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A number of double coronal X-ray sources have been observed during solar flares by RHESSI, where the two sources reside at different sides of the inferred reconnection site. However, where and how these X-ray-emitting electrons are accelerated remains unclear. Here we present the first model of the double coronal hard X-ray (HXR) sources, where electrons are accelerated by a pair of termination shocks driven by bidirectional fast reconnection outflows. We model the acceleration and transport of electrons in the flare region by numerically solving the Parker transport equation using velocity and magnetic fields from the macroscopic magnetohydrodynamic simulation of a flux rope eruption. We show that electrons can be efficiently accelerated by the termination shocks and high-energy electrons mainly concentrate around the two shocks. The synthetic HXR emission images display two distinct sources extending to >100 keV below and above the reconnection region, with the upper source much fainter than the lower one. The HXR energy spectra of the two coronal sources show similar spectral slopes, consistent with the observations. Our simulation results suggest that the flare termination shock can be a promising particle acceleration mechanism in explaining the double-source nonthermal emissions in solar flares. [ABSTRACT FROM AUTHOR]

As an important coding scheme in modern distributed storage systems, locally repairable codes (LRCs) have attracted a lot of attentions from perspectives of both practical applications and theoretical research. As a major topic in the research of LRCs, bounds and constructions of the corresponding optimal codes are of particular concerns. In this work, codes with $(r,\delta)$ -locality which have optimal minimal distance w.r.t. the bound given by Prakash et al. are considered. Through parity-check matrix approach, constructions of both optimal $(r,\delta)$ -LRCs with all symbol locality ($(r,\delta)_{a}$ -LRCs) and optimal $(r,\delta)$ -LRCs with information locality ($(r,\delta)_{i}$ -LRCs) are provided. As a generalization of a work of Xing and Yuan, these constructions are built on a connection between sparse hypergraphs and optimal $(r,\delta)$ -LRCs. With the help of constructions of large sparse hypergraphs, the lengths of codes obtained from our construction can be super-linear in the alphabet size. This improves upon previous constructions when the minimal distance of the code is at least $3\delta +1$. As two applications, optimal H-LRCs with super-linear lengths and GSD codes with unbounded lengths are also constructed. [ABSTRACT FROM AUTHOR]

As a crucial technique for integrated circuits (IC) test response compaction, X-compact employs a special kind of codes called X-codes for reliable compressions of the test response in the presence of unknown logic values (Xs). From a combinatorial view point, Fujiwara and Colbourn introduced an equivalent definition of X-codes and studied X-codes of small weights that have good detectability and X-tolerance. An $({\it\text { m, n, d, x}})~\text {X}$ -code is an $\text {m}\times \text {n}$ binary matrix with column vectors as its codewords. The parameters ${\it\text { d, x}}$ correspond to the test quality of the code. In this paper, bounds and constructions for constant weighted X-codes are investigated. First, we obtain a general result on the maximum number of codewords n for an $({\it\text { m, n, d, x}})~\text {X}$ -code of weight w, and we further improve this lower bound for the case with $\text {x}=2$ and $\text {w}=3$ through the probabilistic method. Then, using tools from additive combinatorics and finite fields, we present some explicit constructions for constant weighted X-codes with $\text {d}=3,7$ and $\text {x}=2$ , which are optimal for the case when $\text {d}=3, \text {w}=4$ and nearly optimal for the case when $\text {d}=3,\text {w}=3$. We also consider a special class of X-codes introduced by Fujiwara and Colbourn and improve the best known lower bound on the maximum number of codewords for this kind of X-codes. [ABSTRACT FROM AUTHOR]

