Use of 3-D magnetic resonance electrical impedance tomography in detecting human cerebral stroke: a simulation study

We have developed a new three dimensional (3-D) conductivity imaging approach and have used it to detect human brain conductivity changes corresponding to acute cerebral stroke. The proposed Magnetic Resonance Electrical Impedance Tomography (MREIT) approach is based on the J-Substitution algorithm and is expanded to imaging 3-D subject conductivity distribution changes. Computer simulation studies have been conducted to evaluate the present MREIT imaging approach. Simulations of both types of cerebral stroke, hemorrhagic stroke and ischemic stroke, were performed on a four-sphere head model. Simulation results showed that the correlation coefficient (CC) and relative error (RE) between target and estimated conductivity distributions were 0.9245±0.0068 and 8.9997%±0.0084%, for hemorrhagic stroke, and 0.6748±0.0197 and 8.8986%±0.0089%, for ischemic stroke, when the SNR (signal-to-noise radio) of added GWN (Gaussian White Noise) was 40. The convergence characteristic was also evaluated according to the changes of CC and RE with different iteration numbers. The CC increases and RE decreases monotonously with the increasing number of iterations. The present simulation results show the feasibility of the proposed 3-D MREIT approach in hemorrhagic and ischemic stroke detection and suggest that the method may become a useful alternative in clinical diagnosis of acute cerebral stroke in humans.

Impedance and Magnetization Studies of Ultrafine Ni-Zn Ferrite

Ultrafine Ni0.5Zn0.5 Fe2O4 powder was prepared by PVA aided chemical method. The powder and sintered pellets were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and complex impedance (Cl) analysis. The particles are found to be in the size range of 15 to 26 nm for various annealing temperatures. The coercivity, saturation magnetisation, Neel temperature and electrical conductivity are found to vary with sintering time at 800℃ for the pellet samples. The variations in the above intrinsic properties are explained qualitatively

Analysis and suppression method of transformer no-load closing excitation inrush current

The primary winding of the transformer will generate large inrush current due to the saturation of iron core when an unloaded transformer is switched-on. The inrush current not only causes mechanical interaction force due to which the windings are damaged, but also induces the differential protection relays to operate incorrectly. In this paper, the mathematical model of unloaded single phase transformer in switch-on is analyzed; the computation formulas of the inrush current and its interruption angle are presented. The experiment investigation of single phase transformers with different capacities shows that the inrush current measurement result is consistent with theoretical analysis. The inrush current waveform is typically a steeple top waveform with high order harmonics and damping in one direction. In the same condition, large inrush current amplitude will be induced with smaller switching angle, larger residual flux and smaller saturation flux.

One Step Quick Detection of Cancer Cell Surface Marker by Integrated NiFe-based Magnetic Biosensing Cell Cultural Chip

RGD peptides has been used to detect cell surface integrin and direct clinical effective therapeutic drug selection. Herein we report that a quick one step detection of cell surface marker that was realized by a specially designed NiF e-based magnetic biosensing cell chip combined with functionalized magnetic nanoparticles. Magnetic nanoparticles with 20-30 nm in diameter were prepared by coprecipitation and modified with RGD-4C, and the resultant RGD-functionalized magnetic nanoparticles were used for targeting cancer cells cultured on the NiF e-based magnetic biosensing chip and distinguish the amount of cell surface receptor-integrin.Cell lines such as Calu3, Hela, A549, CaF br, HEK293 and HUVEC exhibiting different integrin expression were chosen as test samples. Calu3, Hela, HEK293 and HUVEC cells were successfully identified. This approach has advantages in the qualitative screening test. Compared with traditional method, it is fast, sensitive, low cost,easy-operative, and needs very little human intervention. The novel method has great potential in applications such as fast clinical cell surface marker detection, and diagnosis of early cancer, and can be easily extended to other biomedical applications based on molecular recognition.

