The role of the nucleus for cell mechanics: an elastic phase field approach

The nucleus of eukaryotic cells typically makes up around 30 % of the cell volume and tends to be up to ten times stiffer than the surrounding cytoplasm. Therefore it is an important element for cell mechanics, but a quantitative understanding of its mechanical role is largely missing. Here we demonstrate that elastic phase fields can be used to describe dynamical cell processes in adhesive or confining environments in which the nucleus plays an important role. We first introduce and verify our computational method and then study several applications of large relevance. For cells on adhesive patterns, we find that nuclear stress is shielded by the adhesive pattern. For cell compression between two parallel plates, we obtain force-compression curves that allow us to extract an effective modulus for the cell-nucleus composite. For micropipette aspiration, the effect of the nucleus on the effective modulus is found to be much weaker, highlighting the complicated interplay between extracellular geometry and cell mechanics that is captured by our approach.Comment: 13 pages, 6 figure

Boosting resonant switched-capacitor voltage tripler

This elaboration presents the concept of a unidirectional DC–DC switchedcapacitor converter operating as a voltage tripler. The system consists of two resonant cells with switched capacitors and chokes. This proposed converter topology achieves low voltages on semiconductor switches (diodes and transistors) compared to the classic SC series-parallel converter or the boost topology. The output voltage on the capacitors is reduced in the proposed converter because it is divided into two series-connected capacitors with asymmetric distribution. The presented results describe the analytical description of the system operation and the analytical equation for semiconductor currents. A simulation and experimental results have been performed. The system efficiency and three voltage gain values were measured in the experimental setup. The efficiency measured was also compared with the analytical determination curve for loss analysis and further converter optimization

An Analysis of a Transformerless Dual Active Half-Bridge Converter

This paper proposes a transformerless dual half-bridge converter (TLDAHB). By eliminating the transformer and harnessing the possibility of using a low inductor value, it is possible to minimise the size of the converter. A phase-shift pulse width modulation will result in a wide controlled voltage gain of the converter and operation as buck and boost. The theoretical topology analysis, simulation, and experimental results are presented. Theoretical analysis consists of analysis of power transfer and design. In case of experimental research, particular attention was paid to power transfer and efficiency analysis. Near zero switching transient of voltage in the half-bridge topology results with high efficiency

Thermal and Electric Parameter Analysis of DC–DC Module Based on Resonant Switched Capacitor Converter

This elaboration presents the concept of the design, parameters, experimental investigation, and thermal numerical model solved using the finite element method of a high-power-density DC–DC converter. The analyzed unit can be utilized as a stand-alone converter or as a module for a scalable high-voltage gain system. The converter has a decreased bill of materials since it does not use typical chokes and heatsinks. It is based on switched capacitor circuits supported by a resonant choke which protects against inrush currents. A printed circuit board is utilized not only for the resonant inductance design but also for cooling transistor and diode devices. The paper demonstrates the design concept and the achieved parameters. Experimental results show heat distribution on the printed circuit board and components in a steady state and dynamical states as well. The converter parameters and their efficiency are measured as well. The convergence of experimental results and heating simulations is demonstrated. The numerical model is used for the investigation of design cases. The printed circuit board size, thermal via pattern, and heating process during the overload of the converter are investigated

Thermal and Electric Parameter Analysis of DC–DC Module Based on Resonant Switched Capacitor Converter

This elaboration presents the concept of the design, parameters, experimental investigation, and thermal numerical model solved using the finite element method of a high-power-density DC–DC converter. The analyzed unit can be utilized as a stand-alone converter or as a module for a scalable high-voltage gain system. The converter has a decreased bill of materials since it does not use typical chokes and heatsinks. It is based on switched capacitor circuits supported by a resonant choke which protects against inrush currents. A printed circuit board is utilized not only for the resonant inductance design but also for cooling transistor and diode devices. The paper demonstrates the design concept and the achieved parameters. Experimental results show heat distribution on the printed circuit board and components in a steady state and dynamical states as well. The converter parameters and their efficiency are measured as well. The convergence of experimental results and heating simulations is demonstrated. The numerical model is used for the investigation of design cases. The printed circuit board size, thermal via pattern, and heating process during the overload of the converter are investigated

Nanostructure of clustered DNA damage in leukocytes after in-solution irradiation with the alpha emitter Ra-223

Background: Cancer patients are increasingly treated with alpha-particle-emitting radiopharmaceuticals. At the subcellular level, alpha particles induce densely spaced ionizations and molecular damage. Induction of DNA lesions, especially clustered DNA double-strand breaks (DSBs), threatens a cell's survival. Currently, it is under debate to what extent the spatial topology of the damaged chromatin regions and the repair protein arrangements are contributing. Methods: Super-resolution light microscopy (SMLM) in combination with cluster analysis of single molecule signal-point density regions of DSB repair markers was applied to investigate the nano-structure of DNA damage foci tracks of Ra-223 in-solution irradiated leukocytes. Results: Alpha-damaged chromatin tracks were efficiently outlined by γ-H2AX that formed large (super) foci composed of numerous 60–80 nm-sized nano-foci. Alpha damage tracks contained 60–70% of all γ-H2AX point signals in a nucleus, while less than 30% of 53BP1, MRE11 or p-ATM signals were located inside γ-H2AX damage tracks. MRE11 and p-ATM protein fluorescent tags formed focal nano-clusters of about 20 nm peak size. There were, on average, 12 (±9) MRE11 nanoclusters in a typical γ-H2AX-marked alpha track, suggesting a minimal number of MRE11-processed DSBs per track. Our SMLM data suggest regularly arranged nano-structures during DNA repair in the damaged chromatin domain