Location Of Magnetic Source Research Articles

Targeted delivery of therapeutic agents in a healthy and stenosed patient-specific carotid artery using an external magnetic field

In Magnetic Drug Targeting (MDT), an alternative and highly efficient technique to traditional drug delivery methods, therapeutic agents labeled with magnetic particles are transported to a target region using an external magnetic field. A high concentration of agents in the target tissue and their non-dispersion in the body increases treatment efficiency. In this study, targeted delivery of endothelial cells containing magnetic particles in a healthy and stenosed patient-specific carotid artery was studied. The Eulerian-Lagrangian approach was adapted to track the motion of particles and solve fluid equations. The effect of many internal parameters such as plaque morphology (occlusion percentage and the chord length of stenosis) and external parameters such as the strength and the position of the magnetic source, injection time, and the mass of magnetic particles inside each cell on the capture efficiency (CE) of cells was investigated. Results reveal that increasing the mass of magnetic particles in each cell and magnetic field strength enhances the capture efficiency of cells in the target region. Also, shifting the magnetic source location from position 1 (before the carotid sinus) to position 3 (after the carotid sinus) can increase and decrease the number of absorbed cells in the target region and CCA, respectively, both of which are desirable. Investigation of the injection time shows that the CE of cells when injecting in the systole and diastole is approximately the same as their CE when injected in a whole cardiac cycle. For a stenosed carotid artery, the percentage of occlusion is directly related to the CE of cells in the target region. Also, the chord length of stenosis has a direct and inverse relationship with the number of absorbed cells on the plaque surface and in the target region, respectively. Therefore, magnetic particles with higher magnetism or stronger magnetic fields are recommended for the stenosed carotid artery with a more severe occlusion percentage or a longer chord length.

Influence and remedial measures of missing test data on magnetic field source location of underwater vehicle

Due to the incomplete data collected, it will increase the difficulty of inversion location in the field source inversion of the static magnetic field data of underwater vehicles. Therefore, it is very necessary to study the influence of data loss on the static magnetic source location of underwater vehicles and the field source location for timely remedy of missing data. In this paper, the static magnetic equivalent source model of underwater vehicle was established. Then the inversion positioning algorithm was used to locate the magnetic field source of the underwater vehicle obtained from the test, and the influence of the location result under the incomplete data information was analyzed. We used deleting method, linear interpolation method and sliding filling method to populate the data to fill the remedy of missing data. Using the localization algorithm to carried out the inversion location of source, then we took the location of source inversion and the size of the magnetic dipole moment to the ellipsoid model to get fitting curve of magnetic field. The simulation curve of contrast verification test data with experimental data and the lack of remedial method was feasible. The results show that the missing data can not be ignored for the location of the underwater vehicle’s magnetic field source, and the data pairs filled with missing data can be effectively located for the equivalent static magnetic field source of the underwater vehicle through using deletion method, linear interpolation method and sliding filling method.

Subsurface Tectonic Inferences of the Adamawa Region of Cameroon from EMAG2 Magnetic Data

The study area includes an area between 6° to 8°N and 11° to 15°E. Geologically, it belongs to Precambrian basement (granites, gneisses), Proterozoic, and Archean (volcanic) series, showing the main heat sources of Cameroon. The purpose of this study deals to analyze and interpret the EMAG2 magnetic data in the Adamawa area using various advanced processing techniques. Thus, the mapping and depth estimation of underground structures are realized. The analysis of aeromagnetic map of the reduction to equator (RTE) in Adamawa area reveals rapidly evolving subsurface geological presented its lithological and structural. In the same, the power spectrum-processing tool clearly emphasizes shallow and deep underground heat sources. Two magnetic source location methods (source parameter imaging and analytical signal) are used to characterize of the source. The estimated magnetic source depths from source parameter imaging (SPI) are between 0.3 km and 22 km. The analytical signal ranges from 0.2 km to 31 km. In addition, the comparative study of 2D magnetic modelling showed that the basement is affected by the faults in the main directions of N-S, NE-SW, NW-SE, and WNW-ESE. The resulting structural map based on the tectonic map of Adamawa magnetic basement is a document that can simplify future hydrological and geothermal exploration.

