Field-Aligned and Ionospheric Currents by AMPERE and SuperMAG During HSS/SIR-Driven Storms

This study considers 28 geomagnetic storms with Dst $\leq-50$ nT driven by high-speed streams (HSSs) and associated stream interaction regions (SIRs) during 2010-2017. Their impact on ionospheric horizontal and field-aligned currents (FACs) have been investigated using superposed epoch analysis of SuperMAG and AMPERE data, respectively. The zero epoch ($t_0$) was set to the onset of the storm main phase. Storms begin in the SIR with enhanced solar wind density and compressed southward oriented magnetic field. The integrated FAC and equivalent currents maximise 40 and 58 min after $t_0$, respectively, followed by a small peak in the middle of the main phase ($t_0$+4h), and a slightly larger peak just before the Dst minimum ($t_0$+5.3h). The currents are strongly driven by the solar wind, and the correlation between the Akasofu $\varepsilon$ and integrated FAC is $0.90$. The number of substorm onsets maximises near $t_0$. The storms were also separated into two groups based on the solar wind dynamic pressure p_dyn in the vicinity of the SIR. High p_dyn storms reach solar wind velocity maxima earlier and have shorter lead times from the HSS arrival to storm onset compared with low p_dyn events. The high p_dyn events also have sudden storm commencements, stronger solar wind driving and ionospheric response at $t_0$, and are primarily responsible for the first peak in the currents after $t_0$. After $t_0+2$ days, the currents and number of substorm onsets become higher for low compared with high p_dyn events, which may be related to higher solar wind speed.publishedVersio

Effect of ICME-Driven Storms on Field-Aligned and Ionospheric Currents From AMPERE and SuperMAG

Funding Information: This work was supported by the Academy of Finland project 314664 and 314670. We thank the AMPERE team and the AMPERE Science Center for providing the Iridium derived data products ( https://ampere.jhuapl.edu/ ). For the ground magnetometer data and substorm onset list, we gratefully thank the SuperMAG collaboration and all organizations involved ( https://supermag.jhuapl.edu/info/ ). For the geomagnetic indices, solar wind and interplanetary magnetic field data, we gratefully thank NASA/GSFC's Space Physics Data Facility's OMNIWeb ( https://omniweb.gsfc.nasa.gov/ ). Funding Information: This work was supported by the Academy of Finland project 314664 and 314670. We thank the AMPERE team and the AMPERE Science Center for providing the Iridium derived data products (https://ampere.jhuapl.edu/). For the ground magnetometer data and substorm onset list, we gratefully thank the SuperMAG collaboration and all organizations involved (https://supermag.jhuapl.edu/info/). For the geomagnetic indices, solar wind and interplanetary magnetic field data, we gratefully thank NASA/GSFC's Space Physics Data Facility's OMNIWeb (https://omniweb.gsfc.nasa.gov/). Publisher Copyright: © 2022. The Authors.Peer reviewe

Mean Field Network based Graph Refinement with application to Airway Tree Extraction

We present tree extraction in 3D images as a graph refinement task, of obtaining a subgraph from an over-complete input graph. To this end, we formulate an approximate Bayesian inference framework on undirected graphs using mean field approximation (MFA). Mean field networks are used for inference based on the interpretation that iterations of MFA can be seen as feed-forward operations in a neural network. This allows us to learn the model parameters from training data using back-propagation algorithm. We demonstrate usefulness of the model to extract airway trees from 3D chest CT data. We first obtain probability images using a voxel classifier that distinguishes airways from background and use Bayesian smoothing to model individual airway branches. This yields us joint Gaussian density estimates of position, orientation and scale as node features of the input graph. Performance of the method is compared with two methods: the first uses probability images from a trained voxel classifier with region growing, which is similar to one of the best performing methods at EXACT'09 airway challenge, and the second method is based on Bayesian smoothing on these probability images. Using centerline distance as error measure the presented method shows significant improvement compared to these two methods.Comment: 10 pages. Preprin

A finite loop space not rationally equivalent to a compact Lie group

We construct a connected finite loop space of rank 66 and dimension 1254 whose rational cohomology is not isomorphic as a graded vector space to the rational cohomology of any compact Lie group, hence providing a counterexample to a classical conjecture. Aided by machine calculation we verify that our counterexample is minimal, i.e., that any finite loop space of rank less than 66 is in fact rationally equivalent to a compact Lie group, extending the classical known bound of 5.Comment: 8 page

Glucose transporters: production, crystallization and inhibition

Glucose transporters (GLUTs) comprise a family of 14 membrane proteins that regulate glucose uptake into the cell. Different types of GLUTs are expressed in various tissues and play a crucial role in glucose metabolism. Cancer cells are highly dependant on glucose and therefore GLUTs are possible drug targets for cancer therapy. In order to block the glucose uptake facilitated by GLUTs, various inhibitors are studied and both natural and synthetic compounds having an inhibitory effect on glucose uptake have been discovered. High resolution X-ray structure of the GLUT-inhibitor complex would provide a detailed understanding of protein-inhibitor interactions and contribute to facilitating the development of new derivatives. The focus of this study is on a glucose transporter 1 (GLUT1). The GLUT1 has been produced and crystallization trials set up, which resulted in microcrystals. A series of salicylketoxime based compounds have been shown to inhibit GLUT1 and two lead compounds displaying the highest inhibition have been identified in a giant vesicle assay. The main goal of the study is to determine the structure of the GLUT1 with selected inhibitors. Moreover, studies on one more glucose transporter GLUT3 are carried out to investigate the selectivity of the salcylketoxime compounds

Molecular Basis of Enhanced Activity in Factor VIIa-Trypsin Variants Conveys Insights into Tissue Factor-mediated Allosteric Regulation of Factor VIIa Activity

The complex of coagulation factor VIIa (FVIIa), a trypsin-like serine protease, and membrane-bound tissue factor (TF) initiates blood coagulation upon vascular injury. Binding of TF to FVIIa promotes allosteric conformational changes in the FVIIa protease domain and improves its catalytic properties. Extensive studies have revealed two putative pathways for this allosteric communication. Here we provide further details of this allosteric communication by investigating FVIIa loop swap variants containing the 170 loop of trypsin that display TF-independent enhanced activity. Using x-ray crystallography, we show that the introduced 170 loop from trypsin directly interacts with the FVIIa active site, stabilizing segment 215–217 and activation loop 3, leading to enhanced activity. Molecular dynamics simulations and novel fluorescence quenching studies support that segment 215–217 conformation is pivotal to the enhanced activity of the FVIIa variants. We speculate that the allosteric regulation of FVIIa activity by TF binding follows a similar path in conjunction with protease domain N terminus insertion, suggesting a more complete molecular basis of TF-mediated allosteric enhancement of FVIIa activity