氧扩散与表面反应在VO_(x)-Ce_(1-x)Zr_(x)O_(2)催化丙烷脱氢反应中的影响

丙烯是一种重要的化工原料,近年来市场需求逐年上升.丙烷直接脱氢(PDH)生产丙烯技术虽然已实现工业化应用,但其存在反应热力学不利、催化剂成本高及使用有毒铬系催化剂等问题.丙烷氧化脱氢(ODH)由于过度氧化严重和存在操作风险等问题阻碍了其实际应用.化学链丙烷脱氢(CL-ODH)技术采用低成本且环境友好的可还原金属氧化物作为氧载体(氧化还原催化剂),并利用更高效的晶格氧作为氧化剂替代传统ODH过程中的氧气,在改善丙烷脱氢反应热力学限制的同时抑制了烷烃分子的过度氧化.氧化还原催化剂在该过程中发挥着重要的作用,其设计得到了研究者们的广泛关注.目前,铈锆储氧材料担载的钒催化剂由于在烷烃选择性氧化以及储氧能力方面的优势,在CL-ODH领域展示出良好的应用前景.然而,由于体相氧传输和表面反应共同决定氧化还原催化剂的性能,因此深入探究两者在反应过程中的作用机制对于高性能催化剂的开发至关重要.本文构建了结构明确的VO_(x)-Ce_(1-x)Zr_(x)O_(2)氧化还原催化剂并应用于CL-ODH反应,通过引入Zr调控催化剂的表面和体相性质,进而对其表面反应活性和体相供氧能力进行调节.其中,VO_(x)-Ce_(0.3)Zr_(0.7)O_(2)样品表现出相对较高的丙烯生成速率(5.07mmol·g_(cat)^(-1)h^(-1)).H_(2)程序升温还原和C_(3)H_(8)程序升温还原结果表明,Zr的引入增强了氧化还原催化剂的低温体相供氧能力以及表面本征活性,因此增加了活性氧物种的数量并促进了表面丙烷分子的活化.动力学实验结果表明,VO_(x)-Ce_(1-x)Zr_(x)O_(2)氧化还原催化剂上的脱氢反应遵循一级反应动力学规律,说明表面反应为催化剂还原过程的速控步骤,同时,在快速的体相氧扩散作用下,催化剂内部的氧物种呈现均匀分布的特点.进一步分析表面反应过程和体相氧传输对于氧化还原催化剂表面氧物种覆盖度的影响,建立了描述VO_(x)-Ce_(1-x)Zr_(x)O_(2)在脱氢阶段反应模型的动力学方程.其中,吸附态丙烷分子的C-H键断裂是表面反应的速控步骤,Zr的引入可以有效降低该步骤的活化能,进而提高了氧化还原催化剂在给定表面氧物种覆盖度时对应的表面反应速率.同时,随着反应的进行,为了消除VO_(x-)Ce_(1-x)Zr_(x)O_(2)内部产生的氧浓度梯度,氧扩散起到了将表面反应产生的氧空位快速转移到体相的作用,从而有效地保持了反应过程中表面活性氧的覆盖度.并且随着Zr的引入,Ce_(1-x)Zr_(x)O_(2)的储氧能力得以增强,可容纳更多来自表面的氧空位,从而使表面氧化活性保持更长时间.此外,通过拉曼光谱、X射线光电子能谱和原位漫反射红外傅立叶变换光谱等多种原位表征技术对上述反应模型进行了验证.综上,本文为V基氧化还原催化剂应用于CL-ODH反应过程中氧扩散和表面反应的作用提供了更深入的认识,并为高性能氧化还原催化剂的设计提供了理论参考.

Characteristics of glucose and lipid metabolism and the interaction between gut microbiota and colonic mucosal immunity in pigs during cold exposure