Natural convection in a sinusoidally heated cavity filled with ferrofluid in the presence of partial variable magnetic field

PurposeThe purpose of this study is to investigate partial magnetic source (MS) effect on natural convection (NC) flow of a ferrofluid flow in a cavity with sinusoidally heated vertical walls. The combination of ferrohydrodynamics and magnetohydrodynamics due to the variable magnetic field (MF) and magnetite nanoparticles in one part of the cavity, and the classical NC in the other part of the cavity are concerned.Design/methodology/approachThe dimensionless equations in stream function-vorticity form are numerically solved by radial basis functions (RBF) based collocation method.FindingsA remarkable change in fluid flow and heat transfer is noted if the MS location is close to the left sinusoidally heated wall. In particular, the average Nusselt number is the smallest for the middle centered partial MF through the left wall at a large Hartmann number.Research limitations/implicationsRBF collocation approach is limited to small geometries due to the obtained solution globally in the entire domain of the problem.Practical implicationsIf the partial restriction of the effect of MF is done in real life, it would be a control parameter at some required/requested areas of the concerned problem.Social implicationsThis is a physical problem.Originality/valueIf the proposed idea of partial variable MF is able to be applied to a system in real life, it would be a good controller on fluid flow and heat transfer. RBF-based methods are also alternative numerical procedures to solve heat transfer and fluid flow problems.

Aeromagnetic anomalies and magnetic domains of the Jalisco Block, western Mexico

The Jalisco Block (JB) in western Mexico has been considered as a margin terrane being detached from the North American plate along the Tepic-Zacoalco rift and Colima graben. In this study, an aeromagnetic analysis of the JB and surrounding areas is performed applying a series of geophysical filters and VOXI inverse model. The JB is characterized by two aeromagnetic domains (AMD). AMD-Ia located throughout the south-central section that borders the continental margin is characterized by positive magnetic anomalies extending from the Armería river to Banderas Bay. The AMD-Ia corresponds to the Puerto Vallarta batholith emplaced in the late Cretaceous. The AMD-IIa in the northern section is marked by negative magnetic anomalies over volcanic and volcano-sedimentary rocks, extending to the southern Sierra Madre Occidental. We propose that JB tectonic boundaries correspond to the aeromagnetic AMD-Ia eastern limit and AMD-IIa northern limit. Estimated depths from the radially average power spectrum for deep magnetic sources in the AMD-Ia are in the range of 5.4 km, and for shallow sources from 0.8 to 1.2 km. For AMD-IIa depths are 10.45 km for deep sources and 0.13 km for shallow sources. Depths for deep sources from the Euler deconvolution for the AMD-Ia range from 3.3 to 4.5 km and from 3.5 to 4.9 km for the AMD-IIa. Shallow source depths in the AMD-Ia are 0.2–0.3 km and near surface for the AMD-IIa. The integrated analysis shows five aeromagnetic domains, two associated with the JB and three with the surrounding areas. The VOXI inverse model allows to estimate the dimensions and location of magnetic sources in the reduced to the pole and upward continuations.

Experimental investigation on the Euler-type location and orientation algorithm using magnetic field and its gradient tensor

The magnetic source location has wide application prospects in the fields of space exploration, non-destructive testing, security monitoring and target tracking. A constrained Euler location algorithm is applied to the location of a small current-carrying multi-turn ring coil, which is the closed analytic form of the position solution. The error of position solution for the traditional Euler location algorithm is deduced analytically. An experimental device of three-axis fluxgate magnetometer (TAFM) cross-array is constructed. The interference of ambient magnetic field is filtered from the magnetic data by the digital band-pass filter, and the magnetic field of the multi-turn coil is restructured by the least-squares fitting. The Euler and constrained Euler location algorithms are compared with the numerical simulation and the experimental data, and the results show that the constrained Euler location precision of the location algorithm is better than the Euler one. And more, experimental tests verify that the relative error of position solution is less than 10% for the two location algorithms in the given distance range.

Impact of Antiepileptic Drugs on Cognition and Neuromagnetic Activity in Childhood Epilepsy With Centrotemporal Spikes: A Magnetoencephalography Study.

