Abstract
Active galactic nuclei in general, and the supermassive black hole in M87 in particular, show bright and rapid gamma-ray flares up to energies of 100 GeV and above. For M87, the flares show ...multiwavelength components, and the variability timescale is comparable to the dynamical time of the event horizon, suggesting that the emission may come from a compact region near the nucleus. However, the emission mechanism for these flares is not well understood. Recent high-resolution general-relativistic magnetohydrodynamic simulations show the occurrence of episodic magnetic reconnection events that can power flares near the black hole event horizon. In this work, we analyze the radiative properties of the reconnecting current layer under the extreme plasma conditions applicable to the black hole in M87 from first principles. We show that abundant pair production is expected in the vicinity of the reconnection layer, to the extent that the produced secondary pair plasma dominates the reconnection dynamics. Using analytic estimates backed by two-dimensional particle-in-cell simulations, we demonstrate that in the presence of strong synchrotron cooling, reconnection can produce a hard power-law distribution of pair plasma imprinted in the outgoing synchrotron (up to a few tens of MeV) and the inverse-Compton signal (up to TeV). We produce synthetic radiation spectra from our simulations, which can be directly compared with the results of future multiwavelength observations of M87* flares.
Abstract
One scenario for the generation of fast radio bursts (FRBs) is magnetic reconnection in a current sheet of the magnetar wind. Compressed by a strong magnetic pulse induced by a magnetar ...flare, the current sheet fragments into a self-similar chain of magnetic islands. Time-dependent plasma currents at their interfaces produce coherent radiation during their hierarchical coalescence. We investigate this scenario using 2D radiative relativistic particle-in-cell simulations to compute the efficiency of the coherent emission and to obtain frequency scalings. Consistent with expectations, a fraction of the reconnected magnetic field energy,
f
∼ 0.002, is converted to packets of high-frequency fast magnetosonic waves, which can escape from the magnetar wind as radio emission. In agreement with analytical estimates, we find that magnetic pulses of 10
47
erg s
−1
can trigger relatively narrowband GHz emission with luminosities of approximately 10
42
erg s
−1
, sufficient to explain bright extragalactic FRBs. The mechanism provides a natural explanation for a downward frequency drift of burst signals, as well as the ∼100 ns substructure recently detected in
FRB 20200120E
.
The African swine fever (ASF) virus (ASFV) and ASF-like viral sequences were identified in human samples and sewage as well as in different water environments. Pigs regularly experience infections by ...the ASFV. The considerable stability of the virus in the environment suggests that there is ongoing and long-term contact between humans and the ASFV. However, humans exhibit resistance to the ASFV, and the decisive factor in developing infection in the body is most likely the reaction of target macrophages to the virus. Therefore, this study aimed to characterize the responses of human macrophages to the virus and explore the distinct features of the viral replication cycle within human macrophages.
The ASFV Armenia/07 strain was used in all experiments. In this study, quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the ASFV gene expression; flow cytometry analysis was performed to evaluate the effects of the inactive and active ASFV (inASFV and aASFV) treatments on the phenotype of THP-1-derived macrophages (Mφ0) and inflammatory markers. Moreover, other methods such as cell viability and apoptosis assays, staining techniques, phagocytosis assay, lysosome-associated membrane protein (LAMP-1) cytometry, and cytokine detection were used during experiments.
Our findings showed that the virus initiated replication by entering human macrophages. Subsequently, the virus shed its capsid and initiated the transcription of numerous viral genes, and at least some of these genes executed their functions. In THP-1-derived macrophages (Mφ0), the ASFV implemented several functions to suppress cell activity, although the timing of their implementation was slower compared with virus-sensitive porcine alveolar macrophages (PAMs). Additionally, the virus could not complete the entire replication cycle in human Mφ0, as indicated by the absence of viral factories and a decrease in infectious titers of the virus with each subsequent passage. Overall, the infection of Mφ0 with the ASFV caused significant alterations in their phenotype and functions, such as increased TLR2, TLR3, CD80, CD36, CD163, CXCR2, and surface LAMP-1 expression. Increased production of the tumor necrosis factor (TNF) and interleukin (IL)-10 and decreased production of interferon (IFN)-α were also observed. Taken together, the virus enters human THP-1-derived macrophages, starts transcription, and causes immunological responses by target cells but cannot complete the replicative cycle.
