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- electromagnetic pulse
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- Southern University of Science and Technology
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- V.N. Karazin Kharkiv National University
- Politecnico di Torino
- Centro de laseres pulsados and University of Salamanca
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[IEEE 2018 XXIIIrd International Seminar/Workshop on Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory (DIPED) - Tbilisi, Georgia (2018.9.24-2018.9.27)] 2018 XXIIIrd International Seminar/Workshop on Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory (DIPED) - Magnetometry and NMR Study of Carbon Nanopowders Doped with Cobalt Nanoclusters and Self-assembly of their Polymer Nanocomposites under Magnetic Field
摘要： The RF resonant magnetometry and NMR studies were carried out on carbon nanoparticles doped with magnetic cobalt clusters, which were synthesized by a technology combining of the hydrocarbon vapor pyrolysis and the chemical vapor deposition (CVD) process in a horizontal continuous reactor. The RF resonant magnetometry data show that the obtained carbon cobalt nanopowders are superparamagnetic at room temperatures and ferromagnetic at liquid nitrogen temperatures. The NMR study with the excitation by additional magnetic video-pulses of nanopowders obtained by using different hydrocarbons pyrolysis made it possible a fast assessment of their magnetic phase and hardness properties. The simple non-contact RF resonant magnetometry study of self-assembling processes in carbon cobalt polymer composite films synthesized using these nanopowders was made also.
关键词： magnetic nanoclusters,carbon nanopowder,core-shell structure,self-assembly,NMR,cobalt
更新于2025-09-04 15:30:14
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Initial experience of correlating diffusion spectral parameters with histopathologic indexes in murine colorectal tumor homografts
摘要： Purpose: To determine the correlation between continuously distributed diffusion-weighted image (DWI)-derived parameters and histopathologic indexes. Methods: Fifty-four mice bearing HCT-116 colorectal tumors were included for analysis; 12 mice were used for continuous observation, and the other 42 mice were used for break-point observation. All mice were randomly divided into radiotherapy and non-radiotherapy groups. Optical imaging and MRI were performed at different time points according to radiotherapy regimen (baseline, 24 h, 48 h, 72 h, 7 d, 14 d, and 28 d). Continuous observation data were analyzed to show the difference of dynamic changing trends of optical and MR-DWI–derived parameters between radiotherapy and non-radiotherapy groups (photon numbers, D_max, full width half maximum [FWHM], and apparent diffusion coefficient [ADC] value). Break-point observation data were used to analyze the correlation between histopathologic indices and DWI-derived parameters. Results: There was a significant difference in the changing trends of photon numbers, D_max, FWHM, and ADC value between radiotherapy and non-radiotherapy groups, especially at early time points. There was moderate negative correlation between Ki67 and percentage changes of D_max, FWHM, and ADC values (the correlation coefficients were 0.632, 0.449, and 0.586, P,0.001, P=0.008, and P,0.001, respectively). There was moderate negative correlation between survivin and percentage changes of D_max and ADC values (correlation coefficients were 0.496 and 0.473, P=0.004 and P=0.006, respectively). Conclusion: The continuously distributed DWI-derived parameters could reflect histological behavior to some extent and, thus, are potential markers for early noninvasive monitoring of tumor cell apoptosis and proliferation.
关键词： magnetic resonance imaging,colorectal cancer,murine homografts,diffusion-weighted imaging,continuously distributed
更新于2025-09-04 15:30:14
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Propagating Spectropolarimetric Disturbances in a Large Sunspot
摘要： We present results derived from the analysis of spectropolarimetric measurements of active region AR12546, which represents one of the largest sunspots to have emerged onto the solar surface over the last 20 years. The region was observed with full-Stokes scans of the Fe I 617.3 nm and Ca II 854.2 nm lines with the Interferometric BIdimensional Spectrometer instrument at the Dunn Solar Telescope over an uncommon, extremely long time interval exceeding three hours. Clear circular polarization (CP) oscillations localized at the umbra–penumbra boundary of the observed region were detected. Furthermore, the multi-height data allowed us to detect the downward propagation of both CP and intensity disturbances at 2.5–3 mHz, which was identi?ed by a phase delay between these two quantities. These results are interpreted as a propagating magnetohydrodynamic surface mode in the observed sunspot.
