5,047 research outputs found
Recent advances in organic electrochemical functionalizations for specialty chemicals
No full texthttp://dx.doi.org/10.13039/501100001659 Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/501100000781 European Research Counci
On the Rational Polytopes with Chvatal Rank 1
No full textWe study the following problem: given a rational polytope with Chvatal rank 1, does it contain an integer point? Boyd and Pulleyblank observed that this problem is in the complexity class NP boolean AND\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}\end{document} co-NP, an indication that it is probably not NP-complete. It is open whether there is a polynomial time algorithm to solve the problem, and we give several special classes where this is indeed the case. We show that any compact convex set whose Chvatal closure is empty has an integer width of at most n, and we give an example showing that this bound is tight within an additive constant of 1. This determines the time complexity of a Lenstra-type algorithm. However, the promise that a polytope has Chvatal rank 1 seems hard to verify. We prove that deciding emptiness of the Chvatal closure of a rational polytope given by its linear description is NP-complete, even when the polytope is contained in the unit hypercube or is a rational simplex and it does not contain any integer point.
The Influence of Stock Liquidity on Tail Risk of Stock Market: An Empirical Research Based on POT Model
No full textIn view of the irrationality of the normal hypothesis of the value-at-risk model， the POT model based on the generalized pareto distribution is used to measure the tail risk of China's stock market， and the influence of stock liquidity on the tail risk of China's stock market is explored by grouping the sample data according to liquidity. In the research, the slope change point theory in statistical theory is introduced into the traditional threshold selection method， which effectively avoids the subjectivity problem when determining the optimal threshold. The test results show that for the measurement of tail risk of the stock market, the VaR value at the 95% confidence level is more reliable than the estimated result of the VaR value at the 90% confidence level, and the estimated value shows that tail risk and liquidity change in the opposite direction, that is， the smaller the stock liquidity is, the greater the market tail risk
FIGURE 1 in The Epimedium wushanense (Berberidaceae) species complex, with one new species from Sichuan, China
No full textFIGURE 1. Distribution map of E. wushanense, E. jinchengshanense, E. ilicifolium, and E. pseudowushanense.Published as part of Zhang, Yanjun, Dang, Haishan, Li, Jianqiang & Wang, Ying, 2014, The Epimedium wushanense (Berberidaceae) species complex, with one new species from Sichuan, China, pp. 39-45 in Phytotaxa 172 (1) on page 41, DOI: 10.11646/phytotaxa.172.1.5, http://zenodo.org/record/514223
Abundant Lithiophilic VO2/V8C7 Heterostructures Boost Charge Transfer toward High-Rate Lithium Storage
No full textThe construction of a heterogeneous structure on an electrode can enhance its absorption energy, thereby improving ionic diffusion and reaction kinetics. Herein, hyperdispersed VO2/V8C7 nano-heterostructures anchored on carbon nanofibers (VO2/V8C7@CNF), which are further utilized as a lithium anode are successfully developed. The self-supported VO2/V8C7@CNF electrode features a synergistic effect, resulting from its well-dispersed nano-heterostructure, induced hetero-interfacial electric field, and conspicuous lithiophilicity. This anode thus facilitates rapid Li+ ions diffusion and charge transfer, resulting in high-rate performance and uniform Li deposition. It exhibits a reversible specific capacity of as high as 674.8 mA h g(-1) at a current density of 0.1 A g(-1) and maintains a high-rate capability of 205.3 mA h g(-1) at a current density of as high as 5.0 A g(-1) even after undergoing 1000 charge/discharge cycles. The Li-ion nucleation overpotential on this anode is significantly reduced to 27 mV. The hyperdispersed nano-heterostructure strategy offers a universal blueprint for the fabrication of high-performance anodes not only for lithium and other batteries.Natural Science Foundation of Hubei Province; National Natural Scienc
FIGURE 4. E. ilicifolium. A. Flower. B in The Epimedium wushanense (Berberidaceae) species complex, with one new species from Sichuan, China
No full textFIGURE 4. E. ilicifolium. A. Flower. B. Outer sepal (outer pair). C. Outer sepal (inner pair). D. Inner sepal. E. Petal (from Y. J. Zhang 109, HIB).Published as part of Zhang, Yanjun, Dang, Haishan, Li, Jianqiang & Wang, Ying, 2014, The Epimedium wushanense (Berberidaceae) species complex, with one new species from Sichuan, China, pp. 39-45 in Phytotaxa 172 (1) on page 44, DOI: 10.11646/phytotaxa.172.1.5, http://zenodo.org/record/514223
FIGURE 3. E. jinchengshanense. A. Flowering stem with stem leaves. B. Rhizome. C. Flower. D. Petal. E. Inner sepal. F. Stamen. G in The Epimedium wushanense (Berberidaceae) species complex, with one new species from Sichuan, China
No full textFIGURE 3. E. jinchengshanense. A. Flowering stem with stem leaves. B. Rhizome. C. Flower. D. Petal. E. Inner sepal. F. Stamen. G. Gynoecium. (from Sichuan Econ. Pl. Exped. Nan 2, CDBI, KUN, SM).Published as part of Zhang, Yanjun, Dang, Haishan, Li, Jianqiang & Wang, Ying, 2014, The Epimedium wushanense (Berberidaceae) species complex, with one new species from Sichuan, China, pp. 39-45 in Phytotaxa 172 (1) on page 43, DOI: 10.11646/phytotaxa.172.1.5, http://zenodo.org/record/514223
sj-pdf-1-prk-10.1177_14686783211045834 – Supplemental Material for A new Bi(III)-based coordination complex: Treatment and nursing application values on pediatric pneumonia
No full textSupplemental Material, sj-pdf-1-prk-10.1177_14686783211045834 for A new Bi(III)-based coordination complex: Treatment and nursing application values on pediatric pneumonia by Jianli Lu, Hong Han, Bo Li and Yanjun Han in Progress in Reaction Kinetics and Mechanism</p
Recent Progress in Electrochemical Late-Stage C(sp2)–H Functionalization
No full textAbstract Late-stage C–H functionalization has gained rapid development as a key approach in modern synthetic methodology, particularly for the transformation of structurally complex molecules. This strategy has reformed retrosynthetic logic and improved synthetic efficiency. C(sp2)–H functionalization, as a pivotal part in late-stage functionalization, has significantly promoted the development of medicinal chemistry. However, the latter often employ transition metal catalysts, in combination with stoichiometric amounts of chemical oxidants, which severely compromise their sustainability, functional group tolerance, and their extension to industrial applications. In sharp contrast, electrochemical late-stage C(sp2)–H functionalization has emerged as a more sustainable and environmentally friendly alternative, where electrons are used as clean redox agents. Therefore, this approach obviates the need for toxic chemical oxidants, enabling reactions to be operative under milder conditions, allowing for a wide scope of redox transformations. In this review, we highlight the recent progress in the electrochemical late-stage functionalization of C(sp2)–H bonds from 2019 to 2025, with particular focus on the formation of C(sp2)–C, C(sp2)–O, C(sp2)–N, and C(sp2)–P bonds
Thioether-enabled palladium-catalyzed atroposelective C–H olefination for N–C and C–C axial chirality
No full textThioethers allowed for highly atroposelective C–H olefinations by a palladium/chiral phosphoric acid catalytic system under ambient air
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