Kinematics and Collimation of the Two-Sided Jets in NGC 4261: VLBI Study on Sub-parsec Scales

We report multi-frequency VLBI studies of the sub-parsec scale structure of the two-sided jet in the nearby radio galaxy NGC 4261. Our analyses include new observations using the Source Frequency Phase Referencing technique with the Very Long Baseline Array at 44 and 88 GHz, as well as archival data at 15 and 43 GHz. Our results show an extended double-sided structure at 43/44 GHz and provide a clear image of the nuclear region at 88 GHz, showing a core size of $\sim$0.09 mas and a brightness temperature of $\sim1.3\times10^{9}$ K. Proper motions are measured for the first time in the two-sided jet, with apparent speeds ranging from $0.31\pm0.14\,c$ to $0.59\pm0.40\,c$ in the approaching jet and $0.32\pm0.14\,c$ in the receding jet. The jet-to-counter-jet brightness ratio allows us to constrain the viewing angle to between $\sim54^{\circ}$ and $84^{\circ}$ and the intrinsic speed to between $\sim0.30\,c$ and $0.55\,c$. We confirm the parabolic shape of the upstream jet on both sides of the central engine, with a power-law index of $0.56\pm0.07$. Notably, the jet collimation is found to be already completed at sub-parsec scales, with a transition location of about 0.61 pc, which is significantly smaller than the Bondi radius of 99.2 pc. This behavior can be interpreted as the initial confinement of the jet by external pressure from either the geometrically thick, optically thin advection-dominated accretion flows (ADAF) or the disk wind launched from it. Alternatively, the shape transition may also be explained by the internal flow transition from a magnetically dominated to a particle-dominated regime.Comment: 9 pages, 5 figures, 2 table

MFV approach to robust estimate of neutron lifetime

Aiming at evaluating the lifetime of the neutron, we introduce a novel statistical method to analyse the updated compilation of precise measurements including the 2022 dataset of Particle Data Group (PDG). Based on the minimization for the information loss principle, unlike the median statistics method, we apply the most frequent value (MFV) procedure to estimate the neutron lifetime, irrespective of the Gaussian or non-Gaussian distributions. Providing a more robust way, the calculated result of the MFV is $\tau_n=881.16^{+2.25}_{-2.35}$ s with statistical bootstrap errors, while the result of median statistics is $\tau_n=881.5^{+5.5}_{-3}$ s according to the binomial distribution. Using the different central estimates, we also construct the error distributions of neutron lifetime measurements and find the non-Gaussianity, which is still meaningful

Pyrolysis gas as a carbon source for biogas production via anaerobic digestion

Carbon is an important resource for anaerobes to enhance biogas production. In this study, the possibility of using simulated pyrolysis gas (SPG) as a carbon source for biogas production was investigated. The effects of stirring speed (SS), gas holding time (GHT), and H2 addition on biomethanation of SPG were evaluated. The diversity and structure of microbial communities were also analyzed under an illumina MiSeq platform. Results indicated that at a GHT of 14 h and an SS at 400 rpm, SPG with up to 64.7% CH4could be bio-upgraded to biogas. Gas–liquid mass transfer is the limitation for SPG biomethanation. For the first time, it has been noticed that the addition of H2 can bioupgrade SPG to high quality biogas (with 91.1% CH4). Methanobacterium was considered as a key factor in all reactors. This study provides an idea and alternative way to convert lignocellulosic biomass and solid organic waste into energy (e.g., pyrolysis was used as a pretreatment to produce pyrolysis gas from biomass, and then, pyrolysis gas was bioupgraded to higher quality biogas via anaerobic digestion)

Cluster-induced aggregation in polyurethane derivatives with multicolour emission and ultra-long organic room temperature phosphorescence

Non-conjugated luminescent polymers (NCLPs) have the advantages of simple synthesis, optical tunability, and excellent processability. However, the underlying luminous mechanism in NCLPs remains obscure and it is a considerable challenge to obtain NCLPs with ultra-long phosphorescence lifetime and multicolour emission simultaneously. In this article, linear polyurethane derivatives (PUs) with cluster-induced aggregation, multicolour luminescence and ultra-long phosphorescence have been prepared by simply adjusting the reaction temperature and the reaction time. DFT calculations and molecular dynamics simulations provide elaborate microstructural information on the PUs. With the synergistic effect of abundant hydrogen bonding interactions, through-space dative bonds, short interatomic contacts and oxygen clusters various luminous clusters are formed. The energy level splitting caused by clusters with different extents of spatial conjugation endows the NCLPs with multicolour clusteroluminescence, promotes intersystem crossing (ISC), and stabilises the triplet excited state, and finally an ultra-long room temperature phosphorescence (RTP) lifetime of 0.45 s is attained. Experimental encryption/decryption models validate the potential of the PUs in information security. The results have important implications for understanding the intrinsic mechanism of unconventional luminescence in the absence of any traditional conjugative units or heavy atom effects, and they provide a new horizon for the strategic design of multicolour luminescence and ultra-long phosphorescence in NCLPs for a range of practical applications