Background Cold regions have long autumn and winter seasons and low ambient temperatures.When pigs are unable to adjust to the cold,oxidative damage and inflammation may develop.However,the differences between cold and non-cold adaptation regarding glucose and lipid metabolism,gut microbiota and colonic mucosal immunological features in pigs are unknown.This study revealed the glucose and lipid metabolic responses and the dual role of gut microbiota in pigs during cold and non-cold adaptation.Moreover,the regulatory effects of dietary glucose supplements on glucose and lipid metabolism and the colonic mucosal barrier were evaluated in cold-exposed pigs.Results Cold and non-cold-adapted models were established by Min and Yorkshire pigs.Our results exhibited that cold exposure induced glucose overconsumption in non-cold-adapted pig models(Yorkshire pigs),decreasing plasma glucose concentrations.In this case,cold exposure enhanced the ATGL and CPT-1αexpression to promote liver lipolysis and fatty acid oxidation.Meanwhile,the two probiotics(Collinsella and Bifidobacterium)depletion and the enrichment of two pathogens(Sutterella and Escherichia-Shigella)in colonic microbiota are not conducive to colonic mucosal immunity.However,glucagon-mediated hepatic glycogenolysis in cold-adapted pig models(Min pigs)maintained the stability of glucose homeostasis during cold exposure.It contributed to the gut microbiota(including the enrichment of the Rikenellaceae RC9 gut group,[Eubacterium]coprostanoligenes group and WCHB1-41)that favored cold-adapted metabolism.Conclusions The results of both models indicate that the gut microbiota during cold adaptation contributes to the protection of the colonic mucosa.During non-cold adaptation,cold-induced glucose overconsumption promotes thermogenesis through lipolysis,but interferes with the gut microbiome and colonic mucosal immunity.Furthermore,glucagon-mediated hepatic glycogenolysis contributes to glucose homeostasis during cold exposure.

A New Sensitivity Analysis Approach Using Conditional Nonlinear Optimal Perturbations and Its Preliminary Application

Simulations and predictions using numerical models show considerable uncertainties,and parameter uncertainty is one of the most important sources.It is impractical to improve the simulation and prediction abilities by reducing the uncertainties of all parameters.Therefore,identifying the sensitive parameters or parameter combinations is crucial.This study proposes a novel approach:conditional nonlinear optimal perturbations sensitivity analysis(CNOPSA)method.The CNOPSA method fully considers the nonlinear synergistic effects of parameters in the whole parameter space and quantitatively estimates the maximum effects of parameter uncertainties,prone to extreme events.Results of the analytical g-function test indicate that the CNOPSA method can effectively identify the sensitivity of variables.Numerical results of the theoretical five-variable grassland ecosystem model show that the maximum influence of the simulated wilted biomass caused by parameter uncertainty can be estimated and computed by employing the CNOPSA method.The identified sensitive parameters can easily change the simulation or prediction of the wilted biomass,which affects the transformation of the grassland state in the grassland ecosystem.The variance-based approach may underestimate the parameter sensitivity because it only considers the influence of limited parameter samples from a statistical view.This study verifies that the CNOPSA method is effective and feasible for exploring the important and sensitive physical parameters or parameter combinations in numerical models.

Synthesis and Characterization of a Silica-Based Drug Delivery System for Spinal Cord Injury Therapy

Acute inflammation is a central component in the progression of spinal cord injury(SCI).Anti-inflammatory drugs used in the clinic are often administered systemically at high doses,which can paradoxically increase inflammation and result in drug toxicity.A cluster-like mesoporous silica/arctigenin/CAQK composite(MSN-FC@ARCG)drug delivery system was designed to avoid systemic side effects of high-dose therapy by enabling site-specific drug delivery to the spinal cord.In this nanosystem,mesoporous silica was modified with the FITC fluorescent molecule and CAQK peptides that target brain injury and SCI sites.The size of the nanocarrier was kept at approximately 100 nm to enable penetration of the blood–brain barrier.Arctigenin,a Chinese herbal medicine,was loaded into the nanosystem to reduce inflammation.The in vivo results showed that MSN-FC@ARC-G could attenuate inflammation at the injury site.Behavior and morphology experiments suggested that MSN-FC@ARC-G could diminish local microenvironment damage,especially reducing the expression of interleukin-17(IL-17) and IL-17-related inflammatory factors,inhibiting the activation of astrocytes,thus protecting neurons and accelerating the recovery of SCI.Our study demonstrated that this novel,silica-based drug delivery system has promising potential for clinical application in SCI therapy.

Analysis on Tourism Economic Spatial Relation of Liaoning Central City Group

Through the calculation and analysis of the tourism economic spatial relation,it found that Liaoning central urban agglomeration tourism economic spatial relation has many problems,such as the central city is insufficient,and the low degree of spatial relations. Therefore,this article puts forward the countermeasures,which can provide theoretical and practical reference for Liaoning central urban agglomeration tourism industry layout.

Research on the Development and Evolution Mechanism of Chongqing Rural Tourism Activities

In this paper, we conduct research on the development and evolution mechanism of Chongqing rural tourism activities. Rural tourism industry cluster development is the important direction is to promote and enhance the rural tourism the important measures to get long-term vitality. To upgrade the development of rural tourism to the height of the industrial cluster will make the rural tourism development onto a new level. In the future, we will combine more related literature review to polish and modify the proposed methodology which will be meaningful.

