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- Elektrotechnik und angewandte Naturwissenschaften (59) (entfernen)
Nanofluids, defined as fluids containing suspended solid nanoparticles, are potential systems for utilization in biomedical applications. Magnetic Particle Imaging (MPI) uses superparamagnetic nanofluids, e.g. a colloidal suspension of iron oxide particles. In this work a new biocompatible nanofluid based on pure and stable ferromagnetic carbon is investigated. Although this material has a relatively small value of coercive magnetic field, it does exhibit a true ferromagnetic behavior up to 300 K. We present results obtained from numerical investigations performed to calculate the impact of a ferromagnetic magnetization to the MPI signal chain. Moreover, by modeling ferromagnetic magnetization we prove here the general suitability of ferromagnetic materials for MPI. Due to the low saturation magnetization, however, MPI for ferromagnetic carbon will be possible only in the near future when realistic concentrations of the nanofluid ferromagnetic carbon will be experimentally obtainable.
Many fluids transported by pipelines are in some sense hazardous. It is therefore often necessary to install leak detection (and locating) systems (LDS), especially due to legal regulations like the "Code for Federal Regulations (CFR) Title 49 Part 195", API 1130 2nd Ed., both for the USA, or the "Technische Regeln für Fernleitungen" (TRFL) (Technical Rules for Pipelines) in Germany. This paper gives a survey of methodologies, methods and techniques for leak detection and locating. The survey starts with some remarks concerning (legal) regulations both for the USA and for Germany. Some few words about externally based systems (due to API 1130 2nd Ed.) follow next. A significant part of the paper deals with internally based systems (also due to API 1130 2nd Ed.) like balancing systems (line balance, volume balance, compensated mass balance etc.), Real Time Transient Model LDS (RTTM-LDS), pressure/flow monitoring and statistical analysis LDS. Different methods for leak locating (gradient intersection method, wave propagation analysis etc.) will also be shown. The presentation of an Extended RTTM approach (E-RTTM) combining advantages of conventional RTTM LDS and statistical analysis follows next, together with the demonstration of applicability by means of two examples, a liquid multi-batch pipeline, and a gas pipeline. Sketching future work and the conclusion conclude the survey.
We report on investigations that illustrate the interaction between the specific immune system and a young avascular tumor growing due to a diffusive nutrient supply. We formulate a hybrid cellular automata-partial differential equation (CA-PDE) model which includes cell cycle dynamics and allows for tracking the spatial and temporal evolution of this elaborate biological system. We present results of two dimensional numerical simulations that, specifically in this work, include special cases of the spherical and papillary tumor growth, the infiltration of immune system cells into the tumor and the escape of tumor cells from the regime of the immune cells.
We report on the suitability of two different ranges of Hounsfield units (HU) in computed tomography (CT) for the quantification of metallic components of active implantable medical devices (AIMD). The conventional Hounsfield units (CHU) range, which is traditionally used in radiology, is well suited for tissue but suspected inappropriate for metallic materials. Precise HU values are notably beneficial in radiotherapy (RT) for accurate dose calculations, thus for the safety of patient carrying implants. Some of today’s CT machines offers an extended Hounsfield units (EHU) range. This study presents CT acquisitions of a water phantom containing various metallic discs and an implantable-cardioverter defibrillator (IPG). We show that the comparison of HU values at EHU and CHU ranges clearly reveals the superiority and accuracy of EHU. Some geometrical discrepancies perpendicular to slices are observed. At EHU metal artifact reduction algorithms (MAR) underestimates HU values rendering MAR potentially inappropriate for RT.