In this paper, we present a new catalogue of chemically peculiar (CP) stars obtained by compiling publications in which abundances of metals are provided. Our catalogue includes 428 stars for which ...the data were obtained through spectroscopic observations. Most of them (416) are AmFm, HgMn, and ApBp stars. We have used this compilation to proceed to a statistical overview of the abundance anomalies versus the physical parameters of the stars. Spearman’s rank correlation test has been applied, and a significant number of correlations of abundance peculiarities with respect to effective temperature, surface gravity, and rotation velocity have been found. Four interesting cases are discussed in details: the Mn peculiarities in HgMn stars, the Ca correlation with respect to effective temperature in AmFm stars, the case of helium and iron in ApBp stars. Furthermore, we checked for ApBp stars using Anderson–Darling test whether the belonging to a multiple system is a determinant parameter or not for abundance peculiarities.
•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.
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
To enlarge our data base of chemically peculiar stars, we compiled published data concerning the He-weak and He-rich stars observed by high-resolution spectroscopy techniques during last ...decades. Twenty He-weak and 28 He-rich stars have been added to the data base. We have also distinguished roAp stars from stars previously identified as Ap stars. To deepen our knowledge on statistical overview of the abundance anomalies versus the physical parameters of stars, we compared our data with previous compilations. We applied statistical tests on our data and found interesting correlations for effective temperature and surface gravity for all type of stars and a few correlations for projected rotation velocity only for He-rich stars. Because of the lack of the data, we could not check whether being a member of binary system is affecting on chemical peculiarities of those stars.
African swine fever virus manipulates the cell cycle of infected G0 cells by inducing its progression via unblocking cells from the G0 to S phase and then arresting them in the G2 phase. DNA ...synthesis in infected alveolar macrophages starts at 10–12 h post infection. DNA synthesis in the nuclei of G0 cells is preceded by the activation of the viral genes K196R, A240L, E165R, F334L, F778R, and R298L involved in the synthesis of nucleotides and the regulation of the cell cycle. The activation of these genes in actively replicating cells begins later and is less pronounced. The subsequent cell cycle arrest at the G2 phase is also due to the cessation of the synthesis of cellular factors that control the progression of the cell cycle–cyclins. This data describes the manipulation of the cell cycle by the virus to gain access to the nucleotides synthesized by the cell. The genes affecting the cell cycle simply remain disabled until the beginning of cellular DNA synthesis (8–9 hpi). The genes responsible for the synthesis of nucleotides are turned on later in the presence of nucleotides and their transcriptional activity is lower than that during virus replication in an environment without nucleotides.
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
.
Naturally occurring plant flavonoids are a promising class of antiviral agents to inhibit African swine fever virus (ASFV), which causes highly fatal disease in pigs and is a major threat to the ...swine industry. Currently known flavonoids with anti-ASFV activity demonstrate a wide range of antiviral mechanisms, which motivates exploration of new antiviral candidates within this class. The objective of this study was to determine whether other flavonoids may significantly inhibit ASFV infection
in vitro
. We performed a cell-based library screen of 90 flavonoids. Our screening method allowed us to track the development of virus-induced cytopathic effect by MTT in the presence of tested flavonoids. This screening method was shown to be robust for hit identification, with an average Z-factor of 0.683. We identified nine compounds that inhibit ASFV Ba71V strain in Vero cells. Among them, kaempferol was the most potent and exhibited dose-dependent inhibition, which occurred through a virostatic effect. Time-of-addition studies revealed that kaempferol acts on the entry and post-entry stages of the ASFV replication cycle and impairs viral protein and DNA synthesis. It was further identified that kaempferol induces autophagy in ASFV-infected Vero cells, which is related to its antiviral activity and could be partially abrogated by the addition of an autophagy inhibitor. Kaempferol also exhibited dose-dependent inhibition of a highly virulent ASFV Arm/07 isolate in porcine macrophages. Together, these findings support that kaempferol is a promising anti-ASFV agent and has a distinct antiviral mechanism compared to other anti-ASFV flavonoids.
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.
We consider the plane-strain state of a piecewise homogeneous half plane formed by dissimilar infinite strip and half plane with interface finite cracks in the case where the half plane is deformed ...by a finite deformable patch acting upon the free boundary of the half plane. A governing system of integral and integrodifferential equations for the dislocations of displacements of points on the crack edges and the tangential contact stresses acting under the patch is obtained. The solution of this system is constructed with the help of the numerical-analytic method of mechanical quadratures. The numerical analysis is performed, the regularities of the behavior of contact stresses are analyzed, and the specific features of variations of the Cherepanov–Rice
J
-integral are determined depending on the physicomechanical and geometric parameters of the problem.
Aims
Antibiotic resistance of different bacteria requires the development of alternative approaches for overcoming this phenomenon. The antibacterial effects of iron oxide (Fe3O4) nanoparticles (NPs) ...(from 50 to 250 μg ml−1) on Escherichia coli antibiotic‐resistant strains have been aimed.
Methods and Results
The study was performed with ampicillin‐resistant E. coli DH5α‐pUC18 and kanamycin‐resistant E. coli pARG‐25 stains. Specific growth rate of bacteria (μ), lag phase duration and colony‐forming units (CFU) were determined to evaluate growth properties. Fe3O4 NPs (average size of 10·64 ± 4·73 nm) coated with oleic acid and synthesized by modified co‐precipitation method were used. The medium pH, H+ efflux, membrane H+ conductance, redox potential determinations and H2 yield assay were done using potentiometer methods. Growth properties were changed by NPs in concentration‐dependent manner. NPs decreased (up to twofold) H+‐fluxes through bacterial membrane more in E. coli in the presence of the N,N′‐dicyclohexylcarbodiimide, inhibitor of ATPase, indicating that antibacterial activity of these NPs was connected with ATP‐associated metabolism. Membrane‐associated H2 production was lowered up to twofold. Moreover, the synergetic interactions of NPs and antibiotics were found: combination of NPs and antibiotics provided the higher H+ conductance, lower H+‐fluxes and H2 yield.
Conclusions
Fe3O4 NPs can be suggested as alternative antibacterial agents, which can substitute antibiotics in different applications.
Significance and Impact of the Study
The antibacterial effects of Fe3O4 NPs on the growth properties and membrane activity of E. coli antibiotic‐resistant strains have been demonstrated. These NPs have potential as antibacterial agents, which can substitute for antibiotics in bacterial disease treatment in biomedicine, pharmaceutical and environmental applications.
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