Effects of Time-Varying Magnetic Fields in the Frequency Range 1 kHz to 100 kHz upon the Human Body : Numerical Studies and Stimulation Experiment

In this work, the physiological effects of time-varying magnetic fields up to 100 kHz have been investigated, namely magnetic stimulation and body warming. Simulation studies were based on numerical calculations on sophisticated cell and body models. In addition, magnetic stimulation thresholds have been determined experimentally. The project was carried out within the scope of the development of Magnetic Particle Imaging, a new imaging technology for medical diagnostics

Doppler Encoded Excitation Patterning (DEEP) Microscopy

Traditional optical imaging systems rely on lenses and spatially-resolved detection to probe distinct locations on the object. We develop a novel computational approach to 2D and 3D imaging that instead measures the object\u27s spatial Fourier transform using a single-element detector and without requiring precision optics. This wide-field technique can be used to image biological and synthetic structures in fluoresced or scattered light using coherent or broadband illumination. It employs dynamic structured illumination, acousto-optics, RF electronics, and tomographic algorithms to circumvent several trade-offs in conventional imaging, such as the dependence of the optical transfer function on the imaging lenses and the coupling of resolution and depth of field. We use Fourier optics concepts to derive the dynamic optical transfer function, evaluate different Fourier sampling strategies, and investigate and compare tomographic algorithms for 2D and 3D image synthesis. We also develop conceptual and analytical models to describe imaging of fluorescent as well as amplitude and phase scattering objects, the effects of broadband and spatially-incoherent illumination, and nonlinear wide-field super-resolution imaging. We consider sources of noise, analyze and simulate SNR behavior for several types of noise and Fourier sampling strategies, and compare the sensitivity of the technique to conventional imaging. We describe several experimental proof-of-concept systems and present two-dimensional high-resolution tomographic image reconstructions in both scattered and fluoresced light demonstrating a thousandfold improvement in the depth of field compared to conventional lens-based microscopy. Finally, we explore approaches for high-speed Fourier sampling and propose several related sensing techniques, including wide-field fluorescence imaging in scattering media

Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers

Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method

Annual Report 2013 - Institute of Ion Beam Physics and Materials Research

The year 2013 was the third year of HZDR as a member of the Helmholtz Association (HGF), and we have made progress of integrating ourselves into this research environment of national Research centers. In particular, we were preparing for the evaluation in the framework of the so-called program oriented funding (POF), which will hopefully provide us with a stable funding for the next five years (2015 – 2019). In particular, last fall we have submitted a large proposal in collaboration with several other research centers. The actual evaluation will take place this spring. Most of our activities are assigned to the program “From Matter to Materials and Life” (within the research area “Matter”). A large fraction of this program is related to the operation of large-scale research infrastructures (or user facilities), one of which is our Ion Beam Center (IBC). The second large part of our research is labelled “in-house research”, reflecting the work driven through our researchers without external users, but still mostly utilizing our large-scale facilities such as the IBC, and, to a lesser extent, the free-electron laser. Our in-house research is performed in three so-called research themes, as depicted in the schematic below. What is missing there for simplicity is a small part of our activities in the program “Nuclear Waste Management and Safety” (within the research area “Energy”)

MATLAB

This excellent book represents the final part of three-volumes regarding MATLAB-based applications in almost every branch of science. The book consists of 19 excellent, insightful articles and the readers will find the results very useful to their work. In particular, the book consists of three parts, the first one is devoted to mathematical methods in the applied sciences by using MATLAB, the second is devoted to MATLAB applications of general interest and the third one discusses MATLAB for educational purposes. This collection of high quality articles, refers to a large range of professional fields and can be used for science as well as for various educational purposes

Magnetoencephalography—theory, instrumentation, and applications to noninvasive studies of the working human brain

Magnetoencephalography (MEG) is a noninvasive technique for investigating neuronal activity in the living human brain. The time resolution of the method is better than 1 ms and the spatial discrimination is, under favorable circumstances, 2-3 mm for sources in the cerebral cortex. In MEG studies, the weak 10 fT-1 pT magnetic fields produced by electric currents flowing in neurons are measured with multichannel SQUID (superconducting quantum interference device) gradiometers. The sites in the cerebral cortex that are activated by a stimulus can be found from the detected magnetic-field distribution, provided that appropriate assumptions about the source render the solution of the inverse problem unique. Many interesting properties of the working human brain can be studied, including spontaneous activity and signal processing following external stimuli. For clinical purposes, determination of the locations of epileptic foci is of interest. The authors begin with a general introduction and a short discussion of the neural basis of MEG. The mathematical theory of the method is then explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices. Finally, several MEG experiments performed in the authors' laboratory are described, covering studies of evoked responses and of spontaneous activity in both healthy and diseased brains. Many MEG studies by other groups are discussed briefly as well.Peer reviewe

Aerospace Applications of Magnetic Suspension Technology, part 2

In order to examine the state of technology of all areas of magnetic suspension with potential aerospace applications, and to review related recent developments in sensors and control approaches, superconducting technology, and design/implementation practices, a workshop was held at NASA-Langley. Areas of concern are pointing and isolation systems, microgravity and vibration isolation, bearing applications, wind tunnel model suspension systems, large gap magnetic suspension systems, controls, rotating machinery, science and applications of superconductivity, and sensors. Papers presented are included