“人的解放辩证法”与马克思主义政治哲学的现代阐释——基于中国情境的思考

“卢森堡-诺伊曼问题”构成了马克思主义政治哲学现代阐释的基本背景和核心课题。“人的解放辩证法”蕴含着情境主义-普遍主义的政治/法律发展逻辑:一个社会的政治/法律秩序应朝着有利于“政治解放”和“人的解放”的方向发展,但是其具体的制度和实践模式具有受制于具体社会历史条件的特殊性。国家理论、民主法治理论、正义理论和国际政治理论,构成了遵循“人的解放辩证法”推进马克思主义政治哲学现代阐释的四大基础课题。马克思主义政治哲学的现代阐释,旨在充分挖掘作为“学说”的马克思主义的普遍主义色彩和认知性内涵,使其充分发挥面对西方的“对话-抗辩”功能、面对现实的“阐释-范导”功能和面对历史的“阐释-反思”功能。以中国现代性、中国式现代化为思想根据推进马克思主义政治哲学的现代阐释,会迈向一种“马克思主义的阐释政治哲学”。

Glucose supplementation improves intestinal amino acid transport and muscle amino acid pool in pigs during chronic cold exposure

Mammals in northern regions chronically suffer from low temperatures during autumn-winter seasons.The aim of this study was to investigate the response of intestinal amino acid transport and the amino acid pool in muscle to chronic cold exposure via Min pig models(cold adaptation)and Yorkshire pig models(non-cold adaptation).Furthermore,this study explored the beneficial effects of glucose supplementation on small intestinal amino acid transport and amino acid pool in muscle of cold-exposed Yorkshire pigs.Min pigs(Exp.1)and Yorkshire pigs(Exp.2)were divided into a control group(17℃,n=6)and chronic cold exposure group(7℃,n=6),respectively.Twelve Yorkshire pigs(Exp.3)were divided into a cold control group and cold glucose supplementation group(8℃).The results showed that chronic cold exposure inhibited peptide transporter protein 1(PepT1)and excitatory amino acid transporter 3(EAAT3)expression in ileal mucosa and cationic amino acid transporter-1(CAT-1)in the jejunal mucosa of Yorkshire pigs(P<0.05).In contrast,CAT-1,PepT1 and EAAT3 expression was enhanced in the duodenal mucosa of Min pigs(P<0.05).Branched amino acids(BCAA)in the muscle of Yorkshire pigs were consumed by chronic cold exposure,accompanied by increased muscle RING-finger protein-1(MuRF1)and muscle atrophy F-box(atrogin-1)expression(P<0.05).More importantly,reduced concentrations of dystrophin were detected in the muscle of Yorkshire pigs(P<0.05).However,glycine concentration in the muscle of Min pigs was raised(P<0.05).In the absence of interaction between chronic cold exposure and glucose supplementation,glucose supplementation improved CAT-1 expression in the jejunal mucosa and PepT1 expression in the ileal mucosa of cold-exposed Yorkshire pigs(P<0.05).It also improved BCAA and inhibited MuRF1 and atrogin-1 expression in muscle(P<0.05).Moreover,dystrophin concentration was improved by glucose supplementation(P<0.05).In summary,chronic cold exposure inhibits amino acid absorption in the small intestine,depletes BCAA and promotes protein degradation in muscle.Glucose supplementation ameliorates the negative effects of chronic cold exposure on amino acid transport and the amino acid pool in muscle.

On the boundedness of running-in attractors based on recurrence plot and recurrence qualification analysis

A feature parameter was proposed to quantitatively explore the boundedness of running-in attractors;its variation throughout the friction process was also investigated. The enclosing radius R was built with recurrence plots(RPs) and recurrence qualification analysis(RQA) by using the time delay embedding and phase space reconstruction. Additionally, the typology of RPs and the recurrence rate(RR) were investigated to verify the applicability of R in characterizing the friction process. Results showed that R is larger at the beginning, but exhibits a downward trend in the running-in friction process;R becomes smooth and trends to small steady values during the steady-state friction period, and finally shows an upward trend until failure occurs. The evolution of R, which corresponded with the typology of RPs and RR during friction process, can be used to quantitatively analyze the variation of the running-in attractors and friction state identifacation. Hence, R is a valid parameter, and the boundedness of running-in attractors can offer a new way for monitoring the friction state of tribological pairs.

