that the multiple domains of opposite spins start to appear on an FM electrode as the easy-axis anisotropy increases. Interestingly, MCS results resembled the experimentally observed highly contrasted magnetic zones on the ferromagnetic electrodes of MTJMSD. The magnetic phases with starkly different spins were observed around the molecular junction on the FM electrode with high anisotropy.

Predictors of disparity between targeted and in-zone systematic cores during transrectal MR/US-fusion prostate biopsy.

The combination of targeted and systematic biopsies during MR/US-fusion prostate biopsy improves cancer detection over either modality alone. To identify factors associated with disparity in detection of prostate cancer between systematic and targeted biopsies in magnetic resonance imaging positive zones. We retrospectively analyzed 171 men receiving initial MR/US fusion biopsy at our institution from 2015 to 2018. Disparity was defined as positive targeted but negative systematic biopsy within an magnetic resonance imaging-positive zone (PIRADS 3+), or vice versa. Multivariable logistic regression was used to identify factors associated with disparity in detection of cancer on a per lesion basis. Three hundred and fifty-five lesions were targeted. For any cancer and clinically significant prostate cancer (csPCa), 37 (10%) and 24 (7%) lesions were target positive/systematic negative, respectively, while 30 (8%) and 23 (6%) lesions were target negative/systematic positive. In multivariable analysis, anterior location (OR 4.1, 95% CI 1.5-11.4, P = 0.007) was associated with csPCa target positive/systematic negative disparity, while higher prostate volume (OR 1.14, 95% CI 1.0-1.29, P = 0.04) was associated with csPCa target negative/systematic positive disparity. Shorter distance from apex (OR 1.02, 95% CI 1.01-1.04, P = 0.02) was associated with target positive/systematic negative disparity for any cancer. Limitations included relatively limited sample size and lack of prostatectomy specimen as a gold standard. Anterior or apical lesion location favors better disease capture on targeted biopsies. When doing systematic-only biopsies, surgeons may consider sampling the anterior zone separately.

Are low-frequency quasi-periodic oscillations in accretion flows the disk response to jet instability?

Low-frequency quasi-periodic oscillations, or LFQPOs, are ubiquitous in black hole X-ray binaries and provide strong constraints on the accretion-ejection processes. Although several models have been proposed, none has been proven to reproduce all observational constraints, and no consensus has emerged so far. We make the conjecture that disks in binaries are threaded by a large-scale vertical magnetic field that splits it into two radial zones. In the inner jet-emitting disk (JED), a near equipartition field allows driving powerful self-collimated jets, while beyond a transition radius, the disk magnetization is too low and a standard accretion disk (SAD) is settled. In a series of papers, this hybrid JED-SAD disk configuration has been shown to successfully reproduce most multiwavelength (radio and X-rays) observations, as well as the concurrence with the LFQPOs for the archetypal source GX 339-4. We first analyze the main QPO scenarios provided in the literature: (1) a specific process occurring at the transition radius, (2) the accretion-ejection instability, and (3) the solid-body Lense-Thirring disk precession. We recall their main assumptions and shed light on some severe theoretical issues that question the capability of reproducing LFQPOs. We then argue that none of these models can be operating under JED-SAD physical conditions. We finally propose an alternative scenario according to which LFQPOs are the disk response to an instability triggered in the jets near a magnetic recollimation zone. This situation can account for most of the type C QPO phenomenology and is consistent with the global behavior of black hole binaries. This nondestructive jet instability remains to be calculated, however. If this instability is numerically confirmed, then it might also naturally account for the jet wobbling phenomenology seen in various accreting sources such as compact objets and young forming stars.

A Study of Physical Modeling and Mathematical Modeling on Inclusion Behavior in a Planar Flow Casting Process

Flow pattern and inclusion removal in a novel-designed crucible in the planar flow casting process were studied in the present paper. A color dye water experiment was used to show the flow field and validate the mathematical modeling. It was shown that the flow pattern predicted by the Large Eddy Simulation model is maximally consistent with that in the physical modeling. The validated mathematical model was used to predict the flow pattern and inclusion behavior in the crucible with various prototypes using combinations of multiple facilities. The results show that the flow field, by using the stopper, enhances compared to that using none of the facilities, which causes the inclusion removal to become even worse when the stopper is individually used. Furthermore, as the magnetic field is added, the electromagnetic brake weakens the flow field in the magnetic zone. The function of the electromagnetic brake to weaken the flow pattern is most efficient for inclusion removal.

Octagonal Three-Dimensional Shim Coils Structure and Design in Atomic Sensors for Magnetic Field Detection

Triaxial uniform coils installed in the magnetically shielded cylinder are essential components of an atomic magnetometer to achieve ultra-sensitive measurements and are used to compensate for the ambient magnetic remanence in the magnetometer’s operating area. This paper proposes the new three-dimensional octagonal coils configured with a two-pair octagonal coil and two double-nested octagonal coils, which differs from the conventional square or circular shim coils. The spatially homogeneous distribution of the magnetic field of the three-dimensional shim coils based on this configuration is simulated and evaluated, and then the fabrication and experimental tests are completed. The theoretical calculation results show that the magnetic field uniformity of the z-direction two-pair octagonal coil is improved by about one order of magnitude compared with that of the conventional coil such as the Lee-Whiting coil and the Rubens coil. The magnetic field uniformity of x-direction or y-direction double nested octagonal coil is promoted by about two orders of magnitude compared with that of saddle coil. The experimental magnetic field distribution is consistent with the theoretical value. This configuration can reduce the outer diameter of the coil under the premise of meeting the requirement of setting the magnetic field uniform zone, and it is easier to install than the cylindrical coil assemblies.

Antiferromagnetic excitonic insulator state in Sr3Ir2O7

Excitonic insulators are usually considered to form via the condensation of a soft charge mode of bound electron-hole pairs. This, however, presumes that the soft exciton is of spin-singlet character. Early theoretical considerations have also predicted a very distinct scenario, in which the condensation of magnetic excitons results in an antiferromagnetic excitonic insulator state. Here we report resonant inelastic x-ray scattering (RIXS) measurements of Sr3Ir2O7. By isolating the longitudinal component of the spectra, we identify a magnetic mode that is well-defined at the magnetic and structural Brillouin zone centers, but which merges with the electronic continuum in between these high symmetry points and which decays upon heating concurrent with a decrease in the material’s resistivity. We show that a bilayer Hubbard model, in which electron-hole pairs are bound by exchange interactions, consistently explains all the electronic and magnetic properties of Sr3Ir2O7 indicating that this material is a realization of the long-predicted antiferromagnetic excitonic insulator phase.