Summary
Purpose: Dysfunction of the blood–brain barrier (BBB) is a common finding during seizures or following epileptogenic brain injuries, and experimentally induced BBB opening promotes seizures ...both in naive and epileptic animals. Brain albumin extravasation was reported to promote hyperexcitability by inducing astrocytes dysfunction. To provide in vivo evidence for a direct role of extravasated serum albumin in seizures independently on the pathologic context, we did the following: (1) quantified the amount of serum albumin extravasated in the rat brain parenchyma during status epilepticus (SE); (2) reproduced a similar concentration in the hippocampus by intracerebroventricular (i.c.v.) albumin injection in naive rats; (3) measured electroencephalography (EEG) activity in these rats, their susceptibility to kainic acid (KA)–induced seizures, and their hippocampal afterdischarge threshold (ADT).
Methods: Brain albumin concentration was measured in the rat hippocampus and other forebrain regions 2 and 24 h after SE by western blot analysis. Brain distribution of serum albumin or fluorescein isothiocyanate (FITC)‐albumin was studied by immunohistochemistry and immunofluorescence, respectively. Naive rats were injected with rat albumin or FITC‐albumin, i.c.v., to mimic the brain concentration attained after SE, or with dextran used as control. Inflammation was evaluated by immunohistochemistry by measuring glial induction of interleukin (IL)‐1β. Western blot analysis was used to measure inward rectifying potassium channel subunit Kir4.1 protein levels in the hippocampus. Seizures were induced in rats by intrahippocampal injection of 80 ng KA and quantified by EEG analysis, 2 or 24 h after rat albumin or dextran administration. ADT was measured by electrical stimulation of the hippocampus 3 months after albumin injection. In these rats, EEG was continuously monitored for 2 weeks to search for spontaneous seizures.
Key Findings: The hippocampal serum albumin concentration 24 h post‐SE was 0.76 ± 0.21 μm. Similar concentrations were measured in other forebrain regions, whereas no changes were found in cerebellum. The hippocampal albumin concentration was similarly reproduced in naive rats by i.c.v. administration of 500 μg/4 μl rat albumin: albumin was predominantly detected extracellularly 2 h after injection, whereas at 24 h it was visible inside pyramidal neurons and in only a few scattered chondroitin sulphate proteoglycan (NG2)‐positive cells, but not in glial fibrillary acidic protein (GFAP)‐positive astrocytes or CR‐3 complement receptor (OX‐42)‐positive microglia. The presence of albumin in naive rat hippocampus was associated with induced IL‐1β in GFAP‐positive astrocytes and a concomitant tissue down‐regulation of Kir4.1. Spiking activity was evoked by albumin in the hippocampus lasting for 2 h. When KA was intrahippocampally applied either 2 or 24 h after albumin injection, the number of total interictal spikes in 3 h EEG recording was significantly increased by twofold on average. Three months after albumin injection, neither albumin nor inflammation was detected in brain tissue; at this time, the ADT was reduced by 50% but no spontaneous seizures were observed.
Significance: Transient hippocampal exposure to albumin levels similar to those attained after prominent BBB breakdown resulted in increased seizure susceptibility and long‐term reduction in seizure threshold, but it did not evoke spontaneous seizures. These effects may be mediated by albumin‐induced astrocytes dysfunction and the associated induction of proinflammatory molecules.
Increasing fault current demands for future high voltage grids may not only exceed technical feasible limits for current breaking but they may have also strong impact on system costs if all ...components of the affected network must be designed or replaced for such increasing stresses. Superconducting fault current limiter technology may deliver a cost effective alternative by keeping the fault currents within common values. For the 380 kV voltage range such fault current limiters are supposed to be designed for similar high voltage test values and waveforms as power transformers of this grid level. In combination with a superconductor tape length of about 100 km per phase, it can be expected that 380 kV superconducting fault current limiters for one phase have sizes similar to 3-phase 380 kV power transformers. In this article, field limit estimations were done for the different insulation materials since experimental data with high voltage of several 100 kV or above 1 MV are rare or still missing for the assumed cryogenic temperature and pressure range. A principle high voltage design for one phase of a 380 kV/5 kA superconducting fault current limiter was performed based on these maximum field values. The design includes capacitor bushings and post insulators.
