镍催化支链1,3-二烯的氢烷基化反应机理探究

随着算法和理论化学的发展,量子化学计算已被用于解释和预测各种化学实验。镍催化共轭烯烃的氢烷基化反应是一类重要的有机化学反应,其机理一直是有机化学家关注的焦点。本文利用密度泛函理论(DFT)对Mazet课题组开发的一个氢烷基化反应进行了详细的研究,得到了该反应可能的机理模型。在此背景下,对反应的极具吸引力的区域选择性进行了探讨和合理解释。

Clinical significance of HBME-1,Galectin-3,and CK19 expression and the status of BRAF mutation in papillary thyroid carcinoma

Objective The aim of this study was to explore the clinical significance of the expression of proteins human bone marrow endothelial cell markers(HBME-1), Galectin-3, and cytokeratin19(CK19), as well as the status of v-raf murine sarcoma viral oncogene homolog B1(BRAF) mutation in papillary thyroid carcinoma(PTC). Methods Immunohistochemical staining was performed in 82 specimens each of PTC and papillary benign lesions to detect the expression of HBME-1, Galectin-3, and CK19. Polymerase chain reaction(PCR) and gene sequencing were performed on 60 specimens each of PTC and papillary benign lesions to detect the status of BRAF mutation. Results The positive expression ratios of HBME-1, Galectin-3, and CK19 in PTC were 98.8%, 97.6% and 100% respectively, which were significantly higher than the expressions in papillary benign lesions(P < 0.05). No significant relationship was observed between the expression of these makers and the clinicopathological features of PTC. The sensitivity of co-expression of HBME-1 and CK19 or HBME-1 and Galectin-3 as diagnostic criteria of PTC was 99.9%, with a specificity of 95.4%. BRAF mutation was detected in 40 of 60 PTC(66.7%) specimens. There was a statistical difference in BRAF mutations between PTC and papillary benign lesions(P < 0.05); there were no associations between BRAF mutation and the clinicopathological features of PTC. Conclusion Combined immunohistochemical staining of HBME-1, Galectin-3, and CK19 can further improve the sensitivity and specificity of differential diagnosis of PTC. BRAF mutation is a significant genetic event, which may have diagnostic value for PTC.

Adsorption of Hg(Ⅱ) from aqueous solution using thiourea functionalized chelating fiber

A fast and selective adsorbent for Hg(II) from aqueous solutions using thiourea(TU) functionalized polypropylene fiber grafted acrylic acid(PP-g-AA),PP-g-AA-TU fibers,was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The adsorption behavior of the functionalized chelating fibers for Hg(II) was investigated by static adsorption experiments,and the effects of some essential factors on adsorption of Hg(II) were examined,such as pH,initial concentration,adsorption time,coexisting cations,and temperature.The results showed that the adsorptive equilibrium could be achieved in 10 min,and the equilibrium adsorption quantity of PP-g-AA-TU fibers was 20 times that of PP-g-AA fibers.The PP-g-AA-TU fibers showed a very high adsorption rate and a good selectivity for Hg(II) over a wide range of p H.The adsorption isotherm can be well described with Langmuir model,with the maximum adsorption capacity for Hg(II) up to52.04 mg·g^(-1)and the removal of Hg(II) more than 97%.The kinetic data indicate that the adsorption process is best-fitted into the pseudo-second-order model.

Evaluation and advancement of the integrated circular economy model of farming and stock raising

The integrated circular economy model of farming and stock raising(ICEMFSR)has attracted increased attention as an effective model for solving the current irrational allocation of agricultural resources and realizing the agricultural value-added industrial chain.This study uses emergy analysis to comprehensively examine and evaluate the economic benefits,environmental pressures,and sustainable development levels of ICEMFSR in Shucheng County,China.The results show that the ICEMFSR possesses the value of popularization with optimally allocated resources in the studied region,in which the emergy yield ratio(EYR),emergy loading ratio(ELR),and emergy sustainable index(ESI)in this model accounted for 3.59,1.25,and 2.89,respectively.This result indicates a leading position in the national agricultural system.Hence,this study constructs a new model based on the coupling of emergy evaluation and multi-objective linear programming to study ICEMFSR.Consequently,the EYR,ELR,and ESI respectively varied by +24.23%,10.40%,and +38.06%after replanning of ICEMFSR.This variation implies a significant improvement in the sustainable development level of the model.In addition,the optimized scenario design for key substances is proposed based on traceability and the reduce-reuse-recycle principle,including biogasification of crop straw and enhancement of crop scientific planting capacity.

Grasping institutional complexity in infrastructure megaprojects through the multi-level governance system： A case study of the Hong Kong-Zhuhai-Macao Bridge construction

This study analyzes the design and operation of multi-level governance system for the smooth delivery of infrastructure mega-projects with high institutional complexity caused by market transition. From an institutional perspective, this study scrutinizes the structure,elements, and dynamics of the governance system of infrastructure mega-projects and then proposes an integrative framework based on the inductive case study of the Hong Kong-Zhuhai-Macao Bridge mega-project. Multiple evidences of archives, field studies, and interviews related to the case project are triangulated to further analyze the institutional effects, specifically those with government logics and market structures, on the design and operation of the three-level governance system. Results reveal that the co-evolution between governments and markets in China has shaped the vertical levels of the mega-project governance system and has further affected their evolution and operation across various stages of project development. This study contributes to the rapidly emerging research on complex system governance by proposing a systematic model of three-level mega-project governance to enhance the timely delivery of infrastructure megaprojects within budget.

