Yue Wu

N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD) and its transformation product 6PPD-quinone (6PPDQ) are emerging tire-derived environmental contaminants, showing a potential tumor-promoting effect. However, their relevance to cutaneous squamous cell carcinoma (cSCC) remains unclear. Here, we used network toxicology and experimental validation to investigate their potential involvement in cSCC progression. A total of 91 candidate genes were identified, and enrichment analysis revealed their participation in oxidative stress response, epithelial proliferation, extracellular matrix degradation, and oncogenic pathways, including PI3K-Akt, MAPK, and IL-17 pathways. Machine learning identified six hub genes: MMP1, MMP9, RECK, LGALS3, GSTP1, and FOXM1. Immune profiling and single-cell RNA-sequencing analysis linked hub-gene expression patterns and tumor microenvironment features, with an emphasis on macrophages, T cells, and keratinocytes. Molecular docking prioritized MMP9 among the six candidate proteins, and molecular dynamics simulations characterized predicted MMP9-ligand complexes. Furthermore, 6PPDQ was found to promote cSCC cell proliferation and tumor growth in both in vitro and in vivo experiments. At the molecular level, 6PPDQ exposure was accompanied by increased PI3K p110α expression, elevated p-AKT/AKT ratio, and MMP9 upregulation, consistent with the computational predictions. Pharmacological AKT inhibition attenuated MMP9 upregulation and the 6PPDQ-associated growth response, while MMP9 silencing reduced 6PPDQ-enhanced invasion and wound closure. Overall, this bioinformatics-led exploratory study suggests that 6PPDQ has tumor-promoting potential in experimental cSCC models and proposes PI3K-Akt/MMP9 activation as a preliminary mechanistic hypothesis. These findings provide candidate targets for future mechanistic and environmental risk studies.

EP251023a is an extragalactic fast X-ray transient (eFXT) that was only detected by the Einstein Probe (EP) and that lacks a gamma-ray counterpart. The prompt emission consisted of a main emission with a duration T ₉₀ = 292 ± 19 s, followed by a long-lasting tail emission that persisted until the observation ended at T ₀ + 1571 s. With the upper limit of Konus–Wind, we derived a conservative upper limit on the isotropic gamma-ray energy E _{γ ,iso} of 5.7 × 10 ⁵² erg for the main emission phase. We identified a redshift of z = 2.232 ± 0.001 based on the strong absorption features in the Keck spectrum, which also indicate a relatively low host-galaxy HI column density. Based on the broadband spectral energy distribution, the late-time light curves show an achromatic plateau, followed by an extremely steep decay with a slope of 3.99 after a break at about 49 ks. This is consistent with a rapidly spinning millisecond magnetar engine. Under the isotropic wind scenario, we obtained an initial period P ₀ < 2.27 ms and a magnetic field strength B _p < 8.33 × 10 ¹⁴ G for the magnetar. If a jet collimation with a typical opening angle of 0.1 rad is considered, these constraints are relaxed to P ₀ < 32.15 ms and B _p < 1.18 × 10 ¹⁶ G. Together with GRB 070707, EP251023a might represent a rare class of optical magnetar-powered internal plateaus with little external-shock contamination. This is different from previous examples that were primarily detected in X-rays. Future discoveries of similar events will help us to clarify the relation between magnetar-powered internal emission observed in the optical band and the emission that is only detected in X-rays.

We conducted a comprehensive study of daily delays using multiwavelength data from a sample of well-studied black hole X-ray binaries, specifically focusing on the sources GX 339–4, 4U 1543–47, and XTE J1550–564. The Interpolated Cross-Correlation Function method was employed to investigate the temporal relationship between the X-ray (Compton component) and optical-infrared (OIR) emissions. Our results show that during the rising hard state, the Compton emission consistently lags behind OIR emission for several days. In contrast, during the decaying hard state, the OIR emission lags behind the Compton emission by approximately 6 to 35 d. This measurement can potentially be used in models of accretion physics and disc instability. We explore the underlying mechanisms responsible for these time delays, highlighting the critical role of viscous heating in the accretion disc in generating OIR luminosity for these sources. The observed time delays during both the rising and decaying hard states are well explained by the disc instability model.

The Galactic fast radio burst (FRB) FRB 200428 was associated with a short X-ray burst (XRB) from the magnetar SGR J1935+2154 during one of its active phases. This FRB-associated XRB exhibits distinct properties compared to other typical XRBs, including a significantly higher cutoff energy and a steeper power-law index. Its recovered X-ray light curve shows a multiple-peak structure, with the time of arrival offset from that of the FRB. These unique features imply a special physical link between the FRB and X-ray emissions. In 2022 October, a similar FRB–XRB association was detected from the same source. In this paper, we propose a model in which the observed spectral and temporal features of the associated XRBs can be attributed to the inverse Compton scattering (ICS) of FRB photons by an extreme pair flow around the light cylinder, with a bulk Lorentz factor of Γ ∼ 10 and a power-law distribution in the comoving frame, characterized by a typical Lorentz factor γ m ′ ∼ 5 × 1 0 4 . This extreme pair flow could originate from the compression of a transient pulse of ∼10⁴⁰−10⁴¹ erg s⁻¹ and the acceleration through magnetic reconnection in the current sheet during magnetar activity. The Doppler-boosted ICS spectra and the arrival time shifts in such a scenario can well explain the observed features of the FRB 200428–associated XRB and can also account for another associated event in 2022.

Accretion of material onto a black hole drags any magnetic fields present inwards, increasing their strength. Theory predicts that sufficiently strong magnetic fields can halt the accretion flow, producing a magnetically arrested disk (MAD). We analyzed archival multiwavelength observations of an outburst from the black hole x-ray binary MAXI J1820+070 in 2018. The radio and optical fluxes were delayed compared with the x-ray flux by about 8 and 17 days, respectively. We interpret this as evidence for the formation of a MAD. In this scenario, the magnetic field is amplified by an expanding corona, forming a MAD around the time of the radio peak. We propose that the optical delay is due to thermal viscous instability in the outer disk.