Objective: Childhood epilepsy with centrotemporal spikes (CECTS), the most common childhood epilepsy, still lacks longitudinal imaging studies involving antiepileptic drugs (AEDs). In order to examine the effect of AEDs on cognition and brain activity. We investigated the neuromagnetic activities and cognitive profile in children with CECTS before and after 1 year of treatment.Methods: Fifteen children with CECTS aged 6–12 years underwent high-sampling magnetoencephalography (MEG) recordings before treatment and at 1 year after treatment, and 12 completed the cognitive assessment (The Wechsler Intelligence Scale for Children). Next, magnetic source location and functional connectivity (FC) were investigated in order to characterize interictal neuromagnetic activity in the seven frequency sub-bands, including: delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), gamma (30–80 Hz), ripple (80–250 Hz), and fast ripple (250–500 Hz).Results: After 1 year of treatment, children with CECTS had increased scores on full-scale intelligence quotient, verbal comprehension index (VCI) and perceptual reasoning index (PRI). Alterations of neural activity occurred in specific frequency bands. Source location, in the 30–80 Hz frequency band, was significantly increased in the posterior cingulate cortex (PCC) after treatment. Moreover, FC analysis demonstrated that after treatment, the connectivity between the PCC and the medial frontal cortex (MFC) was enhanced in the 8–12 Hz frequency band. Additionally, the whole-brain network distribution was more dispersed in the 80–250 Hz frequency band.Conclusion: Intrinsic neural activity has frequency-dependent characteristic. AEDs have impact on regional activity and FC of the default mode network (DMN). Normalization of aberrant DMN in children with CECTS after treatment is likely the reason for improvement of cognitive function.

Impacts of variable magnetic field on a ferrofluid flow inside a cavity including a helix using ISPH method

Purpose The purpose of this paper is to study the unsteady ferrofluid flow with a hot source helix inside a cavity under the impacts of a variable magnetic field by using the incompressible smoothed particle hydrodynamics method. Design/methodology/approach The governing equations are formulated by considering the basics of the magnetohydrodynamic and ferrohydrodynamics. Different locations of a variable magnetic source outside the geometry are investigated. The helical coils are extensively applied in the cooling and heating of air conditioners and heat pumps. Computations were carried out for different lengths of the heated helix (0.2 ≤ Lh ≤ 0.8), different locations of the magnetic source, (a = 0.5, b = −0.01), (a = 0.5, b = 1.01), (a = 1.01, b = 0.5), (a = −0.01, b = 0.5), different numbers of the inner helix (one helix, two helixes and three helixes) and different values of the nanoparticles volume fraction (0% ≤ ϕ ≤ 10%). Findings The outcomes of the investigations revealed that an increase in the lengths of a helix by 0.4 results in a reduction of the stream function by 25.60%. In addition, when the magnetic wire is located near the center of the right wall, the maximum values of the average Nusselt number are obtained while the smallest values of the average Nusselt number are given when the magnetic source is located near center of the top wall. Originality/value The novelty of this paper is investigating the natural convection flow from two different models of an inner hot helix inside a cavity with considering different locations of variable magnetic sources.

A New Theoretical Approach of Wall Transpiration in the Cavity Flow of the Ferrofluids.

An idea of permeable (suction/injection) chamber is proposed in the current work to control the secondary vortices appearing in the well-known lid-driven cavity flow by means of the water based ferrofluids. The Rosensweig model is conveniently adopted for the mathematical analysis of the physical problem. The governing equation of model is first transformed into the vorticity transport equation. A special finite difference method in association with the successive over-relaxation method (SOR) is then employed to numerically simulate the flow behavior. The effects of intensity of magnetic source (controlled by the Stuart number), aspect ratio of the cavity, rate of permeability (i.e., ), ratio of speed of suction/injection to the sliding-speed of the upper wall of a cavity, and Reynolds number on the ferrofluid in the cavity are fully examined. It is found that the secondary vortices residing on the lower wall of the cavity are dissolved by the implementation of the suction/injection chamber. Their character is dependent on the rate of permeability. The intensity of magnetic source affects the system in such a way to alter the flow and to transport the fluid away from the magnetic source location. It also reduces the loading effects on the walls of the cavity. If the depth of cavity (or the aspect ratio) is increased, the secondary vortices join together to form a single secondary vortex. The number of secondary vortices is shown to increase if the Reynolds number is increased for both the clear fluid as well as the ferrofluids. The suction and injection create resistance in settlement of solid ferroparticles on the bottom. The results obtained are validated with the existing data in the literature and satisfactory agreement is observed. The presented problem may find applications in biomedical, pharmaceutical, and engineering industries.

