Hyperchaos,quasi-period and coexisting behaviors in second-order-memristor-based jerk circuit

The European Physical Journal Special Topics - This paper generalizes a second-order-memristor-based jerk circuit, which is achieved by substituting the first-order memristor contained diode-bridge...     

改进的五阶WENO-Z+格式

WENO-ZWENO-Z$+\!$格式的性能提升依赖于新增项的作用,该项的作用是在WENO-Z格式的基础上进一步增大欠光滑子模板上的权重. 系数$\lambda$被设置用来调控该项的作用, 以避免负耗散. 本文指出了WENO-Z$+\!$格式的缺陷,其所采用$\lambda $的取值方式既不能充分发挥格式的潜力, 也未完全消除负耗散;提出$\lambda $的值应随当地流场数据变化,方能充分发挥新增项在降低数值耗散、提高分辨率上的潜力. 基于此,本文重新设计了$\lambda $的计算公式,该公式能自适应地调控新增项的作用: 只在欠光滑子模板上的权重容易过度增大的地方削弱该项的作用,以避免负耗散; 在其他地方则充分发挥新增项的作用,最大限度增大欠光滑子模板上的权重, 提高格式的分辨率.将使用该系数公式的新格式命名为WENO-Z++, 并对其数值性能进行了系统的研究.理论分析表明, 新格式在间断处具有基本无振荡(essentially non-oscillatory,ENO)特性和更低的数值耗散. 对近似色散关系(approximate dispersion relation,ADR)的研究表明,新格式有效地避免了因过度增大欠光滑子模板上的权重而带来的负耗散,其频谱特性也得到了显著提升.本文还推导了使新格式在极值点处也能保持最优阶的精度的参数设置.一系列求解Euler方程的数值试验表明,新格式的激波捕捉能力和对复杂流场结构的分辨率都显著优于原WENO-Z$+\!$格式.}     

Computer Simulation Study on Adsorption and Conformation of Polymer Chains Driven by External Force

In this work, Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface. The critical adsorption temperature T_c decreases linearly with increasing F,indicating that the driving force suppresses the adsorption of polymer. The conformation of polymer is also affected by the driving force.However, the effect of F is dependent on the competition between the driving force and temperature. Under strong force or at low temperature,the polymer is stretched along the direction of the force, while under weak force or at high temperature, the polymer is not stretched. When the force is comparable to the temperature, the polymer may be stretched perpendicular to the driving force, and below T_c, we observe conformational transitions from parallel to perpendicular and again to parallel by decreasing the temperature. We found that the perpendicular stretched conformation leads the polymer chain to synchronously move along the direction of the driving force. Moreover, the conformational transitions are attributed to the competition and cooperation between the driving force and the temperature.     

Acceptorless dehydrogenative synthesis of primary amides from alcohols and ammonia

The highly desirable synthesis of the widely-used primary amides directly from alcohols and ammonia via acceptorless dehydrogenative coupling represents a clean, atom-economical, sustainable process. Nevertheless, such a reaction has not been previously reported, and the existing catalytic systems instead generate other N-containing products, e.g., amines, imines and nitriles. Herein, we demonstrate an efficient and selective ruthenium-catalyzed synthesis of primary amides from alcohols and ammonia gas, accompanied by H₂ liberation. Various aliphatic and aromatic primary amides were synthesized in high yields, with no observable N-containing byproducts. The selectivity of this system toward primary amide formation is rationalized through density functional theory (DFT) calculations, which show that dehydrogenation of the hemiaminal intermediate into primary amide is energetically favored over its dehydration into imine.

An efficient and selective synthesis of primary amides from alcohols and ammonia, with H₂ evolution, has been achieved by an unprecedented acceptorless dehydrogenative process catalyzed by a pyridine-based PNN–ruthenium pincer complex.     

PBDEs研究的最新进展

多澳联苯醚(PBDEs)是一类环境中广泛存在的全球性有机污染物.由于其具有环境持久性、远距离传输、生物可累积性及对生物和人体具有毒害效应等特性,对其环境问题的研究已成为当前环境科学的一大热点.本文对最近几年来环境中PBDEs研究的进展进行综述,对多溴联苯醚在环境及生物体中的分布、时间趋势、人体暴露及途径、环境中的降解和生物代谢以及生物累积与生物放大方面的研究进行了总结,对目前存在问题及进一步的研究方向进行了讨论和展望.     