A multi-criteria fusion feature selection algorithm for fault diagnosis of helicopter planetary gear train

Planetary gear train is a prominent component of helicopter transmission system and its health is of great significance for the flight safety of the helicopter.During health condition monitoring,the selection of a fault sensitive feature subset is meaningful for fault diagnosis of helicopter planetary gear train.According to actual situation,this paper proposed a multi-criteria fusion feature selection algorithm (MCFFSA) to identify an optimal feature subset from the highdimensional original feature space.In MCFFSA,a fault feature set of multiple domains,including time domain,frequency domain and wavelet domain,is first extracted from the raw vibration dataset.Four targeted criteria are then fused by multi-objective evolutionary algorithm based on decomposition (MOEA/D) to find Proto-efficient subsets,wherein two criteria for measuring diagnostic performance are assessed by sparse Bayesian extreme learning machine (SBELM).Further,Fmeasure is adopted to identify the optimal feature subset,which was employed for subsequent fault diagnosis.The effectiveness of MCFFSA is validated through six fault recognition datasets from a real helicopter transmission platform.The experimental results illustrate the superiority of combination of MOEA/D and SBELM in MCFFSA,and comparative analysis demonstrates that the optimal feature subset provided by MCFFSA can achieve a better diagnosis performance than other algorithms.

Chaotic characteristics and attractor evolution of friction noise during friction process

Friction experiments are conducted on a ring-on-disk tribometer, and friction noise produced during the friction process is extracted by a microphone. The phase trajectory and chaotic parameters of friction noise are obtained by phase-space reconstruction, and its attractor evolution is analyzed. The results indicate that the friction noise is chaotic because the largest Lyapunov exponent is positive. The phase trajectory of the friction noise follows a "convergence-stability-divergence" pattern during the friction process. The friction noise attractor begins forming in the running-in process, and the correlation dimension D increases gradually. In the stable process, the attractor remains steady, and D is stable. In the last step of the process, the attractor gradually disappears, and D decreases. The friction noise attractor is a chaotic attractor. Knowledge of the dynamic evolution of this attractor can help identify wear state changes from the running-in process to the steady and increasing friction processes.

Inhibition of MALT1 paracaspase activity improves lesion recovery following spinal cord injury

Spinal cord injury(SCI) is a devastating traumatic injury that causes persistent, severe motor and sensory dysfunction. Immune responses are involved in functional recovery after SCI. Mucosa-associated lymphoid tissue lymphoma translocation 1(MALT1) has been shown to regulate the survival and differentiation of immune cells and to play a critical role in many diseases, but its function in lesion recovery after SCI remains unclear. In this paper, we generated KI(knock in) mice with a point mutation(C472 G) in the active center of MALT1 and found that the KI mice exhibited improved functional recovery after SCI.Fewer macrophages were recruited to the injury site in KI mice and these macrophages differentiated into anti-inflammatory macrophages. Moreover, macrophages from KI mice exhibited reduced phosphorylation of p65, which in turn resulted in decreased SOCS3 expression and increased pSTAT6 levels.Similar results were obtained upon inhibition of MALT1 paracaspase with the small molecule inhibitor‘‘MI-2' or the more specific inhibitor ‘‘MLT-827'. In patients with SCI, peripheral blood mononuclear cells(PBMC) displayed increased MALT1 paracaspase. Human macrophages showed reduced proinflammatory and increased anti-inflammatory characteristics following the inhibition of MALT1 paracaspase. These findings suggest that inhibition of MALT1 paracaspase activity in the clinic may improve lesion recovery in subjects with SCI.