Free Convection in a Wavy Walled Cavity With a Magnetic Source Using Radial Basis Functions

In this study, free convection in a cavity with differentially heated wavy walls is numerically investigated in the presence of a magnetic source. Polyharmonic spline radial basis function (RBF) is utilized to discretize the governing dimensionless equations formulated by stream function-vorticity. The effects of dimensionless Hartmann number, Rayleigh number, the number of undulations, amplitude of wave, and the location of magnetic source are visualized in streamlines and isotherms as well as calculating average Nusselt number through the heated wall. Results show that primary vortex in streamlines is altered with the impact of magnetic source. The augmentation of undulations and amplitude causes convective heat transfer to decrease if Ra = 105. The impact of location of magnetic source is noted close to the top wall.

Cross-sectional heat transfer of hot tubes in a wavy porous channel filled by Fe3O4-water nanofluid under a variable magnetic field

In this paper, the effect of porosity and variable magnetic field (VMF) on the natural convection heat transfer of Fe3O4-water nanofluid is studied in a wavy channel including hot tubes using the finite element method by FlexPDE commercial code. The upper and lower surfaces of the channel are wavy shaped and in low temperature and three hot tubes were located in the channel by equal distances. In this study, the effects of five main parameters (Darcy number (Da), Hartmann Number (Ha), nanoparticles volume fraction ( $ \varphi$ ), Rayleigh number (Ra) and magnetic source location (a)) on the local and average Nusselt numbers of the tube center and the wavy wall are investigated. As a main outcome, results confirm that the nanoparticles volume fraction plays the most important role on the Nusselt number among other parameters.

Physical effect of a variable magnetic field on the heat transfer of a nanofluid-based concentrating parabolic solar collector

In this paper, the physical effect of a variable magnetic field on a nanofluid-based concentrating parabolic solar collector (NCPSC) is demonstrated. A section of reservoir is modeled as a semi-circular cavity under the solar radiation with the magnetic source located in the center or out of the cavity and the governing equations were solved by the FlexPDE numerical software. The effect of four physical parameters, i.e., Hartmann Number (Ha), nanoparticles volume fraction ( $ \varphi$ , magnetic field strength ( $ \gamma$ and magnetic source location (b, on the Nusselt number is discussed. To find the interaction of these parameters and its effect on the heat transfer, a central composite design (CCD) is used and analysis is performed on the 25 experiments proposed by CCD. Analysis of variance (ANOVA) of the results reveals that increasing the Hartmann number decreases the Nusselt number due to the Lorentz force resulting from the presence of stronger magnetic field.

Correlation imaging method based on local wavenumber for interpreting magnetic data

Depth estimation is a general task in the interpretation of magnetic data, and local wavenumber is an effective tool to accomplish this task, but this method requires the structural index of causative source when applies it to compute the depth of the source, which is hard to obtain for an unknown area. In this paper, we suggested a correlation imaging method to interpret magnetic data, which uses the correlation coefficient of local wavenumber of real magnetic data and transformative local wavenumber of synthetic magnetic data generated by assumed source to estimate the location of the source, and this method does not require any priori information of the source and does not require solving any matrix. The computation steps as follows, first, we assume that the causative sources are distributed regularly as a rectangular grid, and then separately compute the correlation coefficient of the local wavenumber of real data and local wavenumber of the anomaly generated by each assumed source, and the correlation coefficient gets maximum when the location parameters of the assumed source are in accord with the true locations of real sources. The synthetic tested results show that this method can obtain the location of magnetic source effectively and correctly, and is insensitive to magnetization direction and noise. This method is also applied to measured magnetic data, and get the location parameters of the source.