Dielectric and Magnetic Properties of (1-x)CaTiO3-xNi0.5Zn0.5Fe2O4 Composite Ceramics

（1-x）CaTiO3-xNi0.5Zn0.5Fe2O4（0 x 1.0） composite ceramics were synthesized by a conventional solid state reaction method.The phase formation,microstructure,and dielectric and magnetic properties were investigated by X-ray diffraction,scanning electron microscopy,precision impedance analysis,and vibrating sample magnetometry,respectively.The results indicate that the composite ceramics are composed of both perovskite phase Ca TiO3 and spinel phase Ni0.5Zn0.5Fe2O4.The maximal relative density for 0.5CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics reaches 97.8%,as it has been sintered at the temperature of 1260 ℃ for 3 h.Dielectric constant and loss tangent of（1-x）CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics show dispersion in the low frequency range.Their phase transition temperature of the dielectric constant shifts to lower temperatures with the increase of Ni0.5Zn0.5Fe2O4 content.This phenomenon is attributed to that the phase transition temperature of CaTiO3 is higher than that of Ni0.5Zn0.5Fe2O4.The saturation magnetization of （1-x）CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics increases with the Ni0.5Zn0.5Fe2O4 ferrite content.

Spray granulation of Fe and C nanoparticles and their impedance match for microwave absorption

The microwave absorbents of Fe and C nanoparticles as magnetic loss and dielectric loss material respectively were composited with the polyvinyl alcohol （PVA） as binder by spray granulation method, The electromagnetic parameters of Fe and C composite particles were analyzed by vector network. The complex permittivity and magnetic permeability of Fe and C composite particles matched well with increasing C nanoparticle content, and then the microwave loss property was improved. A minimum reflection loss （RL） of -42.7 dB at 3.68 GHz for a composite with 4.6 mm in thickness can be obtained when the content ratio of the C nanoparticles, the modified Fe nanoparticles and the PVA is 21：49：30 （Sample 3）.

Magnetic, Dielectric and Complex Impedance Properties of xBa_(0.95)Sr_(0.05)TiO_3–(1-x)BiFe_(0.9)Gd_(0.1)O_3Multiferroic Ceramics

xBa_（0.95）Sr_（0.05）TiO_3–（1-x）BiFe_（0.9）Gd_（0.1）O_3[x BST–（1-x）BFGO]（x = 0.00, 0.10, 0.20 and 0.25） multiferroic ceramics were prepared by the standard solid-state reaction technique. Structural characterization was performed by X-ray diffraction. All the samples showed rhombohedral distorted perovskite structure. Surface morphology of the ceramics was studied by the field emission scanning electron microscope（FESEM）. From the FESEM observation, the grain size was observed to be decreased with increasing BST content. Enhanced magnetic properties were observed in BFGO with the increase in BST content because of large lattice distortion. The complex initial permeability increased with the increasing of BST content. The study of dielectric properties showed that the dielectric constant increased, whereas dielectric loss decreased with increasing of BST content due to the reduction of oxygen vacancies. An analysis of the electric impedance and modulus with frequency was performed at different temperatures. Non-Debye-type relaxation processes occur in the compound which was confirmed from the nature of the Cole–Cole plot. The DC conductivity was found to increase with the rise in temperature which indicates the semiconducting behavior of the compound with characteristics of the negative temperature coefficient of resistance. The activation energy, responsible for the relaxation determined from the modulus spectra（0.246 eV）, was found to be almost same as the value obtained from the impedance study（0.240 eV）, indicating that charge carriers overcome the same energy barrier during relaxation. The frequency response of imaginary parts of electric impedance and modulus suggested that the relaxation in xB ST–（1-x）BFGO ceramics follows the same mechanism at various temperatures.

Impedance measurements of the extraction kicker system for the rapid cycling synchrotron of China Spallation Neutron Source

The fast extraction kicker system is one of the most important accelerator components and the main source of impedance in the Rapid Cycling Synchrotron of the China Spallation Neutron Source. It is necessary to understand the kicker impedance before its installation into the tunnel. Conventional and improved wire methods are employed in the impedance measurement. The experimental results for the kicker impedance are explained by comparison with simulation using CST PARTICLE STUDIO. The simulation and measurement results confirm that the window-frame ferrite geometry and the end plate are the important structures causing coupling impedance. It is proved in the measurements that the mismatching from the power form network to the kicker leads to a serious oscillation sideband of the longitudinal and vertical impedance and the oscillation can be reduced by ferrite absorbing material.