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Integration of Stem Cell-Derived Neurons with Multi-Electrode Array
(2024) Simonsson, Isabella; Chalmers tekniska högskola / Institutionen för life sciences; Chalmers University of Technology / Department of Life Sciences; Asplund, Maria; Bengtsson, Niklas
The prevalence of serious mental illnesses (SMI) in the US adult population, in- cluding bipolar disorder (BP), major depressive disorder (MDD), and schizophrenia (SCZ), is estimated at 4-6%. While the creation of in vitro models from human induced pluripotent stem cells (hiPSCs) has transformed disease modeling in such illnesses, further research is needed to optimize these models. This project utilizes the human embryonic stem cell (hESC) line H1 to investigate the electrophysiological activity of stem cell-derived cortical neurons using Multi- Electrode Arrays (MEA). By integrating micro-electrodes into cell well-plates, neu- ral activity can be non-destructively measured over several weeks with MEA. The objective is to optimize the integration of stem cell-derived neurons with MEA for monitoring electrophysiological activity, evaluating different cell densities, coatings, and culturing mediums. Comprising a pilot study followed by a more extensive investigation, this project compares metrics such as activity and electrode coverage across various culturing conditions to identify optimal parameters. The most promising condition entails a cell density of 50k cells per well, coated with both Poly-L-Ornithine (PLO) and Bi- olaminin 521 (LN521), and cultured in either Neural Maintenance Medium (NMM) or BrainPhys (BP).
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Vessel-on-a-Chip Development to Understand Systemically Administered NanoparticlesVessel-on-a-Chip Development to Understand Systemically Administered Nanoparticles
(2024) Jia, Fan; Chalmers tekniska högskola / Institutionen för life sciences; Chalmers University of Technology / Department of Life Sciences; Stubelius, Alexandra; Svensson, Elin
Nanomedicine holds great promise for treating complex diseases, particularly due to its unique ability to sustain and target drug delivery. However, the validation method has been a great challenge to the development of nano-based therapeutics. The main reason is the unpredictable delivery dosage and lack of adequate preclinical trial methods that replicate the human biological environment for testing nanomedicine. This project introduced organ-on-a-chip (OOC) method to mimic the human vascular environment in vitro for studying the transportation of nanoparticles in human vessels. The goal was to use commercially available resources to increase the generalization and ease of adaptability for other labs working within the field of nanomedicine. The build-up of this vessel-on-a-chip (VoC) was successfully achieved using a microfluidic chip from Ibidi along with a microfluidic set-up to stimulate the human umbilical vein endothelial cells (HUVEC) seeded in the chip. The cells formed an oriented endothelial cell (EC) monolayer mimicking the endothelium of a capillary under a 24-hour flow of 10dyn/cm2. This monolayer acted as a barrier preventing NPs from extravasating into the tissue, which is an important aspect of nanoparticle delivery. In addition, a computational fluidic dynamic (CFD) simulation approach was conducted to further enhance the predictability of NP transportation. The microfluidic simulation helped to explain unexpected phenomena during the flow experiment.Although the blood flow simulation had some limitations, it could provide useful insights when evaluating a potential uptake amount of NPs when administered systemically. This integrated study of combining VOC with CFD simulation enhances our understanding of NP behavior in human vessels but requires further optimization to be fully operational.