关键词： Sun: photosphere,Sun: chromosphere,polarization,Sun: magnetic ?elds,Sun: oscillations,sunspots
更新于2025-09-04 15:30:14
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Sorting and manipulation of biological cells and the prospects for using optical forces
摘要： Contemporary biomedical research requires development of novel techniques for sorting and manipulation of cells within the framework of a microfluidic chip. The desired functions of a microfluidic chip are achieved by combining and integrating passive methods that utilize the channel geometry and structure, as well as active methods that include magnetic, electrical, acoustic and optical forces. Application of magnetic, electric and acoustics-based methods for sorting and manipulation have been and are under continuous scrutiny. Optics-based methods, in contrast, have not been explored to the same extent as other methods, since they attracted insufficient attention. This is due to the complicated, expensive and bulky setup required for carrying out such studies. However, advances in optical beam shaping and computer hardware, and software have opened up new opportunities for application of light to development of advanced sorting and manipulation techniques. This review outlines contemporary techniques for cell sorting and manipulation, and provides an in-depth view into the existing and prospective uses of light for cell sorting and manipulation.
关键词： Cell manipulation,Optical sorting,Microfluidics,Acoustic sorting,Cell separation,Dielectrophoresis,Magnetic manipulation
更新于2025-09-04 15:30:14
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Layered Topological Insulators and Semimetals for?Magnetoresistance Type Sensors
摘要： Magnetoresistance (MR) type sensors are transducers that can vary their resistances sensitively in response to an applied magnetic field. Recently, topological quantum materials have drawn the increased attention for sensor applications due to their novel MR effects. Here, a range of MR effects occurring in the layered 3D topological insulators and topological semimetals are briefly reviewed. The MR effects include the extremely large nonsaturating MR, the giant anisotropic MR, and the unique spin-valve-like MR. The large MR ratios, the high MR anisotropy, and the low 1/f noise allow sensors to have the high sensitivity over a wide range of temperatures and magnetic fields. It is anticipated that the layered topological quantum materials with their excellent MR performance and structural flexibility would provide an ideal platform for new-generation magnetic sensor applications.
关键词： anisotropic magnetoresistance,magnetic sensors,topological quantum materials,linear magnetoresistance,tunneling magnetoresistance
更新于2025-09-04 15:30:14
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VALIDATION OF A CONVOLUTION INTEGRAL FOR CONDUCTIVITY IMAGING
摘要： Magnetic induction tomography has been under consideration for imaging electrical conductivity distributions within the human body. Multi-coil systems are most commonly employed for this task, requiring a numerical solution of Maxwell’s equations at each position of the coil array. An alternative uses a single coil placed near the conductive target while measuring coil self-impedance changes at a number of unique locations. Recently, a closed-form solution of Maxwell’s equations, in the form of a 3D convolution integral, was found for a single coil consisting of concentric circular loops that relates impedance change (loss) to an arbitrary conductivity. Its development required spatially uniform permittivity and permeability, yet showed quantitative agreement with experiment. Here, we provide a much more rigorous test of the convolution integral in experiments that allow large permittivity changes across coil dimensions. Loss is measured while the coil is placed at known positions relative to plastic columns of variable diameter which are ?lled with salt solutions of varying conductivity. In all cases, coil loss varies linearly with conductivity and with zero intercept. Quantitative agreement is observed only when column diameter is greater than or equal to coil diameter. Because of linearity, the convolution integral is useful for image reconstruction, though contrast could be either reduced or enhanced in those circumstances when relative permittivity change exceeds ～ 70.
关键词： single-coil system,conductivity imaging,convolution integral,Maxwell’s equations,Magnetic induction tomography
更新于2025-09-04 15:30:14
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Evaluation of renal dysfunction using texture analysis based on DWI, BOLD, and susceptibility-weighted imaging
摘要： Objective To explore the value of texture analysis based on diffusion-weighted imaging (DWI), blood oxygen level–dependent MRI (BOLD), and susceptibility-weighted imaging (SWI) in evaluating renal dysfunction. Methods Seventy-two patients (mean age 53.72 ± 13.46 years) underwent MRI consisting of DWI, BOLD, and SWI. According to their estimated glomerular filtration rate (eGFR), the patients were classified into either severe renal function impairment (sRI, eGFR < 30 mL/min/1.73 m2), non-severe renal function impairment (non-sRI, eGFR ≥ 30 mL/min/1.73 m2, and < 80 mL/min/1.73 m2), or control (CG, eGFR ≥ 80 mL/min/1.73 m2) groups. Thirteen texture features were extracted and then were analyzed to select the most valuable for discerning the three groups with each imaging method. A ROC curve was performed to compare the capacities of the features to differentiate non-sRI from sRI or CG. Results Six features proved to be the most valuable for assessing renal dysfunction: 0.25QuantileDWI, 0.5QuantileDWI, HomogeneityDWI, EntropyBOLD, SkewnessSWI, and CorrelationSWI. Three features derived from DWI (0.25QuantileDWI, 0.5QuantileDWI, and HomogeneityDWI) were smaller in sRI than in non-sRI; EntropyBOLD and CorrelationSWI were smaller in non-sRI than in CG (p < 0.05). 0.25QuantileDWI, 0.5QuantileDWI, and HomogeneityDWI showed similar capacities for differentiating sRI from non-sRI. Similarly, EntropyBOLD and CorrelationSWI showed equal capacities for differentiating non-sRI from CG. Conclusion Texture analysis based on DWI, BOLD, and SWI can assist in assessing renal dysfunction, and texture features based on BOLD and SWI may be suitable for assessing renal dysfunction during early stages.
