Challenges and Design Requirements for Industrial Applications of AC/AC Power Converters without DC-Link

AC/AC converters that do not have a DC energy storage element, such as a matrix chopper and a matrix converter, are increasingly becoming alternatives to conventional two-stage AC/DC/AC converters and thyristor choppers. In such systems, the main DC-link capacitor does not exist, so the system provides more reliable operation and makes it possible to reduce the financial costs of its construction. It should be noted that AC/AC converters without an energy storage element in a form of DC-link capacitors have not been implemented on an industrial scale. The reasons involve technical aspects and cost components. The main aim of this paper is to present some of the challenges and selected design requirements for industrial applications of AC/AC high reliability power converters

Critical Current Degradation in HTS Tapes for Superconducting Fault Current Limiter under Repeated Overcurrent

Superconducting fault current limiters (SFCL) can be an alternative to conventional devices limiting short-circuit currents in power systems. SFCL use high-temperature superconducting tapes of the second generation (HTS 2G) in SFCL, which, after reaching the characteristic critical current of the tape, go into the resistive state (quenching), limiting the short-circuit current. The critical current determines the moment of activation of the SFCL. Therefore, its value should not change during the operation of the device due to repeated limitation of short-circuit currents. The constancy of the critical current is a prerequisite for proper cooperation with the power system protection devices. Multiple quenching can cause microdamage in the superconducting layers responsible for lowering of the value of the critical current of the HTS tapes. The article presents the research results on the degradation processes of 2G HTS tapes intended for the construction of SFCL due to the action of prospective short-circuit currents with values exceeding the critical current of the tested tapes. The decrease in the value of the critical current of the HTS tape as a result of multiple transitions to the resistive state was investigated. The amount of energy emitted during the test current pulse of 0.2 s duration was determined. The limitation values of the voltage drop on the tape, which does not cause accelerated degradation processes, were defined. The microstructural tests of cross-sections of new HTS tapes subjected to prospective short-circuit currents were performed

Proteomic analysis of tyrosine phosphorylation induced by exogenous expression of oncogenic kinase fusions identified in lung adenocarcinoma

Kinase fusions are considered oncogenic drivers in numerous types of cancer. In lung adenocarcinoma 5–10% of patients harbor kinase fusions. The most frequently detected kinase fusion involves the Anaplastic Lymphoma Kinase (ALK) and Echinoderm Microtubule-associated protein-Like 4 (EML4). In addition, oncogenic kinase fusions involving the tyrosine kinases RET and ROS1 are found in smaller subsets of patients. In this study, we employed quantitative mass spectrometry-based phosphoproteomics to define the cellular tyrosine phosphorylation patterns induced by different oncogenic kinase fusions identified in patients with lung adenocarcinoma. We show that exogenous expression of the kinase fusions in HEK 293T cells leads to widespread tyrosine phosphorylation. Direct comparison of different kinase fusions demonstrates that the kinase part and not the fusion partner primarily defines the phosphorylation pattern. The tyrosine phosphorylation patterns differed between ALK, ROS1, and RET fusions, suggesting that oncogenic signaling induced by these kinases involves the modulation of different cellular processes

An extracellular acidic cleft confers profound H+-sensitivity to epithelial sodium channels containing the δ-subunit in Xenopus laevispH-sensitivity of Xenopus δ-ENaC

The limited sodium availability of freshwater and terrestrial environments was a major physiological challenge during vertebrate evolution. The epithelial sodium channel (ENaC) is present in the apical membrane of sodium-absorbing vertebrate epithelia and evolved as part of a machinery for efficient sodium conservation. ENaC belongs to the degenerin/ENaC protein family and is the only member that opens without an external stimulus. We hypothesized that ENaC evolved from a proton-activated sodium channel present in ionocytes of freshwater vertebrates and therefore investigated whether such ancestral traits are present in ENaC isoforms of the aquatic pipid frog Xenopus laevis. Using whole-cell and single-channel electrophysiology of Xenopus oocytes expressing ENaC isoforms assembled from alpha beta gamma- or delta beta gamma-subunit combinations, we demonstrate that Xenopus delta beta gamma-ENaC is profoundly activated by extracellular acidification within biologically relevant ranges (pH 8.0-6.0). This effect was not observed in Xenopus alpha beta gamma-ENaC or human ENaC orthologs. We show that protons interfere with allosteric ENaC inhibition by extracellular sodium ions, thereby increasing the probability of channel opening. Using homology modeling of ENaC structure and site-directed mutagenesis, we identified a cleft region within the extracellular loop of the delta-subunit that contains several acidic amino acid residues that confer proton-sensitivity and enable allosteric inhibition by extracellular sodium ions. We propose that Xenopus delta beta gamma-ENaC can serve as a model for investigating ENaC transformation from a proton-activated toward a constitutively-active ion channel. Such transformation might have occurred during the evolution of tetrapod vertebrates to enable bulk sodium absorption during the water-to-land transition

Mental Health of Medical and Non-Medical Professionals during the Peak of the COVID-19 Pandemic: A Cross-Sectional Nationwide Study

Background: The study aimed to compare psychopathological expressions during the COVID-19 (novel coronavirus disease 2019) pandemic, as declared on March 11th 2020 by the World Health Organization, with respect to which institutional variables might distinguish the impact of COVID-19 in medical and non-medical professionals. Methods: A cross-sectional study was performed nationwide between 16th March and the 26th April 2020 in Poland. A total of 2039 respondents representing all healthcare providers (59.8%) as well as other professionals filled in the sociodemographic section, the General Health Questionnaire-28 and the author’s questionnaire with questions related to exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the availability of protective measures, quarantine, change of working hours and place of employment during the pandemic, as well as feelings associated with the state of the pandemic. Results: Medical professionals more often presented with relevant psychopathological symptoms (GHQ-28 (General Health Questionnaire-28) total score >24) than the non-medical group (60.8% vs. 48.0%, respectively) such as anxiety, insomnia and somatic symptoms even after adjustment for potential confounding factors. Male sex, older age and appropriate protective equipment were associated with significantly lower GHQ-28 total scores in medical professionals, whereas among non-medical professionals, male sex was associated with significantly lower GHQ-28 total scores. Conclusions: Somatic and anxiety symptoms as well as insomnia are more prevalent among medical staff than workers in other professions. Targeting the determinants of these differences should be included in interventions aimed at restoring psychological well-being in this specific population. Apparently, there are present gender differences in psychological responses that are independent of profession

The cosmic ray detector for the NICA collider

Multi-Purpose Detector (MPD) is a main part of a new Ion Collider fAcility (NICA) located in Dubna, Russia. To increase MPD functionality, it was proposed to add an additional muon trigger system for off-beam calibration of the MPD sub-detectors and for rejection of cosmic ray background during experiments. The system could also be very useful for astrophysical observations of cosmic showers initiated by high energy primary particles. This article describes the main goals of MCORD detector and the early stage of MCORD design, based on plastic scintillators with silicon photomultiplier photodetectors (SiPM) for scintillation readout and electronic system based on MicroTCA standard

The cosmic ray detector for the NICA collider

Multi-Purpose Detector (MPD) is a main part of a new Ion Collider fAcility (NICA) located in Dubna, Russia. To increase MPD functionality, it was proposed to add an additional muon trigger system for off-beam calibration of the MPD sub-detectors and for rejection of cosmic ray background during experiments. The system could also be very useful for astrophysical observations of cosmic showers initiated by high energy primary particles. This article describes the main goals of MCORD detector and the early stage of MCORD design, based on plastic scintillators with silicon photomultiplier photodetectors (SiPM) for scintillation readout and electronic system based on MicroTCA standard