Sympathetic Filament Eruptions within a Fan-spine Magnetic System

It is unclear whether successive filament eruptions at different sites within a short time interval are physically connected or not. Here, we present the observations of successive eruptions of a small and a large filament in a tripolar magnetic field region whose coronal magnetic field showed as a fan-spine magnetic system. By analyzing the multiwavelength observations taken by the Solar Dynamic Observatory and the extrapolated three-dimensional coronal magnetic field, we find that the two filaments resided respectively in the two lobes that make up the inner fan structure of the fan-spine magnetic system. In addition, a small fan-spine system was also revealed by the squashing factor Q map, which located in the east lobe of the fan structure of the large fan-spine system. The eruption of the small filament was a failed filament eruption, which did not cause any coronal mass ejection (CME) except for three flare ribbons and two post-flare-loop systems connecting the three magnetic polarities. The eruption of the large filament not only caused similar post-flare-loop systems and flare ribbons, as observed in the small filament eruption, but also a large-scale CME. Based on our analysis results, we conclude that the two successive filament eruptions were physically connected, in which the topology change caused by the small filament eruption is thought to be the physical linkage. In addition, the eruption of the small fan-spine structure further accelerated the instability and violent eruption of the large filament.

Molecular architecture of SARS-CoV-2 envelope by integrative modeling

Despite tremendous efforts by research community during the COVID-19 pandemic, the exact structure of SARS-CoV-2 and related betacoronaviruses remains elusive. Here, we developed and applied an integrative multi-scale computational approach to model the envelope structure of SARS-CoV-2, focusing on studying the dynamic nature and molecular interactions of its most abundant, but largely understudied, M (membrane) protein. The molecular dynamics simulations allowed us to test the envelop stability under different configurations and revealed that M dimers agglomerated into large, filament-like, macromolecular assemblies with distinct molecular patterns formed by M’s transmembrane and intra-virion (endo) domains. These results were in agreement with the experimental data, demonstrating a generic and versatile integrative approach to model the structure of a virus de novo, providing insights into critical roles of structural proteins in the viral assembly and integration, and proposing new targets for the antiviral therapies.

Novel amiloride derivatives that inhibit bacterial motility across multiple strains and stator types

The bacterial flagellar motor (BFM) is a protein complex that confers motility to cells and contributes to survival and virulence. The BFM consists of stators that are ion-selective membrane protein complexes and a rotor that directly connects to a large filament, acting as a propeller. The stator complexes couple ion transit across the membrane to torque that drives rotation of the motor. The most common ion gradients that drive BFM rotation are protons (H+) and sodium ions (Na+). The sodium-powered stators, like those in the PomAPomB stator complex of Vibrio spp, can be inhibited by sodium channel inhibitors, in particular, by phenamil, a potent and widely used inhibitor. However, relatively few new sodium-motility inhibitors have been described since the discovery of phenamil. In this study, we discovered two motility inhibitors HM2-16F and BB2-50F from a small library of previously reported amiloride derivatives. Using a tethered cell assay, we showed that both HM2-16F and BB2-50F had inhibition comparable to that of phenamils on Na+ driven motors at matching concentrations, with an additional ability to inhibit rotation in H+ driven motors. The two compounds did not exhibit adverse effects on bacterial growth at the motility-inhibiting concentration of 10 uM, however toxicity was seen for BB2-50F at 100 uM. We performed higher resolution measurements to examine rotation inhibition at moderate (1 um polystyrene bead) and low loads (60 nm gold bead) and in both the presence and absence of stators. These measurements suggested that the compounds did not inhibit rotation via direct association with the stator, in contrast to the established mode of action of phenamil. Overall, HM2-16F and BB2-50F showed reversible inhibition of motility across a range of loads, in both Na+ and H+ stator types, and in pathogenic and non-pathogenic strains.

A Large Filament and Flares in Active Region NOAA 5669 on September 2, 1989

The behaviour of extended filaments in the vicinity of a new emerging magnetic flux site has been investigated during the 2N/M5.8 flare on September 1 and several flares on September 2, 1989.

Effect of Workpart Curvature on the Stiffness Properties of Circular Filamentary Brushes

In this paper the role which workpart geometry plays in the stiffness properties and contact zone characteristics of circular filamentary brushes is investigated. The problem is examined by employing a recently developed mechanics-based procedure for evaluating large filament deformation, in conjunction with appropriate kinematic constraints for filament tip contact with a smooth, rigid workpart of prescribed constant curvature. Numerical examples for a circular filamentary brush system are presented and discussed for the purpose of illustrating the basic nature of brush stiffness response characteristics for a range of prescribed constant-curvature workpart surfaces.

The effect of metallurgical factors on the quality of fine multifilamentary NbTi superconducting wires

Metallurgical factors during the fabrication process have a large influence on the quality of composite NbTi multifilamentary superconducting wire. The observed critical current density, Jc, is sensitive to microstructure on the scale of the fluxoid-defect interaction, and also to macroscopic variations in filament diameter.Earlier work at the University of Wisconsin, Lawrence Berkeley Laboratory, Wah Chang, and Intermagnetics General Corp. was concentrated on improving the intrinsic Jc for wires with a relatively large filament diameter (~20 μm). By improving homogeneity of the NbTi alloy and by optimizing the drawing-anneal treatment schedule, wires with Jc ∼3000 A/mm2 were produced.

Are cross-bridging structures involved in the bundle formation of intermediate filaments and the decrease in locomotion that accompany cell aging?

Five different fibroblast strains derived from donors of a wide range of ages were used for investigation of senescence-associated changes in the organization of intermediate filaments (IFs) and the activity of cell locomotion. Results of immunofluorescence microscopy demonstrate that, in large and flat in vitro aged fibroblasts, vimentin-containing IFs are distributed as unusually organized large bundles. Electron microscopic examination shows that these large bundles are indeed composed of filaments of 8-10 nm. Such a profile of large bundles is rarely seen in young fibroblasts whose IFs are usually interdispersed among microtubules. Within the large filament bundles of senescent fibroblasts, cross-bridge-like extensions are frequently observed along the individual IFs. Immunogold labeling with antibody to one of the cross-bridging proteins, p50, further illustrates the abundance of interfilament links within the IF bundles. The senescence-related increase in interfilament association was also supported by the results of co-precipitation between vimentin and an associated protein of 50,000 D. Time-lapse cinematographic studies of cell locomotion reveal that accompanying aging, fibroblasts have a significantly reduced ability to translocate across a solid substratum. These results led me to suggest that the increased interfilament links via cross-bridges may in part contribute to the mechanism that orchestrates the formation of large filament bundles. The presence of enormous bundles in the cytoplasm may physically impede the efficiency of locomotion for these nondividing cells.