关键词： Chronic kidney disease,Image processing, computer-assisted,Diffusion magnetic resonance imaging,Chronic renal insufficiency
更新于2025-09-04 15:30:14
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QED Phenomena in an Ultrastrong Magnetic Field. I. Electron–Photon Scattering, Pair Creation, and Annihilation
摘要： We evaluate several basic electrodynamic processes as modi?ed by the presence of a very strong magnetic ?eld, exceeding 10^13 G. These results are needed to build models of dissipative phenomena outside magnetars and some other neutron stars. Differential and total cross sections and rates are presented for electron–photon scattering, the annihilation of an electron–positron pair into two photons, the inverse process of two-photon pair creation, and single-photon pair creation into the lowest Landau state. The relative importance of these interactions changes as the background magnetic ?eld grows in strength. The particle phase space relevant for a given process may be restricted by single-photon pair creation, which also opens up ef?cient channels for pair multiplication, e.g., in combination with scattering. Our results are presented in the form of compact formulae that allow for relativistic electron (positron) motion, in the regime where Landau excitations can be neglected (corresponding to 10^3B_Q ? B ? B_Q for moderately relativistic motion along the magnetic ?eld). Where a direct comparison is possible, our results are tested against earlier calculations, and a brief astrophysical context is provided. A companion paper considers electron–positron scattering, scattering of electrons and positrons by ions, and relativistic electron–ion bremsstrahlung.
关键词： magnetic ?elds,radiation mechanisms: general,relativistic processes,scattering,stars: magnetars
更新于2025-09-04 15:30:14
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Perpendicular magnetic anisotropy and its electric field effect in Co ultrathin films deposited directly on SrTiO <sub/>3</sub> (111) surface
摘要： We have investigated magnetic anisotropy and its electric ?eld e?ect in ultrathin Co with a Pt cap layer. The layers were directly deposited on SrTiO3(111) and (100) surfaces without any under layer. In as-deposited samples, a stronger perpendicular magnetic anisotropy was observed in the (111) sample. A back gate con?guration was used to apply the electric ?eld to the bottom surface of Co layer through the SrTiO3 substrate. In both samples, the coercivity was enhanced with a positive gate bias, which corresponds to the direction of the electron accumulation. The e?ciency of the change in the coercivity per modulated electron density was greater in the (111) sample over a wide temperature range including 2 K, at which the thermally activated magnetization reversal was expected to be suppressed. The results suggest that the surface orientation of the substrate a?ects both the magnetic anisotropy and its electric ?eld e?ect on Co.
关键词： perpendicular magnetic anisotropy,SrTiO3,Co ultrathin ?lms,electric ?eld e?ect
更新于2025-09-04 15:30:14
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Holographic interferometric microscopy for measuring Cu2+ concentration profile during Cu electrodeposition in a magnetic field
摘要： We measured the concentration boundary layer during copper electrodeposition in a copper sulfate solution under an applied magnetic field. Using a holographic laser interference microscope, we demonstrated the formation of the diffusion layer near the cathode. In the initial stage of electrodeposition, the diffusion layer was distorted in a magnetic field. An analysis of the electrode surface concentration supported the following assertions: without a magnetic field, dendrites formed when the surface concentration of Cu2+ was depleted; with a magnetic field, the unique convection phenomena of the field gradient force and localized Lorentz force promoted Cu2+ mass transport in the diffusion layer, producing large crystal grains.
关键词： Diffusion layer,Magnetohydrodynamic,Magnetic field,Localized Lorentz force,Field gradient force
更新于2025-09-04 15:30:14