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Wide Area Synchronization Functionality
(2024) Mohamed, Abdin; Chalmers tekniska högskola / Institutionen för elektroteknik; Chen, Peiyuan; Karlsson, Daniel
Abstract Large interconnected power systems are constantly exposed to unpredictable disturbances that may often lead to system splits. This creates two or more synchronous areas where some end up with generation surplus and the others with generation deficit, and corresponding frequency deviations, which in most cases results in load shedding. Afterwards when the subsystems stabilize, the tricky part comes when its time for resynchronization since the systems are large compared to a small area. This thesis presents a development and testing of a phasor measurement unit (PMU)- based method with the aid of Wide Area Measurement Systems (WAMS) which introduces an immediate solution for the issue of stabilization and synchronization of subsystems. PMU sensors are fast, real time-stamped accurate devices linked to the Global Positioning System (GPS) that measure synchrophasors at various points on the grid, which would help transmission system operators (TSOs) to react and counteract any event or disturbance that might threaten the system. The research employs PSS/E software to perform static and dynamic load flow analysis on the Nordic power system when a disturbance occurred in the system that led into splitting to two synchronous areas. During the resynchronization process, two methods were evaluated: the conventional method (sequential reconnection) characterized by limited data gathering and communication delays between TSOs, and the developed method (simultaneous reconnection) that leverages the use of PMUs for reconnection of the lines, hence the system’s response was observed. Synchronization data that include frequency, voltage and phase angle differences from the subsystems, which were output, analyzed and compared for both methods. The results demonstrate that the simultaneous reconnection utilizing PMU sensors which provided real-time data that enabled TSOs to identify the lines that were tripped due to the disturbance created hence discovering the disturbance location and mitigate around the area of the split, as rapid as possible. In addition, the system downtime and the risk of further instability is reduced. This method added more to the understanding of the sequential reconnection method which is currently used for the resynchronization of subsystems while showcasing the benefits the simultaneous method when it comes to reconnection. Most likely in the near future the simultaneous method will replace the sequential reconnection method when more renewable energy sources are integrated.
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Fermi Surfaces of Holographic Metals
(2024) ISMAILOV, ELI; Chalmers tekniska högskola / Institutionen för fysik; Chalmers University of Technology / Department of Physics; Gran, Ulf; Nilsson, Eric
One of the most challenging endeavours in theoretical condensed matter physics is solving models of strongly correlated metals. In these systems, the standard techniques from Fermi liquid theory have limited applicability, necessitating new descriptions. One particularly promising approach is known as holographic duality, which conjectures a relation between the seemingly unapproachable physics of strongly coupled quantum field theories and classical gravitational theories in one higher dimension. While successful in many regards, the usual holographic approach for metals fails to incorporate a satisfactory description of a Fermi surface, an indisputably important ingredient for any theory describing a metal. Specifically, any theory of a metal ought to have a Fermi surface that satisfies Luttinger’s theorem. In this thesis, we introduce a holographic model that exhibits the necessary behaviour of metal. Diverging from the typical holographic treatment where all scales are described, we instead assume the dual theory to be an infrared effective field theory. We explore the behaviour of the theory across various temperatures by numerically solving the differential equations of motion for the gravity theory. Motivated by the numerical predictions, we suggest a UV cutoff scale for the theory. We discuss some potential limitations and plausible modifications of the model.
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Thermal Management of Electric Vehicle Rapid Charging
(2024) Barani, Amirhossein; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Vdovin, Alexey; Jahnen, Tim
One of the main barriers to rapid charging of electric vehicles is the thermal management of batteries and charging equipment. Current charging patterns are designed to maintain battery health and safety while avoiding thermal events. Additionally, protection systems monitor the temperature of charging components and, if it exceeds safe limits, reduce power intake to mitigate risks. This increases charging time and impacts the reliability of rapid charging systems. An efficient thermal management system plays a key role in increasing charging stability and enabling faster charging at higher capacities. This study investigates the thermal management of charging cables and power modules in a Megawatt Charging System (MCS) suitable for heavy-duty vehicles. The research is divided into two parts. First, 3D CFD simulations are conducted for three liquid-cooled cable structures to compare their performance and determine their energy loss and cooling demand. Based on these results, in the second part, four cooling systems (heatsink, heatsink+PCM, liquid cooling, and immersion coolng) are designed for the power modules, and their performance is studied through 1D simulations. The findings provide a holistic view of the capabilities of various thermal management strategies and determine their efficiency in various scenarios. Considering the oil-cooled charging cable model and the liquid cooling system as the reference, the results demonstrate that charging a heavy-duty EV with a 1 MW MCS under a constant current-constant voltage (CC-CV) charging method for 45 minutes transfers 370 kWh of energy to the battery. The total system efficiency, including power modules and cables, is 97.3%. Of the input energy, 9.12 kWh ( 2.4%) is lost in the power modules, 0.41 kWh ( 0.1%) in the charging cable and its cooling system, and 0.34 kWh ( 0.1%) in the power module cooling system.