Interstitial copper-doped edge contact for n-type carrier transport in black phosphorus

Black phosphorus(BP)has been shown as a promising two-dimensional(2D)material for electronic devices owing to its high carrier mobility.To realize complementary electronic circuits with 2D materials,it is important to fabricate both n-type and p-type transistors with the same channel material.By engineering the contact region with copper(Cu)-doped BP,here we demonstrate an n-type carrier transport in BP field-effect transistors(FETs),which usually exhibit strongly p-type characteristics.Cu metal atoms are found to severely penetrate into the BP flakes,which forms interstitial Cu(Cuint)-doped edge contact and facilitates the electron transport in BP.Our BP FETs in backgated configuration exhibit n-type dominant characteristics with a high electron mobility of^138 cm^2 V^−1 s^−1 at room temperature.The Schottky barrier height for electrons is relatively low because of the edge contact between Cuint-doped BP and pristine BP channel.The contact doping of BP by highly mobile Cu atoms gives rise to n-type transport property of BP FETs.Furthermore,we demonstrate a p-n junction on the same BP flake with asymmetric contact.This strategy on contact engineering can be further extended to other 2D materials.

Presenting Little q-Schur Algebras uk（2, r）

Little q-Schur algebras were introduced as homomorphic images of the infinitesimal quantum groups by Du, Fu and Wang. In this paper, we obtain a presentation by generators and relations for little q-Schur algebras uk（2, r）.

Carboxylatopillarene-Modified Reduced Graphene Oxides with High Water Dispersibility for Fluorescent Dye Sensing

Carboxylated pillar[5]arene(CP5)macrocycles were modified onto the surface of reduced graphene oxide(RGO)via covalent bonds to form new pillarene-functionalized RGO nanosheets,i.e.,RGO-CP5.The obtained RGO-CP5 nanosheets capable of molecular recognition exhibited much better water-dispersibility and enhanced fluorescence-quenching property as compared with native RGO.This new sensing platform holds great potentials in the sensing and detection of analytes,such as organic dye molecules and pesticides,in aqueous solutions.

金基底引导制备二维黑磷及其生长机理

二维材料是近年来材料科学和凝聚态物理学的前沿研究方向.在众多的二维材料中,黑磷(black phosphorus,BP)因其独特的带隙、优异的光学和电学性质、各向异性等特性而受到研究人员的广泛关注.如何可控制备二维薄层BP是该领域的难题之一.本工作系统研究了基底对BP生长的影响,结果表明金基底对BP的生长具有重要促进作用.在此基础上,使用镀有金薄膜的硅基底为生长衬底,通过设计限域生长空间和调控温度梯度,在全新的生长体系中实现了BP纳米片的直接生长,并探讨了其生长机理.本研究所报道的结果为实现二维薄层BP的制备提供了一条新思路.

用双极性p-n异质结器件进行传感器内卷积处理

Image sensing is a critical component of modern machine vision technology development.The traditional silicon-based photodiodes possess inflexible responsivity and energy band structures that are hard to manipulate by an external field,limiting the system’s ability to process picture data[1].Additionally,existing memristor arrays can do some computation in hardware but cannot directly respond to optical signals,so it is necessary to use additional image sensors to convert optical signals into electrical signals before implementing further signal processing.As a result of their separate data processing units and image sensors,conventional image sensing systems face problems such as slow operation and excessive power consumption that can result in transmitting and processing huge amounts of duplicate information[2,3].

Mechanistic insights into the rhodium-catalyzed aryl C-H carboxylation

The recently reported Rh(Ⅱ)-catalyzed direct C-H bond activation and lactonization of 2-arylphenols uncovers an attractive strategy to prepare coumarin derivatives with novel chemoselectivity.Motivated by the mechanistic ambiguity(on the origin of the chemoselectivity and the details for lactonization etc.),we conducted a detailed mechanistic study for the rhodium-catalyzed lactonization of 2-arylphenols with density functional theory(DFT)calculations.The results suggest that the reaction occurs via the coordination exchange,C-H bond activation,carboxylation,protonation and lactonization steps.The rate-determining step is the carboxylation,in which CO_(2) favorably inserts into the Rh-C bond(instead of the more nucleophilic Rh-O bond).The protonation step after carboxylation is critical,which makes the subsequent CO_(2)-assisted lactonization feasible.Interestingly,the corresponding pK_(a) value of the base can reasonably predict the reaction energy barrier of the C-H bond activation step.The calculations will provide insights and suggestions for developing and advancing the subsequent C-H bond activation carboxylation reaction.