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Protoplasts under stress:Investigating the effect of compression on protoplasts using microfluidics
No full textProtoplasts are plant cells which have had their cell walls enzymatically removed. They can be isolated from almost any plant tissue of many different plant species. The key feature of protoplasts is that they can be induced to regenerate from a single cell back into a full plant. The regeneration of a protoplast into a specific tissue type or a whole plant is a complex, time and labor-consuming task with a yield that is not easy to predict, as all the factors affecting the regeneration efficiency, both internal and external, are not yet fully understood. The complexity of the regeneration process makes it difficult to investigate the sub-processes happening therein. There are phenomena that still bear exploration even in the early, single-cell stage of regeneration. In this thesis, we investigated whether the application of mechanical compression on a single protoplast in a finely controlled microfluidic environment can affect their divisions and cell wall regeneration. Microfluidics served here as an engineering tool, that enabled us to reproducibly apply stimuli to cultured cells and closely observe the result. In this thesis, microfluidic platforms were used to investigate the initial divisions of freshly isolated protoplasts of Nicotiana tabacum, a widely used model plant species. Uniquely, our devices allowed us to affect these protoplasts with mechanical compression without also introducing other known factors of influence like osmotic stress. Our microfluidic device was designed to be compatible with high-content imaging platforms, allowing us to generate large time-resolved image datasets of cell behavior. Due to the large quantities of data generated on this platform and the sometimes subtle effects that compression has on the regeneration process, we recognized a strong need for automated tools for data analysis. Additionally, such a rich dataset could serve as the input for a prediction model that would make it possible to predict the outcome of the regeneration of a single protoplast based on its initial image. Such a model would be of great value both for fundamental biology, as it can help identify specific features crucial for the regeneration success, and the crop industry, as then it can significantly improve the efficiency of the regeneration process
Nanofabrication of 3D Photonic Band Gap Crystals from Silicon to Control the Emission of Light
No full textEffect of load and twist on filament packing in three-strand aramid fibre ropes: a micro-CT study
No full textThis study investigates how varying rope and strand twists influence the filament packing fraction in three-strand Aramid fibre ropes. Micro-computed tomography (micro-CT) scanning was used to visualize and quantify filament arrangements under different twist configurations and loads. High-resolution CT-scan image segmentation enabled the calculation of local filament packing fractions. Results indicate that twist parameters strongly affect how tightlyfilaments pack inside strands, particularly when a tensile load is applied. Higher twist levels often lead to a more compact internal structure, whereas lower twist levels introduce voids and an uneven arrangement. Under tensile loading, additional compaction is observed, especially at strand-to-strand interfaces. The findings help in understanding how twist geometry and applied tensile load redistribute filaments in a three-strand configuration, providing insights intoload sharing, potential filament slip, and internal damage – all critical factors in assessing rope performance and service life
Planning Under Uncertainties with Closed-Loop Sensitivity:Recent Results and Perspectives
No full textThis paper presents a comprehensive summary of recent advancements in motion planning under parametric uncertainties, focusing on the application of closed-loop state sensitivity. This concept provides a framework for quantifying how deviations in model parameters affect the behavior of a system in closed-loop, facilitating the generation of robust trajectories. Various methods have been proposed to improve the resilience of robotic systems to model inaccuracies. However, these approaches often face challenges such as computational complexity and limitations in real-time applications. This paper synthesizes key results from several recent works, highlighting the development of techniques that optimize trajectory robustness while reducing computational overhead. Additionally, we outline the practical applications of these methods, discussing their validation through simulations and experiments on robotic systems subject to non-negligible uncertainties in their models.</p
A Silicon-Based Combined Hot-Element and Calorimetric Anemometer
Get PDFA micro-fabricated silicon-based anemometer has been improved by employing a differential calorimetric measurement technique, while additional sensing information is extracted from the constant temperature heater. This combination improves the measurement range, as established experimentally and supported by finite element simulations. The straight-forward three mask fabrication process is also presented. The use of a lock-in amplifier to read out the sensing elements also provides additional information on the wind direction contained in the phase shift. With this information and theoretical basis, the combined anemometer leads to an increased measurement range and an improved <1% full-scale precision.</p
Measurement and Modeling of Initial Quench Development in Nb<sub>3</sub>Sn Accelerator Magnets
Get PDFAccelerator magnets are equipped with voltage taps and, on the test bench, with so-called quench antenna's to monitor the transient effects occurring during a magnet quench. Proper identification and localization of a quench origin is vital for understanding performance issues in Nb3Sn accelerator magnets. In this paper, we describe the physical phenomena that occur during the first few milliseconds of a developing quench and how they affect the signals as intercepted with the diagnostic tools. A better understanding of these phenomena allows for better resolution on determination of the quench start location. Measurements from Nb3Sn accelerator magnets are compared with a 3D thermal-electric PEEC-FEM model of a Rutherford cable. The voltage measured over the cable shows an accelerating build-up attributed to the transverse quench propagation in the cable cross-section, which is dominated by inductive effects that results in an avalanche of quenching strands. A slow-down in the voltage build-up then indicates the point at which all strands in the cable cross-section have quenched. This phase of the quench involves a significant current redistribution that creates a magnetic dipole moment picked up by a quench antenna. The harmonic quench antenna used in this work is used to reconstruct the location, magnitude, and direction of this dipole moment, which strongly depends on the start location of the quench in the cable cross-section, on the inter-strand contact resistances and on the magneto-resistance of the copper. It is shown how the quench start location in the cable cross-section can be determined from the time integral of the reconstructed dipole moment.</p
Mechanical and electromagnetic characteristics of MgB<sub>2</sub> wires & Cable-in-Conduit Conductors for fusion magnet application
Get PDFA study on a 4-stage sub-size MgB 2 Cable-in-Conduit Conductor (CICC), tested at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), revealed a 20% degradation in critical current at 4.2 K compared to single-strand data. To address this issue, the mechanical properties of MgB 2 wires from Hyper Tech and WST were investigated, and two sub-size CICCs were manufactured using a “close-to-1-ratio” Twente design with smaller diameter wires. These cables demonstrated no significant degradation in critical current after cabling and compaction, nor after electromagnetic load cycling. The results indicate that the close-to-1-ratio cable design is optimal for brittle superconducting materials such as MgB 2, Nb3Sn, and BSCCO, as it minimizes mechanical stress and preserves superconducting properties. This design shows significant potential for the application of MgB 2 in next-generation fusion reactors, particularly in Poloidal Field (PF) coils, Correction Coils (CC), and feeders.</p
A CRISP-DM-based methodology for assessing agent-based simulation models using process mining
Get PDFAgent-based simulation (ABS) models are powerful tools for analyzing complex systems. However, understanding and validating ABS models can be challenging. Data-driven techniques, such as process mining, offer promising capabilities for addressing these challenges. Process mining enables the discovery, monitoring, and enhancement of processes by extracting insights from event logs. However, applying process mining to ABS-generated logs and interpreting the results is not trivial. Despite its potential, limited methodological guidance exists for using process mining in ABS evaluation. This paper proposes a methodology, grounded in the CRoss-Industry Standard Process for Data Mining (CRISP-DM), to assess ABS models via process mining. By integrating process mining techniques into the phases of CRISP-DM, we support the analysis of ABS behaviors and their underlying processes. We demonstrate our methodology using Schelling’s segregation model. Our results indicate that our proposed methodology effectively evaluates ABS models using event logs, enhancing model validity and supporting more informed decision-making.</p