Numerical Study of Natural Convection in a Ferrofluid-Filled Corrugated Cavity With Internal Heat Generation

In this paper, numerical simulations for the natural convection in a ferrofluid-filled corrugated cavity with internal heat generation under the influence of a magnetic dipole source were performed. The cavity is heated from below and cooled from above while vertical side walls are assumed to be adiabatic. A magnetic dipole source was located under the bottom heated wall. The governing equations were solved by Galerkin weighted residual finite-element formulation. The influence of external Rayleigh number (between 104 and 5 × 105), internal Rayleigh number (between 104 and 5 × 106), magnetic dipole strength (between 0 and 4), horizontal (between 0.2 and 0.8) and vertical (between −5 and −2) locations of the magnetic dipole source on fluid flow, and heat transfer are numerically investigated. It was observed that depending on heating mechanism (the external or internal heating), the presence of corrugation of the bottom wall either enhances or deteriorates the absolute value of the averaged heat transfer. The strength and locations of the magnetic dipole source affect the distribution of the flow and thermal patterns within the cavity for both flat and corrugated wall cavity. The net effect of the complicated interaction of the internal heating, external heating, and ferroconvection of magnetic source results in heat transfer enhancement with increasing values of magnetic dipole strength. Wall corrugation causes more enhancement of averaged heat transfer and this is more pronounced for low values of vertical location of magnetic source.

GEOPHYSICS BRIGHT SPOTS

Below I mention two papers in the November-December issue of Geophysics. One paper is on using full-azimuth AVO inversion for HTI models to characterize fracture zones in reservoir cap and seal rocks for a Canadian CO2 storage site; the other demonstrates improved estimation of magnetic source location using normalized magnetic strength in the presence of remanent magnetization.

SLORETA-qm for interictal MEG epileptic spike analysis: Comparison of location and quantity with equivalent dipole estimation

ObjectiveTo determine whether quantitative modification of a standardised low-resolution brain electromagnetic tomography (sLORETA-qm) could be used as a reliable tool for quantitative analysis of magnetoencephalography (MEG) for analysis of the interictal epileptic spike. To verify the performance of sLORETA-qm, magnetic source location and quantity were compared with the equivalent current dipole (ECD) method. MethodsA total of 50 sources from 10 patients with epilepsy were obtained. Analyses were performed after the MEG data were 3–70Hz band-pass filtered. Time points for analysis were selected referring to waveform patterns and the isofield contour map. With the same spherical model, source estimation was conducted with two methods of analysis: ECD and sLORETA-qm. Distance from the centre of the spherical model and intensities were compared between the methods. ResultsThere were no significant differences between the methods in the distance from the spherical model (paired t-test, p=0.8761). Source intensities between the methods were strongly correlated (Spearman’s Rho=0.9803, p<0.001). ConclusionssLORETA-qm was closely correlated with ECD concerning point source location and quantity in analysis of the interictal epileptic spike. SignificancesLORETA-qm is a reliable quantifiable method without arbitrariness for analysis of the interictal epileptic spike.

Sources of along-strike variation in magnetic anomalies related to intrasedimentary faults: A case study from the Rio Grande Rift, USA

Normal faults within sedimentary basins are commonly associated with subtle linear features in high-resolution, total magnetic intensity (TMI) data. Many of these anomalies arise from the tectonic juxtaposition of sedimentary units of differing magnetic properties. In detail, the anomalies can be quite variable in character, even along the strike of individual faults. To understand this variability, we examine the well-exposed San Ysidro Fault in the central Rio Grande Rift, USA, using detailed magnetic-property measurements, geophysical models based on geology, and Euler analysis. We find that along-strike anomaly variability arises mainly from (1) multi-levelled magnetic contrasts at the fault that are variably sampled by uneven levels of erosion, and to a lesser extent from (2) magnetic susceptibilities that vary along strike within individual units, and (3) variable throw and dip of the fault that produces differences in the extents to which contrasting units are in contact. The multi-levelled magnetic contrasts arise from the juxtaposition of different strata across the fault at discrete depths. Locations of magnetic sources along the fault estimated from Euler analysis of the TMI data reflect the variations in depths to the shallowest sources along strike. Variations in clustering of the Euler solutions suggest that the sources have variable geometry (structural index). The results at the San Ysidro Fault demonstrate the important and complex role of multi-level led magnetic sources in understanding anomalies associated with faulted geologic layers in general. The potential for multiple sources suggests that the use of simple model geometries to represent faults may not always be appropriate.