This study conducts a comparative life cycle assessment of two different types of cooling systems for a 1 km long, 10 kV concentric three-phase high-temperature superconducting cable. In an open ...cooling system, the required cooling energy is provided by evaporating liquid nitrogen in a subcooler resulting in a constant loss of liquid nitrogen. As a consequence, liquid nitrogen must constantly be reproduced and transported to the cooling unit. Alternatively, a closed cooling system can be used in which liquid nitrogen is electrically re-cooled using a cryocooler. This results in a higher on-site electricity consumption but simultaneously removes any liquid nitrogen losses. It is shown that the use of a closed cooling system does not only reduce the total system losses but also improves the environmental performance by 4-24% depending on the examined environmental impact category. If the cryocooler is powered by renewable energies only, the environmental savings can be increased even further.
The enhanced thermal stability of no-insulation superconducting coils, due to the absent turn-to-turn insulation is demonstrated in several publications. With the self-protecting properties of these ...coils, the application of second generation high temperature superconductors in real energy applications can be simplified, regarding quench detection and protection. Furthermore, it enables a system design with superconducting coils operating closer to their critical current limitation compared to their insulated counterparts. The usage of superconducting materials, improving the power density in wind turbine generators is an ongoing research topic. As a result, the design and construction of a 10 kW laboratory demonstrator is intended. Therefore, six double pancake racetrack coils are manufactured with two different superconducting tape architectures and compared with respect to the critical current, turn-to-turn resistance and transient performance in liquid nitrogen at 77 K. The superconducting coils are joined together to a six-pole stator system for the installation in the 10 kW generator demonstrator. All 12 pancakes reach the expected critical current and show a similar transient response of the magnetic field in the individual measurements. However, the series-connected stator system has a much longer field delay than the individual pancakes, which cannot be sufficiently explained by the typical equivalent circuit diagram for no-insulation coils.
This paper discusses the design, set-up and short-circuit testing of an air coil superconducting fault current limiter demonstrator. The demonstrator was specified for 60 kVA, 400 V, z = 6%. It ...consists of a primary winding made of copper, which is basically the equivalent of an air core reactor and a secondary superconducting winding made of commercially available (RE)BCO tapes, which are individually short-circuited. Both windings are inductively coupled and intended to work in liquid nitrogen. The measurements results show significantly lower impedance during normal operation compared to the air core reactor. If a fault current occurs the induced current in the secondary winding quenches the superconducting tapes, which generates a resistance and significantly increasing the impedance of the limiter. The built demonstrator achieves a current limiting capability of up to 40% for fault currents 17 times higher than the nominal current. The demonstrator proves the concept of the air coil superconducting fault current limiter and verifies the underlying design method.
Slow-read DDoS attacks are complex to detect and mitigate. Although existing tools allow one to identify these threats, these tools mainly generate alerts. However, in real scenarios, a large number ...of threat detection alerts will put the security workforce in a bottleneck, as they will not be able to implement mitigation actions in a complete and timely manner. Furthermore, since most existing security solutions for DDoS attack mitigation are tested using datasets and simulated scenarios, their applicability to production networks could be unfeasible or ineffective due to possibly incomplete assumptions in their design. Therefore, automated security solutions against DDoS attacks are needed not only to be designed but also to be implemented and evaluated in real scenarios. This study presents a Software-Defined Networking (SDN)-based security framework that automates the monitoring, detection, and mitigation of slow-rate DDoS attacks. The framework is implemented in a physical network that uses equipment from the European Experimental Facility Smart Networks for Industry (SN4I, https://i2t.ehu.eus/en/resources/sn4i). The results demonstrate that the framework effectively mitigates malicious connections, with a mitigation efficiency between 91.66% - 100% for different conditions of the number of attackers and victims. In addition, the SDN-SlowRate-DDoS dataset (https://dx.doi.org/10.21227/amrt-8y98) is presented which contains multiple experiments of slow-rate DDoS threats performed on the real testbed. The resources provided in this security dataset are useful to the scientific and industry communities in designing and testing realistic solutions for intrusion detection systems.
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