These findings suggest that there may be molecular limitations within human macrophages that at least partially restrict the complete replication of the ASFV. Understanding the factors that hinder viral replication in Mφ0 can provide valuable insights into the host-virus interactions and the mechanisms underlying the resistance of human macrophages to the ASFV.
First cases of clinically uncommon African swine fever (ASF), caused by virus genotype II are described in this article. These cases occurred in Armenia, Tavush region, Dilijan municipality in 2011. ...The aim of this study was to identify and describe the new pathogenic forms of ASF in Armenia.
The isolation and identification of ASF virus (ASFV) were carried out using conventional techniques. Clinical signs of infection were recorded daily. Gross anatomical pathology characteristics were observed during routine postmortem examinations. Blood and serum were obtained by puncture of the jugular vein using a vacutainer system.
The presence of ASFV DNA in the spleens was confirmed by polymerase chain reaction. Sequenced sections of p72 showed phylogenetic identity to genotype 2. The pathology exhibits unusual manifestations of the main disease. The unusual form of ASF demonstrates characteristics of a subacute form of the disease, with the possibility of conversion to a chronic form. Decreased lethality, low level of hemorrhages, and absence of severe pancytopenia in smears from spleen, lymph nodes, and blood are common features of the new form of ASF. Unlike severe thrombocytopenia in the typical ASF, the unusual form exhibited moderate or minor decrease of this feature. Despite a moderate decrease in hemadsorption titers, the unusual pattern of the disease was characterized by viremia and the presence of the virus in the visceral organs, including the brain.
Our data allow assuming that new nosological form of ASF (genotype II) may present as a transitional form of the disease with the possibility of chronization.
Based on the linear electron accelerator LUE-75 of the A.I. Alikhanyan National Scientific Laboratory a technique for obtaining controlled primary electron beams with an intensity of 10–20 electrons ...per second in the energy range 15–75 MeV for elementary particle detectors calibration was developed and used. Joint work with the V.P. Dzhelepov Laboratory of Nuclear Problems (JINR, Dubna, RF) showed the efficiency of the technique.
A series of pyrrolidine-2.5-diones with benzenesulfonamide substituents on the ring N atom were synthesized from substituted dicarboxylic acids and various benzenesulfonamides. The antibacterial and ...neurotropic activities of the synthesized compounds were tested. Several compounds exhibited pronounced anticonvulsant activity although most compounds had weak antimicrobial properties.
•Ecological niches for ASFV.•Invertebrates as experimental models.•ASFV survival.
In this study, we investigated the possible biological factors affecting the survival of the African swine fever ...virus (ASFV) in the environment and their potential to influence the ecology of the ASFV. Specifically, we tested the survival and replication of ASFV in four phylogenetically distinct organisms: Paramecium caudatum, Dendrobaena alpine, Aedes aegypti andXeropicta derbentina using qReal-Time PCR and hemadsorbtion analysis. Levels of ASFV in earthworms (Dendrobaena alpina) and soil declined at similar rates, suggesting that earthworms likely have no influence on the ecology of the ASFV. Ciliates (Paramecium caudatum) significantly increase the rate of ASFV disappearance from the aquatic environment, probably using the virus as a food source. Mosquitoes (Aedes aegypti) do not provide significant support for the persistence of ASF virus in the environment, with no evidence for transmission to their offspring or pigs that ingested mosquitoes. ASFV persisted for much longer in air-breathing land snails (Xeropicta derbentina) than in the soil. Moreover, transcription of viral genes was maintained within the snail, although the question of full-fledged viral replication is still open. In addition, the active movements of snails suggests that they could play a role in the spread of the virus. The virus is likely to be localized in the intestines of snails as it is regularly excreted from their feces. These results highlight the importance of investigating invertebrates for understanding ASFV surviving, spreading and transmission in natural populations with zoonotic transmission potential.
Aseries of diethyl esters of 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxylic acids (β-cycloketols) were synthesized by Knoevenagel condensation. A method for their dehydration was ...developed. Peculiarities of the condensation depending on the reaction conditions were pointed out. All obtained cycloketols and some dehydrated analogs exhibited more or less pronounced anticonvulsant activity in the corazole seizure test in mice.
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