Potential-field signatures of buried Precambrian basement in the Western Canada Sedimentary Basin

An internally consistent, levelled compilation of magnetic data is derived for Alberta and northeastern British Columbia. With Bouguer gravity data, this compilation is used to refine the definition of Precambrian basement domains within the Western Canada Sedimentary Basin. Magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths. Automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation. The basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest, due mainly to the availability of new public-domain magnetic data and the more precise definition of domain boundaries, based on the magnetic source location maps. The Nahanni, Hottah, Chinchaga, Thorsby, Vulcan, and Kiskatinaw domains are weakly magnetic and characterized by magnetic sources that are paramagnetic, comprising low-susceptibility silicate minerals. All other domains are characterized by the presence of ferrimagnetic material, most likely magnetite, which has a sufficiently high susceptibility to produce measurable anomalies. The largest anomalies and magnetizations are found in the Fort Nelson, Fort Simpson, Buffalo Head, Talston, Ksituan, and Matzhiwin domains. Such large magnetizations are usually indicative of intermediate igneous rocks associated with magmatic arc environments. Moderate-amplitude anomalies and (or) magnetizations are characteristic of the Nova, Wabamun, Lacombe, Rimbey, Loverna, and Medicine Hat domains, suggesting the presence of ferrimagnetic basic and granitoid rocks. Within some of the moderately magnetic domains are areas of paramagnetic lithologies that produce no magnetic anomalies. The narrower regions of magnetic lows, such as the Thorsby, Kiskatinaw, and Vulcan domains, are interpreted as resulting from demagnetization effects accompanying collision. Since demagnetization zones are limited in areal extent, the wider, more extensive magnetic lows of the Chinchaga and Hottah domains likely result from a combination of boundary demagnetization and a lower bulk magnetization level of crustal lithologies present.

In‐ecliptic CIR‐associated energetic particle events and polar coronal hole structures: SOHO/COSTEP observations for the Whole Sun Month Campaign

The Solar and Heliospheric Observatory (SOHO), in halo orbit around the L1 Lagrangian point of the Sun‐Earth system, combines a unique set of instruments for studies of the Sun and the heliosphere. SOHO's Comprehensive Suprathermal and Energetic Particle Analyser measures in situ particles in the energy range 44 keV/particle to above 53 MeV/nucleon. For the time period of the Whole Sun Month Campaign in mid 1996 we have identified recurrent energetic particle intensity increases in association with corotating interaction regions (CIRs) in the energy range &lt;10 MeV. Solar wind measurements of the Wind spacecraft were used to estimate the corresponding magnetic source location in Carrington longitude for comparison of energetic particles with synoptic maps of the lower corona, derived from images of SOHO's Extreme‐ultraviolet Imaging Telescope. The comparison reveals a close relationship of latitudinal extensions of polar coronal holes, situated in regions up to 40° away from the ecliptic, with CIR‐associated in‐ecliptic particle events.

An estimation algorithm for neuromagnetic source distribution using MRI information

We present an estimation algorithm for the location of magnetic sources in the human brain using magnetic resonance imaging (MRI) information. MRI information is used for limiting the estimation region to the cortex and analyzing acquired results. Magnetic fields of the brain are due to neural activity. As there are many neurons on the cortex, we regard it as a prime candidate for source location. The cortex is extracted from MR images. We assume that the points on the extracted cortex are current dipoles, and all the acquired points are considered as candidate sources. We then perform the estimation by means of the multiple signal classification (MUSIC) method. This algorithm can be considered as a first step in the estimation of the parameters of magnetic sources in the human brain. The acquired results may be interpreted as candidate locations at which sources exist, We perform computer simulations and apply this algorithm to real human brain data.