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Cell-cell and cell-extracellular matrix (ECM) adhesion regulates fundamental cellular functions and is crucial for cell-material contact. Adhesion is influenced by many factors like affinity and specificity of the receptor-ligand interaction or overall ligand concentration and density. To investigate molecular details of cell ECM and cadherins (cell-cell) interaction in vascular cells functional nanostructured surfaces were used Ligand-functionalized gold nanoparticles (AuNPs) with 6-8 nm diameter, are precisely immobilized on a surface and separated by non-adhesive regions so that individual integrins or cadherins can specifically interact with the ligands on the AuNPs. Using 40 nm and 90 nm distances between the AuNPs and functionalized either with peptide motifs of the extracellular matrix (RGD or REDV) or vascular endothelial cadherins (VEC), the influence of distance and ligand specificity on spreading and adhesion of endothelial cells (ECs) and smooth muscle cells (SMCs) was investigated. We demonstrate that RGD-dependent adhesion of vascular cells is similar to other cell types and that the distance dependence for integrin binding to ECM-peptides is also valid for the REDV motif. VEC-ligands decrease adhesion significantly on the tested ligand distances. These results may be helpful for future improvements in vascular tissue engineering and for development of implant surfaces.
Erfindungsgemäß wird ein Verfahren zur Optimierung des Betriebs eines in einem Regelkreis für einen Aufwärtswandler vorgesehenen digitalen Reglers (30) zur Verfügung gestellt. Das Verfahren umfasst die folgenden Verfahrensschritte: Auswerten (S1) mindestens einer Ausgangsgröße des digitalen Reglers im Betrieb des Aufwärtswandlers. Schätzen (S2) des instantanen Lastwiderstandswertes (RL) in der Strecke des Regelkreises anhand der mindestens einen ausgewerteten Ausgangsgröße. Einstellen (S3) mindestens eines Reglerkoeffizienten des digitalen Reglers anhand des geschätzten instantanen Lastwiderstandswertes (RL) im Betrieb des Aufwärtswandlers. Erfindungsgemäß bedingt eine Veränderung in der Einstellung des mindestens einen Reglerkoeffizienten eine Veränderung der Transitfrequenz im Regelkreis. Ferner wird ein Regelkreis für einen Aufwärtswandler mit einem digitalen Regler zur Verfügung gestellt, welcher eingerichtet ist, um die Schritte des erfindungsgemäßen Verfahrens durchzuführen. Des Weiteren wird ein Computerprogrammprodukt mit computerausführbarem Programmcode zur Durchführung des erfindungsgemäßen Verfahrens zur Verfügung gestellt.
This work presents a fully integrated GaN gate driver in a 180nm HV BCD technology that utilizes high-voltage energy storing (HVES) in an on-chip resonant LC tank, without the need of any external capacitor. It delivers up to 11nC gate charge at a 5V GaN gate, which exceeds prior art by a factor of 45-83, supporting a broad range of GaN transistor types. The stacked LC tank covers an area of only 1.44mm², which corresponds to a superior value of 7.6nC/mm².
In recent years, significant progress was made on switched-capacitor DCDC converters as they enable fully integrated on chip power management. New converter topologies overcame the fixed input-to-output voltage limitation and achieved high efficiency at high power densities. SC converters are attractive to not only mobile handheld devices with small input and output voltages, but also for power conversion in IoTs, industrial and automotive applications, etc. Such applications need to be capable of handling high input voltages of more than 10V. This talk highlights the challenges of the required supporting circuits and high voltage techniques, which arise for high Vin SC converters. It includes level shifters, charge pumps and back-to-back switches. High Vin conversion is demonstrated in a 4:1 SC DCDC converter with an input voltage as high as 17V with a peak efficiency of 45 %, and a buckboost SC converter with an input voltage range starting from 2 up to 13V, which utilizes a total of 17 ratios and achieves a peak efficiency of 81.5 %. Furthermore a highly integrated micro power supply approach is introduced, which is connected directly to the 120/230 Vrms mains, with an output power of 3mW, resulting in a power density >390μW/mm², which exceeds prior art by a factor of 11.
