合成气直接合成二甲醚的动态建模

在红外干扰弹自身特性研究领域中,与其相对静态的辐射特性本文根据原子守恒方程、反应动力学方程及能量衡算方程对合成气直接合成二甲醚进行动态建模,将模型计算值与文献值进行比较,证明通过该方法建立的模型可以客观反映合成气直接合成二甲醚的基本特征。

Non-uniform thermal behavior of single-layer spherical reticulated shell structures considering time-variant environmental factors: analysis and design

Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.

On challenges of AI to cognitive security and safety

Recent advances in deep learning have led to disruptive breakthroughs in artificial intelligence(AI),fueling the jump in ChatGPT-like large language models(LLMs).As with any emerging technology,it is a two-sided coin,bringing not only vast social impacts but also significant security concerns,especially in the socio-cognitive domain.Against this back-ground,this work starts with an inherent mechanism analysis of cognitive domain games,from which it proceeds to explore the security concerns facing the cognitive domain as well as to analyze the formation mechanisms of a cognitive immune system.Finally,inspired by behavioral mimicry in biology,this work will elaborate on new approaches to cognitive security from three aspects:Mimicry Computing,Mimicry Defense,and Mimicry Intelligence.

Neuropilin-1^(high) monocytes protect against neonatal inflammation

Neonates are susceptible to inflammatory disorders such as necrotizing enterocolitis(NEC)due to their immature immune system.The timely appearance of regulatory immune cells in early life contributes to the control of inflammation in neonates,yet the underlying mechanisms of which remain poorly understood.In this study,we identified a subset of neonatal monocytes characterized by high levels of neuropilin-1(Nrp1),termed Nrp1^(high) monocytes.Compared with their Nrp1low counterparts,Nrp1^(high) monocytes displayed potent immunosuppressive activity.Nrp1 deficiency in myeloid cells aggravated the severity of NEC,whereas adoptive transfer of Nrp1^(high) monocytes led to remission of NEC.Mechanistic studies showed that Nrp1,by binding to its ligand Sema4a,induced intracellular p38-MAPK/mTOR signaling and activated the transcription factor KLF4.KLF4 transactivated Nos2 and enhanced the production of nitric oxide(NO),a key mediator of immunosuppression in monocytes.These findings reveal an important immunosuppressive axis in neonatal monocytes and provide a potential therapeutic strategy for treating inflammatory disorders in neonates.

A LuxR family transcriptional regulator AniF promotes the production of anisomycin and its derivatives in Streptomyces hygrospinosus var.beijingensis

The protein synthesis inhibitor anisomycin features a unique benzylpyrrolidine system and exhibits potent selective activity against pathogenic protozoa and fungi.It is one of the important effective components in Agricultural Antibiotic120,which has been widely used as naturally-originated agents for treatment of crop decay in China.The chemical synthesis of anisomycin has recently been reported,but the complex process with low productivity made the biosynthesis still to be a vital mainstay in efforts.The biosynthetic gene cluster(BGC)of anisomycin in Streptomyces hygrospinosus var.beijingensis has been identified in our previous work,while poor understanding of the regulatory mechanism limited the yield enhancement via regulation engineering of S.hygrospinosus var.beijingensis.In this study here,we characterized AniF as an indispensable LuxR family transcriptional regulator for the activation of anisomycin biosynthesis.The genetic manipulations of aniF and the real-time quantitative PCR(RT-qPCR)revealed that it positively regulated the transcription of the anisomycin BGC.Moreover,the overexpression of aniF contributed to the improvement of the production of anisomycin and its derivatives.Dissection of the mechanism underlying the function of AniF revealed that it directly activated the transcription of the genes aniR-G involved in anisomycin biosynthesis.Especially,one AniF-binding site in the promoter region of aniR was identified by DNase I footprinting assay and an inverted repeat sequence(5′-GGGC-3′)composed of two 4-nt half sites in the protected region was found.Taken together,our systematic study confirmed the positive regulatory role of AniF and might facilitate the future construction of engineering strains with high productivity of anisomycin and its derivatives.

Cytotoxic polyacetylenes isolated from the roots and rhizomes of Notopterygium incisum

Phytochemical investigation on the roots and rhizomes of Notopterygium incisum led to the isolation of a new polyacetylene, notopolyenol A (1), along with thirteen known analogues (2-14). Their structures were elucidated by extensive analyses of NMR and HRMS data, and the absolute configuration of 1 was unambiguously determined as 3 R by comparison of its retention time and ECD curve with those of synthetic enantiomers (-)-1 and (+)-1, whose absolute configurations were established by using the modified Mosher's method. Subsequent activity screening revealed that (3 S)-1 exhibited the most significant cytotoxicity against MCF-7, H1299, and HepG2 cancer cells with IC_(50) values of 1.3 μmol/L,0.6μmol/L and 1.4μmol/L, respectively.