Nanostructured Catalysts toward Efficient Propane Dehydrogenation

CONSPECTUS:Propylene serves as one of the most significant compounds in the chemical industry.Propane dehydrogenation(PDH),an“on purpose”propylene production technology is developing.Pt-and CrOx-based catalysts are widely applied in commercialized PDH processes,and both exhibit high activity and propylene yields.However,as an intensively endothermic process,PDH requires operation at high temperatures(generally above 500°C),which restricts the C3H6 selectivity and catalyst structure stability on account of coking side reactions,particle sintering,and so forth.Nanostructured catalysts(NCs)based on metals and/or metal oxides with tunable geometric and electronic properties play significant roles because such features intrinsically influence the adsorption of propyl intermediates on the catalyst surface.However,thermodynamical metastability of these NCs results in grand challenges in their structure-controlled preparation.The regulation of material structure and reaction performance at the molecular and atomic levels has attracted extended attention over the past few years.This Account describes our recent advances in controllable regulation of metal and oxide NCs toward efficient propane dehydrogenation.As a structure-insensitive reaction,the dehydrogenation of propane can occur on an individual active site,while larger ensembles of active sites also induce structure-sensitive side reactions,leading to C−C cracking and coke deposition.This paper is aimed at delivering general fundamentals for rational design of NCs in PDH reactions.We start with the catalytic kinetics on the active sites regarding the adsorption of key propyl intermediates on the surface.In subsequent sections,we present the effective regulation strategies for metal and oxide NCs by promoter and support effects.Upon metal NCs,coke deposition and nanoparticles(NPs)sintering tend to occur,which can be suppressed with the increase of geometric separation and charge density of surface active sites by changing alloy compositions,ordered intermetallic alloys,single-atom catalysts,core−shell,and metal−oxide interface structures.Notably,the confinement approach of embedding active sites in zeolite frameworks significantly inhibits the sintering of metal NPs.As alternatives to metals,metal oxides exhibit lower cost but higher barriers of C−H activation and coking inclination.The C−H bond cleavage has been promoted by inducing intrinsic defect sites,such as oxygen vacancies,hydroxyls,and hydrides on the surface and heterogeneous doping in the bulk.Importantly,the structures of the submonolayer/monolayer triggered by spontaneous dispersion and confinement in mesoporous materials significantly improve the oxide activity and stability.All of these strategies have been essential for the efficient PDH reactions.Moreover,the challenges and perspectives are also discussed.It is hoped that the deliberate manipulation of nanostructured catalysts to regulate the reaction mechanism will hold the key to efficient alkane conversion.

The Introversive Political Meritocracy:A Political Possibility Beyond"The End of History"

The criticisms of the falsity of universal recognition carried| out by leftists, led by Karl Max, and the queries of its desirability proposed by rightists, represented by Friedrich Nietzsche, raise challenges to Francis Fukuyama’s theory of “the end of history” from two opposite directions. At present, Chinese-style political meritoc­racy based on the party state is a political form that combines these left-wing and right-wing challenges and has the potential to move beyond “the end of history”. However, whether it can truly surpass “the end of history” depends on whether it can form a desirable and stable alternative political form under modern condi­tions. To this end, Chinese-style political meritocracy must respond positively to the three challenges it faces under modern conditions: the tension between “debicheng- wei” (one’s virtue must have a matching position, 德必称位) and moral universal- ism, the corrosion of social justice from the hierarchical social structure caused by “weibichenglu” (one’s position must have a matching salary, 位必称禄), and the threat of social indoctrination to individual autonomy. The “introversive political meritocracy” jointly shaped by “advocating morals for the public,” “arete based on altruism,” and “introversive self-cultivation” is a desirable political form that can successfully respond to these three challenges.

“民主社会学”视角下国家与社会的相因相成——基于思想史重构的政治哲学分析

现代早期的市民社会,大致经历了从政治共同体到文化共同体的含义转变。在19世纪,由黑格尔和马克思率先理论化的市民社会是与经济社会耦合在一起的。20世纪以来,主要由于葛兰西和阿伦特的理论贡献,特别是哈贝马斯的辩证综合,市民社会开始具有自主的文化和政治内涵。后冷战时代,以南茜·弗雷泽与艾丽斯·M.杨为代表的学者开始聚焦于市民社会的社会基础,并系统阐发了国家与社会之间相互约束、互相依存的关系。基于“民主社会学”视角,良性的国家与社会关系是一种相因相成的关系:社会涵养国家的共识基础;国家滋育社会的功能环境。

Conceptualizing and Measuring Global Justice:Theories,Concepts,Principles and Indicators

The paper focuses on the conceptualization and measurement of global justice and discusses theories,concepts,evaluative principles,and methodologies related to the study of global justice.In this paper,we seek to clarify how to conceptualize global justice,how conceptual indicators can be selected and justified by theories,and how those indicators can be conceptually consistent with the concept of global justice.Global justice is a broad concept that is composed of multi-level and multidimensional aspects belonging to both normative and empirical realities.A coherent and integrated theoretical framework that covers the normative basis and various empirical dimensions is therefore much needed in order to address some of the basic and important questions under study.The paper seeks to synthesize the multiple theories and conceptions of global justice that exist in the academic discourse and literature into three main theoretical approaches to global justice-rights based,good based,and virtue based.These three approaches are a good sample of and reflect well the strengths of the different theoretical,intellectual and cultural traditions at play in the study of global justice.From this perspective,the synthesis of the three approaches is meant to provide us with a coherent theoretical framework that serves as the normative basis and justifies the selection of indicators for measurement.