Study on the breakdown characteristics of multiple-reignition secondary arcs on EHV/UHV transmission lines

A long-gap AC arc with a length of more than ten meters (secondary arc) are normally generated at the short-circuit arc channel after a single-phase-to-ground fault. In previous studies, arc breakdowns of secondary arcs have mainly been considered as electrical breakdowns, ignoring the role of heat in the arc channel. Besides, the extinction-reignition theory of secondary arc, i.e., dielectric strength recovery theory, still lack the support of experimental data. In this study, based on the equivalent experiments performed in the laboratory, the influences of compensation degree of transmission lines, initial recovery voltage gradient of air gap, test current, wind speed, and wind direction on the breakdown characteristics of secondary arcs are studied and statistically analyzed. The laws of the transient recovery voltage (TRV) and of the rate of rise of recovery voltage (RRRV) also studied by considering the influencing factors mentioned above. The results of this study will provide a more complete experimental basis for the theory of extinction–reignition of secondary arcs and a deeper understanding of the transient characteristics of arc breakdow

Binding States of Protein–Metal Complexes in Cells

The identification of endogenous proteins as well as their binding to metal ions in living cells is determined by combining pulsed electrophoretic separations with nanoelectrospray ionization followed by mass spectrometric detection. This approach avoids problems resulting from the complicated cellular environment. In this manner, we demonstrate the rapid identification (300 ms or less) of intact proteins from living E. coli cells including the complexation of calmodulin with calcium ion. The latter showed different binding states from those observed in in vitro studies. These observations also reveal in vitro measurements do not necessarily represent the actual situation in living cells. We conclude that the attempted in situ measurement of intracellular proteins with minimal sampling processes should be preferred

Preventing Thermal Osteonecrosis through 3D Printed Ceramic Grinding Tool

Conventional grinding tools in orthopedic surgery and neurosurgery are solid in structure, leading to a limited amount of coolant that can reach the bone surgery zone, and therefore causing localized high-temperature-induced issues (infection, necrosis, and complications). Additive manufacturing allows the incomparable design and manufacturing freedoms and offers the opportunity to redesign the surgery tool to suppress the grinding temperature within a safe range. Here we present a hollow ceramic grinding tool enabled by additive manufacturing. Our CFD simulation and experiments have proved that, owing to the new design, the coolant can better reach the surgery zone, not only helping to restrict the heat accumulations, but also to remove excessive bone debris. In the in vivo test, we found that, the new design produced less apoptosis and edema area to the rat brain in comparison with the conventional tool. This design minimizes the occurrence of complications such as osteonecrosis due to high surgical temperatures, opening new opportunities for the development of orthopedic surgical tools using additive manufacturing technology

Using “On/Off” ¹⁹F NMR/Magnetic Resonance Imaging Signals to Sense Tyrosine Kinase/Phosphatase Activity in Vitro and in Cell Lysates

Tyrosine kinase and phosphatase are two important, antagonistic enzymes in organisms. Development of noninvasive approach for sensing their activity with high spatial and temporal resolution remains challenging. Herein, we rationally designed a hydrogelator Nap-Phe-Phe­(CF₃)-Glu-Tyr-Ile-OH (<b>1a</b>) whose supramolecular hydrogel (i.e., Gel <b>1a</b>) can be subjected to tyrosine kinase-directed disassembly, and its phosphate precursor Nap-Phe-Phe­(CF₃)-Glu-Tyr­(H₂PO₃)-Ile-OH (<b>1b</b>), which can be subjected to alkaline phosphatase (ALP)-instructed self-assembly to form supramolecular hydrogel Gel <b>1b</b>, respectively. Mechanic properties and internal fibrous networks of the hydrogels were characterized with rheology and cryo transmission electron microscopy (cryo-TEM). Disassembly/self-assembly of their corresponding supramolecular hydrogels conferring respective “On/Off” ¹⁹F NMR/MRI signals were employed to sense the activity of these two important enzymes <i>in vitro</i> and in cell lysates for the first time. We anticipate that our new ¹⁹F NMR/magnetic resonance imaging (MRI) method would facilitate pharmaceutical researchers to screen new inhibitors for these two enzymes without steric hindrance

Chrysin protects against cerebral ischemia-reperfusion injury in hippocampus via restraining oxidative stress and transition elements

Chrysin is a natural flavonoid compound that has antioxidant and neuroprotective effects. Cerebral ischemia reperfusion (CIR) is closely connected with increased oxidative stress in the hippocampal CA1 region and homeostasis disorder of transition elements such as iron (Fe), copper (Cu) and zinc (Zn). This exploration was conducted to elucidate the antioxidant and neuroprotective effects of chrysin based on transient middle cerebral artery occlusion (tMCAO) in rats. Experimentally, sham group, model group, chrysin (50.0 mg/kg) group, Ginaton (21.6 mg/kg) group, Dimethyloxallyl Glycine (DMOG, 20.0 mg/kg) + chrysin group and DMOG group were devised. The rats in each group were performed to behavioral evaluation, histological staining, biochemical kit detection, and molecular biological detection. The results indicated that chrysin restrained oxidative stress and the rise of transition element levels, and regulated transition element transporter levels in tMCAO rats. DMOG activated hypoxia-inducible factor-1 subunit alpha (HIF-1α), reversed the antioxidant and neuroprotective effects of chrysin, and increased transition element levels. In a word, our findings emphasize that chrysin plays a critical role in protecting CIR injury via inhibiting HIF-1α against enhancive oxidative stress and raised transition metal levels