Managing decentralized corporate energy systems is a challenging task for enterprises. However, the integration of energy objectives into business strategy creates difficulties resulting in inefficient decisions. To improve this, practice-proven methods such as the balanced scorecard and enterprise architecture management are transferred to the energy domain. The methods are evaluated based on a case study. Managing multi-dimensionality and high complexity are the main drivers for an effective and efficient energy management system. Both methods show a positive impact on managing decentralized corporate energy systems and are adaptable to the energy domain.
Decentralized energy systems are characterized by an ad hoc planing. The missing integration of energy objectives into business strategy creates difficulties resulting in inefficient energy architectures and decisions. Practice-proven methods such as balanced scorecard, enterprise architecture management and value network approach supports the transformation path towards an effective decentralized system. The methods are evaluated based on a case study. Managing multi-dimensionality, high complexity and multiple actors are the main drivers for an effective and efficient energy management system. The underlying basis to gain the positive impacts of these methods on decentralized corporate energy systems is digitization of energy data and processes.
This paper presents a control strategy for optimal utilization of photovoltaic (PV) generated power in conjunction with an Energy Storage System (ESS). The ESS is specifically designed to be retrofitted into existing PV systems in an end-user application. It can be attached in parallel to the PV system and connects to existing DC/AC inverters. In particular, the study covers the impact such a modification has on the output power of existing PV panels. A distinct degradation of PV output power was found due to the different power characteristics of PV panel and ESS. To overcome such degradation a novel feedback system is proposed. The feedback system continuously modifies the power characteristic of the ESS to match the PV panel and thus achieves optimal power utilization. Impact on PV and power point tracking performance is analyzed. Simulation of the proposed system is performed in MATLAB/Simulink. The results are found to be satisfactory.
A novel configuration of the dual active bridge (DAB) DC/DC converter is presented, enabling more efficient wide voltage range conversion at light loads. A third phase leg as well as a center tapped transformer are introduced to one side of the converter. This concept provides two different turn ratios, thus extending the zero voltage switching operation resulting in higher efficiency. A laboratory prototype was built converting an input voltage of 40V to an output voltage in the range of 350V to 650V. Measurements show a significant increase up to 20% in the efficiency for light-load operation.
Multilevel-cell (MLC) flash is commonly deployed in today’s high density NAND memories, but low latency and high reliability requirements make it barely used in automotive embedded flash applications. This paper presents a time domain voltage sensing scheme that applies a dynamic voltage ramp at the cells’ control gate (CG) in order to achieve fast and reliable sensing suitable for automotive applications.
Pre-clinical evaluation of advanced nerve guide conduits using a novel 3D in vitro testing model
(2018)
Autografts are the current gold standard for large peripheral nerve defects in clinics despite the frequently occurring side effects like donor site morbidity. Hollow nerve guidance conduits (NGC) are proposed alternatives to autografts, but failed to bridge gaps exceeding 3 cm in humans. Internal NGC guidance cues like microfibres are believed to enhance hollow NGCs by giving additional physical support for directed regeneration of Schwann cells and axons. In this study, we report a new 3D in vitro model that allows the evaluation of different intraluminal fibre scaffolds inside a complete NGC. The performance of electrospun polycaprolactone (PCL) microfibres inside 5 mm long polyethylene glycol (PEG) conduits were investigated in neuronal cell and dorsal root ganglion (DRG) cultures in vitro. Z-stack confocal microscopy revealed the aligned orientation of neuronal cells along the fibres throughout the whole NGC length and depth. The number of living cells in the centre of the scaffold was not significantly different to the tissue culture plastic (TCP) control. For ex vivo analysis, DRGs were placed on top of fibre-filled NGCs to simulate the proximal nerve stump. In 21 days of culture, Schwann cells and axons infiltrated the conduits along the microfibres with 2.2 ± 0.37 mm and 2.1 ± 0.33 mm, respectively. We conclude that this in vitro model can help define internal NGC scaffolds in the future by comparing different fibre materials, composites and dimensions in one setup prior to animal testing.