1. The aquatic environments of inland rivers are relatively independent and highly heterogeneous. As the second largest inland river in China, the water resources of the Heihe River are intensively exploited in its middle and downstream sections, while the responses of water quality and the community assembly mechanisms (deterministic or stochastic processes) of bacterioplankton to these intensively anthropogenic disturbances remain poorly characterized. In this study, we integrated niche-neutrality dynamic balancing to investigate the dispersal dynamics of bacterioplankton communities in the Heihe River along gradients of human activity intensity. 2. We found that the upstream landscape of the Heihe River has greater landscape connectivity and better water quality, whereas the downstream landscape is more fragmented and has poorer water quality. The alpha-diversity of bacterial communities decreased significantly from upstream to downstream. Meanwhile, community assembly in the plateau meadow (PM) region was dominated by stochastic processes driven by dispersal limitation, whereas deterministic processes dominated by homogeneous selection drove the assembly and turnover of bacteria in other regions. 3. These results indicated that agricultural disturbances could lead to the deterioration of water quality downstream and affect river microbial community assembly. To protect the microbial diversity of the watershed, therefore, more attention should be paid to landscape configuration parameters in the agricultural oasis (AO) region. 4. Our findings contribute to a deeper understanding of the microbial ecology in inland rivers under different landscape patterns and provide valuable guidance for the protection of inland rivers and the development of landscape ecology in the regions surrounding rivers.
Modifying phosphorus-based flame retardants to balance their flame-retardant and mechanical properties has become an emerging research trend in the field of polylactic acid (PLA). In this study, an attapulgite-based phosphorus-nitrogen-silicon hybrid flame retardant (ATP@PSi-NH2) was designed and synthesized by coating a phosphorus-nitrogen-silicon hybrid flame retardant (PSi-NH2) onto the surface of attapulgite (ATP) using the bridging agent KH560. The effects of ATP-KH560, PSi-NH2, and ATP@PSi-NH2 flame retardants on the thermal stability, flame retardancy, and mechanical properties of PLA composites were compared. The incorporation of ATP@PSi-NH2 significantly enhanced the balance between flame retardancy and mechanical performance of the PLA composites. The PLA composite containing 7.5 wt.% ATP@PSi-NH2 achieved a UL-94V-0 rating, with the limiting oxygen index (LOI) increasing to 27.6%. At the same phosphorus content, the total smoke production (TSP) and total smoke release (TSR) of PLA/10ATP@PSi-NH2 were reduced by 38.6% and 39.3%, respectively, compared to the PLA/5PSi-NH2 composite, demonstrating the smoke-suppressing effect of ATP. Furthermore, due to the enhanced interfacial compatibility of ATP@PSi-NH2 within the PLA matrix and the nail-pull effect of ATP, the PLA/ATP@PSi-NH2 composite exhibited superior mechanical properties. This study successfully combines the benefits of phosphorus-based and nano-flame retardants to improve the flame-retardant performance of PLA, providing an effective approach for the development of multifunctional flame retardants.
To explore the responses of soil microbial diversity and community structure to elevation gradient (2,700—3,300 m) in Qinghai spruce forest on the northern slope of Qilian Mountain, and to reveal the vertical distribution and driving mechanism of microbial community in climate change sensitive areas. Soil profile samples (0—60 cm depth) were collected at an altitude of 2,700—3,300 m. Bacterial (16S rRNA gene) and fungal (ITS region) community structure was analyzed by Illumina sequencing technique; soil physical and chemical properties such as bulk density (BD), pH, soil organic carbon (SOC), total nitrogen (TN), alkaline nitrogen (AHN), microbial biomass carbon and nitrogen (MBC, MBN), as well as slope gradient were simultaneously measured. 1) Significant altitudinal differences (P < 0.05) were observed in fungal and bacterial α-diversity. The bacterial community reached its peak α-diversity at 3,300 m. The fungal community also exhibited its highest richness (as measured by Chao1 and ACE indices) at 3,300 m. 2) Abundance of dominant bacterial phyla (Pseudomonadota, Actinomycetota, Gemmatimonadota) was significantly affected by altitude (P < 0.05): Pseudomonadota abundance at 3,300 m was significantly higher than that at 2,900 m and 2,800 m; Actinomycetota and Gemmatimonadota were more abundant at 2,700 m than at 3,300 m (P < 0.05). The dominant phylum of fungal (Basidiomycota, Ascomycota, Mortierellomycota) had no significant altitude difference (P > 0.05). 3) Variation of bacterial communities was driven by pH, MBC, TN, and TP. Fungal community was regulated by slope, pH, BD, TN, TK, MBC, and SOC. 4) Bacterial networks were most complex at 2,850 m and simplest at 3,200 m. Fungal networks were consistently simpler than bacterial networks. Altitude gradient significantly impacted the microbial community structure by changing soil physical and chemical properties. Bacterial communities exhibited greater sensitivity to elevation changes than fungal, manifested in diversity peak shifts, community structure changes driven by multiple factors, and more complex network structures.
The cross-section of the reaction 78Kr(n,2n)77Kr was measured at five neutron energies of 13.59 f 0.12, 13.86 f 0.15, 14.13 f 0.16, 14.70 f 0.13, and 14.94 f 0.02 MeV using the activation method. The target sample was pure, high-pressure natural Kr gas. Neutron irradiation was carried out on the K-400 type neutron generator at the China Academy of Engineering Physics (CAEP). Quasi-single energy neutrons were produced by the reaction 3H(d,n)4He. The fluctuation of neutron yield was detected using the associated alpha-particle method. The neutron energy and its uncertainty were calculated using the Q-value equation, taking into account the sample's position and the solid angle it occupied. The standard 93Nb(n,2n)92mNb reaction was used to monitor the neutrons injected into the sample. Samples's self-absorption of characteristic gamma-rays, geometric position, and solid angle during irradiation were corrected. The cross-section values of the reaction 78Kr(n,2n)77Kr from threshold energy to 20 MeV were calculated using the program Talys-2.0. Except for the six-level density variations, default parameters were used throughout the calculation. The measured results were compared and discussed in relation to the reported experimental values, theoretical values, evaluation values, and systematic results. The current experimental results can help to verify nuclear theory, evaluate nuclear reaction cross-section databases, and are applicable to nuclear technology.
Neuromorphic circuits that simulate the sleep cycle serve as a critical bridge between neuroscience and hardware implementation. To address the limitations of conventional circuits, which are often complex and lack mechanisms for biological plasticity and memory, this paper presents two highly compact memristor-transistor hybrid neural network circuits designed to simulate transitions between different sleep stages. The core innovations of this design are: 1) utilizing the non-volatile memory property of individual memristors to directly implement the retention of neuronal activation states in hardware, thereby simulating the persistence of sleep stages; and 2) employing a specific memristor connection topology to accurately simulate the indirect and direct inhibitory functions of gamma-aminobutyric acid (GABA)-ergic neurons in the rostromedial tegmental nucleus (RMTg) region on neurons in the laterodorsal tegmentum (LDT) and laterodorsal hypothalamus (LH) regions, using a minimal number of components. Based on this design, corresponding circuits are constructed and simulated using PSPICE. The results demonstrate that this memristive neural network can successfully simulate state transitions between wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep by modelling the activation of GABAergic neurons in the RMTg and their subsequent inhibitory effects in the LDT and LH regions. The designed circuits exhibit a high degree of functional alignment with the target biological neural networks. Furthermore, simulation analysis confirms that the circuit can not only represent normal sleep architecture but also, by adjusting the initial states of key memristors, quantitatively replicate and differentiate the sleep structure fragments between healthy elderly individuals and young adults.
