Article
Refine
Year of publication
- 2019 (121) (remove)
Institute
- Fachbereich Medizintechnik und Technomathematik (52)
- IfB - Institut für Bioengineering (27)
- INB - Institut für Nano- und Biotechnologien (20)
- Fachbereich Luft- und Raumfahrttechnik (12)
- Fachbereich Energietechnik (11)
- Fachbereich Wirtschaftswissenschaften (11)
- Fachbereich Elektrotechnik und Informationstechnik (9)
- Fachbereich Maschinenbau und Mechatronik (8)
- Fachbereich Bauingenieurwesen (7)
- Fachbereich Chemie und Biotechnologie (7)
Document Type
- Article (121) (remove)
Keywords
- Achilles tendon (1)
- Arbeit 4.0 (1)
- Architectural gear ratio (1)
- Assistive technology (1)
- Automatic control (1)
- Chatbots (1)
- Datenschutz (1)
- Datenschutzgrundverordnung (1)
- Digitalisierung (1)
- Emilia-Romagna earthquake (1)
Is part of the Bibliography
- no (121)
The movement of magnetic beads due to a magnetic field gradient is of great interest in different application fields. In this report we present a technique based on a magnetic tweezers setup to measure the velocity factor of magnetically actuated individual superparamagnetic beads in a fluidic environment. Several beads can be tracked simultaneously in order to gain and improve statistics. Furthermore we show our results for different beads with hydrodynamic diameters between 200 and 1000 nm from diverse manufacturers. These measurement data can, for example, be used to determine design parameters for a magnetic separation system, like maximum flow rate and minimum separation time, or to select suitable beads for fixed experimental requirements.
In modern bioanalytical methods, it is often desired to detect several targets in one sample within one measurement. Immunological methods including those that use superparamagnetic beads are an important group of techniques for these applications. The goal of this work is to investigate the feasibility of simultaneously detecting different superparamagnetic beads acting as markers using the magnetic frequency mixing technique. The frequency of the magnetic excitation field is scanned while the lower driving frequency is kept constant. Due to the particles’ nonlinear magnetization, mixing frequencies are generated. To record their amplitude and phase information, a direct digitization of the pickup-coil’s signal with subsequent Fast Fourier Transformation is performed. By synchronizing both magnetic beads using frequency scanning in magnetic frequency mixing technique magnetic fields, a stable phase information is gained. In this research, it is shown that the amplitude of the dominant mixing component is proportional to the amount of superparamagnetic beads inside a sample. Additionally, it is shown that the phase does not show this behaviour. Excitation frequency scans of different bead types were performed, showing different phases, without correlation to their diverse amplitudes. Two commercially available beads were selected and a determination of their amount in a mixture is performed as a demonstration for multiplex measurements.
The paper deals with an asymptotic relative efficiency concept for confidence regions of multidimensional parameters that is based on the expected volumes of the confidence regions. Under standard conditions the asymptotic relative efficiencies of confidence regions are seen to be certain powers of the ratio of the limits of the expected volumes. These limits are explicitly derived for confidence regions associated with certain plugin estimators, likelihood ratio tests and Wald tests. Under regularity conditions, the asymptotic relative efficiency of each of these procedures with respect to each one of its competitors is equal to 1. The results are applied to multivariate normal distributions and multinomial distributions in a fairly general setting.