Abstract: The anti-inflammatory effects of pseudoephedrine/ephedrine were investigated using the experimental model of lipopolysaccharide (LPS)-induced acute liver failure in d-galactosamine (d-GalN)-sensitised male rats in order to elucidate effects other than sympathomimetic effects. Rats were intraperitoneally injected with d-GalN (400mg/kg) and LPS (40μg/kg) to induce acute liver failure. The treatment groups were then intraperitoneally administered pseudoephedrine/ephedrine at 0h and 4h after induction and the activation induced by treatment with pseudoephedrine and/or LPS on the primary Kupffer cells (KCs) was monitored. Compared with controls induced by GalN/LPS alone, pseudoephedrine dramatically reduced the infiltration of inflammatory cells and bile ductular hyperplasia and hepatic necrosis observed in liver sections. It inhibited both hepatocellular apoptosis and the expression of monocyte chemotactic protein-1. It lowered the production of tumour necrosis factor-α (TNF-α) in the beginning of acute liver failure induced by d-GalN/LPS. Correspondingly, levels of alanine aminotransferase (ALT), total bilirubin (TBIL) and malondialdehyde were attenuated. Ephedrine demonstrated all these identical protective effects as well. In addition, pseudoephedrine significantly suppressed the production of p-IκB-α, reducing the degradation of sequestered nuclear factor kappa B (NF-κB) in the cytoplasm, and inhibited the translocation of NF-κB/p65 to the nucleus, the transcription of TNF-α mRNA and the production of TNF-α in primary KCs. These results suggest that pseudoephedrine and ephedrine have a potent anti-inflammatory activity against d-GalN/LPS-induced acute liver failure in rats, and this comprehensive anti-inflammatory effect may result from the inhibition of TNF-α production. [Copyright &y& Elsevier]

Let { (A i , B i) } i = 1 m be a collection of pairs of sets with | A i | = a and | B i | = b for 1 ≤ i ≤ m. Suppose that A i ∩ B j = 0̸ if and only if i = j , then by the famous Two Families Theorem of Bollobás, we have the size of this collection m ≤ a + b a . In this paper, we consider a variant of this problem by requiring { A i } i = 1 m to be intersecting additionally. Using exterior algebra method, we prove a weighted Bollobás-type theorem for finite dimensional real vector spaces under these constraints. As a consequence, we obtain a similar theorem for finite sets, which settles a recent conjecture of Gerbner et al. (2020). Moreover, we also determine the unique extremal structure of { (A i , B i) } i = 1 m for the primary case of the theorem for finite sets. [ABSTRACT FROM AUTHOR]

Effects of the extreme-ultraviolet (EUV) late phase of solar flares on the ionosphere were rarely studied. Here we simulated such effects on the ionospheric electron density using an ionosphere−thermosphere coupled model driven by the realistic solar spectrum observed during the X1.8 flare on 2012 October 23. Global total electron content (TEC) observations and simulations showed that the dayside ionospheric TEC during the EUV late phase increased more than that of the flare's main phase. We examined the performance of the model for flares with EUV late phase. The results showed that the F-region electron density enhancement and recovery did not vary in the same pace as the temporal variations of the EUV late phase, and the presence of the EUV late phase prolonged the recovery of electron density by ∼9 hr. We also found that the enhancement in electron density was mainly determined by the chemical production, while the recovery of electron density was primarily controlled by the electric field transport effects. This study enhanced understanding of the intricate physical and photochemical processes governing Earth's space environment and similar planetary systems during solar flare events with EUV late phase. [ABSTRACT FROM AUTHOR]

Ring-beam energetic electrons can drive two different kinetic instabilities, including the bump-on-tail instability by the beam component and the electron cyclotron maser instability by the ring component. It is critical to understand how the two instabilities develop and interact, and how their competition for free energy affects the wave modes and further plasma emission process. Here, we present fully kinetic particle-in-cell simulations of the ring-beam interaction with weakly magnetized plasmas of coronal conditions. We found that both the beam-Langmuir (BL) mode and the upper-hybrid (UH) mode can be excited efficiently, along with significant fundamental and harmonic plasma emissions. In comparison with the corresponding pure-beam case, in the ring-beam case, the BL mode has a suppressed range of k ⊥ , slower damping and thus stronger intensity, and the fundamental emission is considerably stronger, while the harmonic emission has comparable intensity yet being more directional. We further investigated the effect of the pitch angle (α) of the ring-beam distribution, found that the (1) BL mode is more limited in the range of k ⊥ with larger α and (2) the UH mode is excited in localized blobs that can be clustered with a straight line whose slope is ∼ cot α. Most of these intriguing results can be interpreted with the linear kinetic theory. [ABSTRACT FROM AUTHOR]