双β-二酮配体配位性的理论研究

基于自洽反应场(SCRF)中的极化连续介质模型(PCM), 采用密度泛函理论B3LYP/6-31G**计算了以二硫醚和芳环为桥基的两类双β-二酮配体的空间构型和电子结构, 结合其配合物晶体结构数据, 研究配体分子电子结构与配位性的关联性. 结果表明, 配体分子的几何构型、前线轨道、偶极矩和电荷布居, 与配合物构型、活性配位原子和配位形式(单核或多核、分子内或分子间)之间的关联性与一致性十分有意义. 配体的理论计算研究可以在一定层次上为配合物几何结构特征和配位特性提供合理的分析与预测.     

Novel facile detection of persistent organic pollutants using highly sensitive gas sensor

Persistent organic pollutants (POPs) are greatly noxious chemicals in environment, and they can cumulate in organisms and transfer between different species. Therefore, it is significant to detect POPs for both environmental evaluation and further treatment. However, developing facile approach for the detection of POPs still remains a challenge so far. In this paper, we report an innovative method for facile detection of POPs using gas sensor for the first time. Porous SnO₂ nanostructures with a special tri-walled structure prepared via hydrothermal route and annealing process, were employed as gas-sensing materials. Through gas measurements, it was revealed that the as-fabricated gas sensor exhibited highly sensitive performance towards target POPs, including methoxychlor, mirex, p,p′-DDT, and aldrin. Moreover, we found that target POPs were distinguishable by extracting characteristics in kinetic curves of gas adsorption-desorption. As the presented detecting approach is facile without the requirements of complex operations, expensive and bulky instruments, it is expected that it would be developed as a promising method for the detection of POPs, and thereby showing its significance for environmental monitoring.     

In situ chemical fabrication of polyaniline/multi-walled carbon nanotubes composites as supports of Pt for methanol electrooxidation

Science China Chemistry - In this study, platinum (Pt)-polyaniline(PANI)/MWNTs catalysts were synthesized by two sequential reactions. First, core-shell structural PANI/MWNTs composites were...     

Controlled formation of novel supramolecular microbelts or microprisms from aniline and H2PdCl4 driven by coordination and π–π interactions

In this communication, I report the formation of novel supramolecular one-dimensional (1D) structures including microbelts and microprisms by a direct mix of aniline and H₂PdCl₄ aqueous solutions at room temperature. As-formed supramolecular structures were characterised by scanning electron microscopy, X-ray photoelectron spectra and X-ray diffraction techniques. Both coordination and π–π interactions are expected to be responsible for these 1D microstructures. It suggests that the molar ratio of the reactants is crucial to the formation of such 1D structures.     

Cytosolic escape of mitochondrial DNA triggers cGAS-STING-NLRP3 axis-dependent nucleus pulposus cell pyroptosis

Low back pain (LBP) is a major musculoskeletal disorder and the socioeconomic problem with a high prevalence that mainly involves intervertebral disc (IVD) degeneration, characterized by progressive nucleus pulposus (NP) cell death and the development of an inflammatory microenvironment in NP tissue. Excessively accumulated cytosolic DNA acts as a damage-associated molecular pattern (DAMP) that is monitored by the cGAS-STING axis to trigger the immune response in many degenerative diseases. NLRP3 inflammasome-dependent pyroptosis is a type of inflammatory programmed death that promotes a chronic inflammatory response and tissue degeneration. However, the relationship between the cGAS-STING axis and NLRP3 inflammasome-induced pyroptosis in the pathogenesis of IVD degeneration remains unclear. Here, we used magnetic resonance imaging (MRI) and histopathology to demonstrate that cGAS, STING, and NLRP3 are associated with the degree of IVD degeneration. Oxidative stress induced cGAS-STING axis activation and NLRP3 inflammasome-mediated pyroptosis in a STING-dependent manner in human NP cells. Interestingly, the canonical morphological and functional characteristics of mitochondrial permeability transition pore (mPTP) opening with the cytosolic escape of mitochondrial DNA (mtDNA) were observed in human NP cells under oxidative stress. Furthermore, the administration of a specific pharmacological inhibitor of mPTP and self-mtDNA cytosolic leakage effectively reduced NLRP3 inflammasome-mediated pyroptotic NP cell death and microenvironmental inflammation in vitro and degenerative progression in a rat disc needle puncture model. Collectively, these data highlight the critical roles of the cGAS-STING-NLRP3 axis and pyroptosis in the progression of IVD degeneration and provide promising therapeutic approaches for discogenic LBP.Subject terms: Cell death, Diseases