Search Results

1 - 8 of 8 items :

  • "magnetic susceptibility" x
  • Control Engineering, Metrology and Testing x
Clear All
The Magnetoplasmic Measurements of the Carrier Density in Many-Component Solid State Plasma

The Magnetoplasmic Measurements of the Carrier Density in Many-Component Solid State Plasma

Many semiconductor materials manufactured by help of nanotechnology have charge carriers of different type and mobility. Already existing carrier density and mobility measurement methods are not accurate enough for the case of several carrier components. The use of magnetoplasmic waves provides a simple and the most precise way to determine the density and mobility of each type of the carriers (electrons and/or holes).

Magnetoplasmic waves may be excited in semiconductors when the strong magnetic field H is applied. The semiconductor sample becomes partially transparent under these conditions. In the case of magnetoplasmic resonance within each of the carrier groups, the transparency coefficient has a maximum. For fixed values H and excitation frequency ω the density and mobility of every carrier type can be found.

Dispersion relation for two types of charge carriers is obtained and resonance curves are calculated.

Open access
Circular Samples as Objects for Magnetic Resonance Imaging - Mathematical Simulation, Experimental Results

Abstract

Circular samples are the frequent objects of "in-vitro" investigation using imaging method based on magnetic resonance principles. The goal of our investigation is imaging of thin planar layers without using the slide selection procedure, thus only 2D imaging or imaging of selected layers of samples in circular vessels, eppendorf tubes,.. compulsorily using procedure "slide selection". In spite of that the standard imaging methods was used, some specificity arise when mathematical modeling of these procedure is introduced. In the paper several mathematical models were presented that were compared with real experimental results. Circular magnetic samples were placed into the homogenous magnetic field of a low field imager based on nuclear magnetic resonance. For experimental verification an MRI 0.178 Tesla ESAOTE Opera imager was used.

Open access
Positioner and the Procedure for Measuring Spatial Characteristics

Abstract

The present work focuses on the solution of management of measuring spatial characteristics of security detectors using a positioner, a precision manipulator. It deals with program management software in LabView. Graphical programming with subroutines, which are described as virtual instruments, is used. There are published results of measurements of the spatial characteristics of the PIR detector, where it is preferably used as the measuring station.

Open access
MRI-Based Visualization of the Relaxation Times of Early Somatic Embryos

Abstract

The large set of scientific activities supported by MRI includes, among others, the research of water and mineral compounds transported within a plant, the investigation of cellular processes, and the examination of the growth and development of plants. MRI is a method of major importance for the measurement of early somatic embryos (ESE) during cultivation, and in this respect it offers several significant benefits discussed within this paper. We present the following procedures: non-destructive measurement of the volume and content of water during cultivation; exact three-dimensional differentiation between the ESEs and the medium; investigation of the influence of ions and the change of relaxation times during cultivation; and multiparametric segmentation of MR images to differentiate between embryogenic and non-embryogenic cells. An interesting technique consists in two-parameter imaging of the relaxation times of the callus; this method is characterized by tissue changes during cultivation at a microscopic level, which can be monitored non-destructively.

Open access
Magnetic Resonance Imaging of Surgical Implants Made from Weak Magnetic Materials

), 3293-3300. [13] Schenck, J.F. (1996). The role of magnetic susceptibility in magnetic resonance imaging: MRI magnetic compatibility of the first and second kinds. Medical Physics , 23 (6), 815-851. [14] Shellock, F.G. (2002). Biomedical implants and devices: Assessment of magnetic field interactions with a 3.0-Tesla MR system. Journal of Magnetic Resonance Imaging , 16, 721-732.

Open access
Measurement and Imaging of Planar Electromagnetic Phantoms Based on NMR Imaging Methods

. IEEE Trans. on Magnetics , 40, 2188-2190. Frollo, I., Andris, P., Přibil, J., Juráš, V. (2007). Indirect susceptibility mapping of thin-layer samples using nuclear magnetic resonance imaging. IEEE Trans. on Magnetics , 43 (8), 3363-3367. Bhagwandien, R., Moerland, M., Bakker, C., Beersma, R., Lagendijk, J. (1992). Numerical analysis of the magnetic field for arbitrary magnetic susceptibility distributions in 2D. Magnetic Resonance Imaging , 10 (2), 299-313. Willcott, M. R., Mee, G. L

Open access
Diffusion MRI: mitigation of magnetic field inhomogeneities

the analysis of diffusion MRI data. Biomedicine [19] Valkovic, L., Windischberger, C. (2010). Method for geometric distortion correction in fMRI based on three echo planar phase images. Review [20] Pribil, J., Horacek, J., Horak, P. (2011). Two methods of mechanical noise reduction of recorded speech during phonation in an MRI device. Science Review [21] Marcon, P., Bartusek, K., Burdkova, M., Dokoupil, Z. (2011). Magnetic susceptibility measurement using 2D magnetic resonance imaging. and Technology

Open access
Time-Efficient Perfusion Imaging Using DCE- and DSC-MRI

in Medicine , 30(6), 764–768. [36] Pedersen, M., Klarhöfer, M., Christensen, S. r., Ouallet, J.-C., Østergaard, L., Dousset, V., Moonen, C. (2004). Quantitative cerebral perfusion using the PRESTO acquisition scheme. Journal of Magnetic Resonance Imaging , 20(6), 930–940. [37] Boxerman, J.L., Hamberg, L.M., Rosen, B.R., Weisskoff, R.M. (1995). MR contrast due to intravascular magnetic susceptibility perturbations. Magnetic Resonance in Medicine , 34(4), 555–566. [38] Kjølby, B.F., Østergaard, L., Kiselev, V.G. (2006). Theoretical model of

Open access