Experiments of generation of quasi-perpendicular collisionless shocks driven by laser plasma were performed at the Shenguang-II laser facility with intense lasers. Here, using a 1D particle-in-cell simulation code including protons, carbon ions, and electrons, we investigate the experimental shock formation via the interaction between the laser-ablated piston and ambient plasma magnetized by a large pre-existing magnetic field and the associated ion dynamics in more detail. Simulation results show that, given enough time and space, ambient protons and carbon ions can be reflected at the piston–ambient interface successively, which leads to the formation of corresponding shocks before the piston and interface. Electric fields associated with the initial interaction known as Larmor coupling and the shocks may accelerate ambient protons, carbon ions reflected at the interface or shocks, and piston ones transmitted to the ambient region before shock formation. [ABSTRACT FROM AUTHOR]

The standard theory of plasma emission is based on kinetic couplings between a single beam of energetic electrons and unmagnetized thermal plasmas, involving multistep nonlinear waveâ€"particle and waveâ€"wave interactions. The theory has not yet been completely verified with fully kinetic electromagnetic particle-in-cell (PIC) simulations. Earlier studies, greatly limited by available computational resources, are controversial regarding whether the fundamental emission can be generated according to the standard theory. To resolve the controversy, we conducted PIC simulations with a large domain of simulations and a large number of macroparticles, among the largest ones of similar studies. We found significant fundamental emission if the relative beam density is small enough (say, ≤0.01), in line with an earlier study with a much smaller domain; the relative intensity (normalized by the total initial beam energy) of all modes, except the mode associated with the beam-electromagnetic Weibel instability, decreases with the increasing relative density of the beam. We also found a significant transverse magnetic component associated with the superluminal Langmuir turbulence, which has been mistakenly regarded as evidence of the F emission in the earlier study. Further investigations are required to reveal their origin. [ABSTRACT FROM AUTHOR]

Background: Chronic hepatitis b (CHB) is one of the most serious viral diseases threatening human health by putting patients at lifelong risk of cirrhosis and hepatocellular carcinoma (HCC). Although some proofs of altered metabolites in CHB were accumulated, its metabolic mechanism remains poorly understood. Analyzing covariations between metabolites may provide new hints toward underlying metabolic pathogenesis in CHB patients. Methods: The present study collected paired urine and serum samples from the same subjects including 145 CHB and 23 healthy controls. A large-scale analysis of metabolites’ covariation within and across biofluids was systematically done to explore the underlying biological evidences for reprogrammed metabolism in CHB. Randomization and relative ranking difference were introduced to reduce bias caused by different sample size. More importantly, functional indication was interpreted by mapping differentially changed covariations to known metabolic pathways. Results: Our results suggested reprogrammed pathways related to glycine metabolism, fatty acids metabolism and TCA cycle in CHB patients. With further improvement, the covariation analysis combined with network association study would pave new alternative way to interpret functional clues in clinical multi-omics data. [ABSTRACT FROM AUTHOR]

Simultaneous radio and extreme ultraviolet (EUV)/white-light imaging data are examined for a solar type II radio burst occurring on 2010 March 18 to deduce its source location. Using a bow-shock model, we reconstruct the three-dimensional EUV wave front (presumably the type-II-emitting shock) based on the imaging data of the two Solar TErrestrial RElations Observatory spacecraft. It is then combined with the Nançay radio imaging data to infer the three-dimensional position of the type II source. It is found that the type II source coincides with the interface between the coronal mass ejection (CME) EUV wave front and a nearby coronal ray structure, providing evidence that the type II emission is physically related to the CME-ray interaction. This result, consistent with those of previous studies, is based on simultaneous radio and EUV imaging data for the first time. [ABSTRACT FROM AUTHOR]