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  • Molecular Diversity Preservation International  (5)
  • Nomos Verlagsgesellschaft mbH & Co. KG
  • PANGAEA
  • 2020-2022  (5)
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Year
  • 1
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    Investigation of Particle Steering for Different Cylindrical Permanent Magnets in Magnetic Drug Targeting (2020)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2020-11-14
    Description: Magnetic Drug Targeting is a promising cancer treatment that offers the possibility of increasing therapeutic efficiency while reducing the patient’s side-effects. Thereby, the cancer-drug is bounded to magnetic nanoparticles, which are injected into a vessel and guided through the cardiovascular system into the tumor by an external magnetic field. However, a successful navigation depends on several multiphysical parameters including the properties of the nanoparticles, the flow characteristics of blood, and the gradient of the applied magnetic field. To investigate their impact, the propagation of particle packets within a 45∘ bifurcation vessel was modeled in COMSOL Multiphysics®. Therefore, magnets with varying radius-to-length ratios and magnetizations (radial and axial) were placed right before the bifurcation. Furthermore, different fluid velocities in addition to the influence of the gravitational force were evaluated. Overall, a strong dependency of the particle steering on the fluid velocity and the magnet’s radius-to-length ratio was observed. Moreover, a radial magnetization has a greater impact on the particle propagation, while the gravitation can be neglected for higher velocities. However, when a single permanent magnet is used, the results depict that it is a fine line between deflecting or trapping a particle at the vessel wall.
    Electronic ISSN: 2673-4591
    Topics: Technology
    Published by Molecular Diversity Preservation International
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  • 2
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    Performance Optimization of a Differential Method for Localization of Capsule Endoscopes (2020)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2020-11-14
    Description: Although capsule endoscopy is already used for diagnosis of the gastrointestinal tract, a method to precisely localize the capsules, important for accurate diagnosis, is lacking. Static magnetic localization is a promising solution for that purpose. In this paper, the simulation of a differential static magnetic localization system with dynamic geomagnetic compensation was optimized. First, a convergence-test for the position and orientation errors as a function of the dimension of the computational domain was conducted. Subsequently, the diameter-to-length ratio of a permanent magnet was varied and the corresponding position and orientation errors, as well as the mean magnetic flux density measured at the sensor positions, were compared. The results revealed that for a computational domain radius of 800 mm, the position and orientation errors converged to less than 0.1 mm and 0.1°, respectively. The position and orientation errors were also of that order, even with the smallest permanent magnet employed in the study. Furthermore, the mean magnetic flux density measured at the sensors of the proposed magnetic localization system would be detectable using state-of-the-art magnetometers. It is concluded that the differential localization method is also feasible for small permanent magnets, which is especially important considering the limited space within endoscopy capsules.
    Electronic ISSN: 2673-4591
    Topics: Technology
    Published by Molecular Diversity Preservation International
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  • 3
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    Common-Mode Noise Reduction in Noncontact Biopotential Acquisition Circuit Based on Imbalance Cancellation of Electrode-Body Impedance (2020)
    Molecular Diversity Preservation International
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    Publication Date: 2020-12-13
    Description: Biopotential sensing technology with electrodes has a great future in medical treatment and human—machine interface, whereas comfort and longevity are two significant problems during usage. Noncontact electrode is a promising alternative to achieve more comfortable and long term biopotential signal recordings than contact electrode. However, it could pick up a significantly higher level of common-mode (CM) noise, which is hardly solved with passive filtering. The impedance imbalance at the electrode-body interface is a limiting factor of this problem, which reduces the common mode rejection ratio (CMRR) of the amplifier. In this work, we firstly present two novel CM noise reduction circuit designs. The circuit designs are based on electrode-body impedance imbalance cancellation. We perform circuit analysis and circuit simulations to explain the principles of the two circuits, both of which showed effectiveness in CM noise rejection. Secondly, we proposed a practical approach to detect and monitor the electrode-body impedance imbalance change. Compared with the conventional approach, it has certain advantages in interference immunity, and good linearity for capacitance. Lastly, we show experimental evaluation results on one of the designs we proposed. The results indicated the validity and feasibility of the approach.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by Molecular Diversity Preservation International
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  • 4
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    Low-Frequency Magnetic Localization of Capsule Endoscopes with an Integrated Coil (2021)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2021-05-17
    Description: Wireless capsule endoscopy is a promising and less invasive alternative to conventional endoscopy. A patient swallows a small capsule with an integrated camera to capture a video of the gastrointestinal tract. For accurate diagnosis and therapy, the capsule position in terms of the travelled distance must be known for each video frame. However, to date, there is no reliable localization method for endoscopy capsules. In this paper, a novel magnetic localization method is proposed. A coil as a magnetic field source is integrated into a capsule and fed with a low-frequency alternating current to prevent static geomagnetic field interference. This alternating magnetic field is measured by twelve magnetic sensors arranged in rings around the abdomen. The coil and the capsule batteries were designed based on the geometry and power supply of a commercially available endoscopy capsule and simulated by COMSOL Multiphysics software. In this way, the coil position and orientation were determined with an accuracy below 1 mm and 1°, respectively. As an analytic model for the magnetic flux density of the coil in that setup, a modified dipole model was derived. It was used to show that the batteries help to increase the amplitude of the magnetic flux density. The model is valid when signals below 100 Hz are applied, and no eddy currents are generated within the batteries. It is concluded that the magnetic flux density generated by the developed coil would be measurable with state-of-the-art magnetic sensors.
    Electronic ISSN: 2673-4591
    Topics: Technology
    Published by Molecular Diversity Preservation International
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  • 5
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    Simulation-Based Resilience Quantification of an Indoor Ultrasound Localization System in the Presence of Disruptions (2021)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2021-09-22
    Description: Time difference of arrival (TDOA) based indoor ultrasound localization systems are prone to multiple disruptions and demand reliable, and resilient position accuracy during operation. In this challenging context, a missing link to evaluate the performance of such systems is a simulation approach to test their robustness in the presence of disruptions. This approach cannot only replace experiments in early phases of development but could also be used to study susceptibility, robustness, response, and recovery in case of disruptions. The paper presents a simulation framework for a TDOA-based indoor ultrasound localization system and ways to introduce different types of disruptions. This framework can be used to test the performance of TDOA-based localization algorithms in the presence of disruptions. Resilience quantification results are presented for representative disruptions. Based on these quantities, it is found that localization with arc-tangent cost function is approximately 30% more resilient than the linear cost function. The simulation approach is shown to apply to resilience engineering and can be used to increase the efficiency and quality of indoor localization methods.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by Molecular Diversity Preservation International
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