Background: The voltage gated K⁺ channel Kv1.5 participates in the repolarization of a wide variety of cell types. Kv1.5 is downregulated during hypoxia, which is known to stimulate the energy-sensing AMP-activated serine/threonine protein kinase (AMPK). AMPK is a powerful regulator of nutrient transport and metabolism. Moreover, AMPK is known to downregulate several ion channels, an effect at least in part due to stimulation of the ubiquitin ligase Nedd4- 2. The present study explored whether AMPK regulates Kv1.5. Methods: cRNA encoding Kv1.5 was injected into Xenopus oocytes with and without additional injection of wild-type AMPK (α1 β 1γ1), of constitutively active ^γR70QAMPK (α1 β 1γ1(R70Q)), of inactive mutant ^αK45RAMPK (α1(K45R)β1γ1), or of Nedd4-2. Kv1.5 activity was determined by two-electrode voltage-clamp. Moreover, Kv1.5 protein abundance in the cell membrane was determined by chemiluminescence and immunostaining with subsequent confocal microscopy. Results: Coexpression of wild-type AMPK^WT and constitutively active AMPK^γR70Q, but not of inactive AMPK^αK45R significantly reduced Kv1.5-mediated currents. Coexpression of constitutively active AMPKγR70Q further reduced Kv1.5 K⁺ channel protein abundance in the cell membrane. Co-expression of Nedd4-2 similarly downregulated Kv1.5-mediated currents. Conclusion: AMPK is a potent regulator of Kv1.5. AMPK inhibits Kv1.5 presumably in part by activation of Nedd4- 2 with subsequent clearance of channel protein from the cell membrane.

This study presents a detailed numerical analysis of substrate boards made from various materials (FR-4, Si cladding, and Cu cladding) with nine electronic components mounted on them. Each component is subjected to different heat fluxes, and the analysis covers both natural convection (NC) and forced convection (FC) modes of heat transfer at air velocities of 4m/s and 6m/s. The findings reveal that at an air velocity of 6m/s, using a copper cladding board significantly lowers the temperatures of the electronic components by 340C to 540C compared to FR-4 and Si cladding boards. Additionally, the copper cladding reduces the required air-cooling velocity by 2m/s and achieves a temperature reduction for the IC chips ranging from 3.500C to 13.120C. It is recommended to use an air velocity of 4m/s with copper cladding to minimize fan power consumption while maintaining component temperatures below 1250C. These results provide crucial insights for thermal design engineers, aiding in the selection of appropriate substrate boards for effective thermal management of electronic components. The study emphasizes the benefits of copper cladding in distributing heat more uniformly, reducing energy consumption, and maintaining optimal operating temperatures. Furthermore, it suggests that placing high heat-dissipating components at inlet or outlet points can minimize thermal interactions and overall configuration temperatures. The research offers valuable guidance to the heat transfer community, particularly electronic thermal designers, by highlighting the importance of substrate material choice and component placement in enhancing the reliability and lifespan of integrated circuits (ICs). The comprehensive analysis and recommendations serve as a vital resource for optimizing thermal control strategies in electronic devices, ultimately contributing to improved performance and durability.

Modern smartphones are used for a wide range of demanding tasks, such as gaming, high-resolution photography, and internet browsing, which significantly increases their power consumption. This excessive power use leads to higher heat generation within the device, typically between 2 and 6 watts. To manage this heat and maintain optimal performance, smartphones employ various cooling techniques. A new mobile cooling method could use innovative approaches like advanced phase change materials, liquid cooling systems, or emerging technologies such as thermoelectric and microfluidic cooling. This paper proposes a new cooling method using phase change materials. This approach leverages the material's ability to absorb heat by transitioning from a solid to a liquid state and vicecersa. This helps keep the device's temperature below 45 degrees Celsius. In mid-range smartphones, cooling methods such as natural convection, indirect heat-pipe cooling, and forced convection are commonly used, but these methods often fail under high-power usage conditions.

This paper presents an implicit transient numerical formulation for a novel passive thermal management system using minichannels to cool heterogeneous IC chips on a substrate board. The proposed design incorporates phase change materials (PCM) within minichannels situated around the periphery of the IC chips. By direct conduction from the substrate board, the PCM absorbs latent heat, facilitating its phase transition from solid to liquid, thereby enhancing the thermal cooling performance of the system. The study compares the thermal performance of three configurations: a system without PCM, a system with minichannel-coupled PCM, and an optimized single minichannel positioned near the heat source. The effectiveness of different PCMs, namely paraffin wax, N-Eicosane, and ATP 78, is also evaluated. Results indicate that N-Eicosane outperforms the other PCMs in providing effective cooling. Specifically, the implementation of N-Eicosane PCM results in a system temperature reduction from 53.234°C in the generic model to 51.520°C. This constitutes a significant temperature drop of 1.74°C compared to the generic model, with an additional reduction of 0.5°C and 1.35°C when compared to paraffin wax and ATP 78 PCM, respectively.