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901.
Nguyen Ngoc Dong Quan 《Monatshefte für Mathematik》2012,168(2):191-214
We give a sufficient condition using the Brauer?CManin obstruction under which certain quartic curves have no rational points. Using this sufficient condition, we construct two families of genus one quartic curves violating the Hasse principle explained by the Brauer?CManin obstruction. 相似文献
902.
The multi-attribute grey target decision method for attribute value within three-parameter interval grey number 总被引:1,自引:0,他引:1
Based on the grey system theory and methods, the grey-target decision-making problem is discussed, in which the attribute values are grey numbers and the maximum probability of the value of grey number is known. Firstly, the optimal effect vector is the positive bull’s-eye and positive bull’s-eye distance of each scheme is defined. Subjectively or objectively weighting method is integrated to determine the index weight and integrated optimization model of index weight is established. Finally, the critical effect vector is the negative bull’s-eye and negative bull’s-eye distance of each scheme is defined, then relative bull’s-eye distance and comprehensive the bull’s-eye distance of grey target decision-making are given. An example is also presented to illustrate the usefulness and effectiveness of the methods obtained in this paper and provides a new idea for grey target decision-making method research. 相似文献
903.
We give a new proof of the structure theorem for PSH—algebras, and of a formula for primitives 相似文献
904.
The work strengthens the result established by L. Cohen on uncertainty principle involving phase derivative. We propose stronger uncertainty principles not only in the classical setting for Fourier transform, but also for self-adjoint operators. We also deduce the conditions that give rise to the equal relation of the uncertainty principle. Examples are provided to show that the new uncertainty principle is truly sharper than the existing ones in literature. 相似文献
905.
We introduce two new methods for solving a backward heat conduction problem. For these two methods, we give a stability analysis with new error estimates. Meanwhile, we investigate the roles of the regularization parameters in these two methods. Numerical results show that our algorithm is effective. 相似文献
906.
Ling Huang Wanting Su Lin Zhu Jiangfeng Li Wei Quan Juyoung Yoon Weiying Lin 《Angewandte Chemie (International ed. in English)》2023,62(9):e202217508
Neutrophil elastase (NE) plays a key role in chronic inflammation and acute responses to infection and injury. Effective disease interventions thus call for precise identification of NE to aid the clinical treatment of such diseases. However, the detection process suffers from the interference of structural changes of NE. Herein, we introduce a molecular probe with high biocompatibility to overcome the interference, which was achieved by combining theoretical calculations and experimental studies, that permits highly specific and sensitive detection of NE in cells and in vivo. The upregulated NE accumulation was specifically measured in inflammation by ratiometric photoacoustic and near-infrared fluorescence imaging, providing a new method for developing more specific fluorogenic probes for other enzymes. 相似文献
907.
Lin Chen Quan Qu Chuan-Kun Ran Wei Wang Dr. Wei Zhang Yi He Dr. Li-Li Liao Prof. Dr. Jian-Heng Ye Prof. Dr. Da-Gang Yu 《Angewandte Chemie (International ed. in English)》2023,62(11):e202217918
Visible-light photocatalytic carboxylation with CO2 is highly important. However, it still remains challenging for reluctant substrates with low reduction potentials. Herein, we report a novel photocatalytic carboxylation of C−N bonds in cyclic amines with CO2 via consecutive photo-induced electron transfer (ConPET). It is also the first photocatalytic reductive ring-opening reaction of azetidines, pyrrolidines and piperidines. This strategy is practical to transform a variety of easily available cyclic amines to valuable β-, γ-, δ- and ϵ-amino acids in moderate-to-excellent yields. Moreover, the method also features mild and transition-metal-free conditions, high selectivity, good functional-group tolerance, facile scalability and product derivations. Mechanistic studies indicate that the ConPET might be the key to generating highly reactive photocatalysts, which enable the reductive activation of cyclic amines to generate carbon radicals and carbanions as the key intermediates. 相似文献
908.
Jun-Hao Zhang Hui Xu Dr. Xiaodong Tang Prof. Dr. Yanfeng Dang Prof. Dr. Fa-Guang Zhang Prof. Dr. Jun-An Ma 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305315
Catalytic asymmetric hydrogenation of enamido phosphorus derivatives is one of the most efficient methods for the construction of chiral amino phosphorus products, among which the congested tetra-substituted substrates remains an unaddressed challenge. In this study, we utilize a commercially available Rh-Josiphos system for the efficient and stereoselective hydrogenation of a wide set of tetra-substituted cyclic β-enamido phosphonates/phosphine oxides, thus enabling access to chiral β-amino phosphorus compounds featuring two vicinal stereocenters. This protocol was broadly applicable to different ring systems possessing various phosphonate/phosphine oxide groups and further applied in the preparation of amino-phosphine ligands. DFT mechanistic explorations indicate that the C=C migratory insertion into RhIII−H bond could be the rate- and stereo-determining step. The origins of stereoselectivity are revealed through distortion/interaction analysis, which is primarily regulated by distinguished dispersion interactions and steric repulsions. 相似文献
909.
Dr. Soumya Jyoti Singha Roy Conor Loynd Delilah Jewel Sarah E. Canarelli Elise D. Ficaretta Quan A. Pham Prof. Dr. Eranthie Weerapana Prof. Dr. Abhishek Chatterjee 《Angewandte Chemie (International ed. in English)》2023,62(27):e202300961
We have developed a novel visible-light-catalyzed bioconjugation reaction, PhotoCLIC, that enables chemoselective attachment of diverse aromatic amine reagents onto a site-specifically installed 5-hydroxytryptophan residue (5HTP) on full-length proteins of varied complexity. The reaction uses catalytic amounts of methylene blue and blue/red light-emitting diodes (455/650 nm) for rapid site-specific protein bioconjugation. Characterization of the PhotoCLIC product reveals a unique structure formed likely through a singlet oxygen-dependent modification of 5HTP. PhotoCLIC has a wide substrate scope and its compatibility with strain-promoted azide-alkyne click reaction, enables site-specific dual-labeling of a target protein. 相似文献
910.
Xuan Cheng Quan Yin Yu-Xuan Jiang Ling-Feng Jiang Si-Yuan Li Yi-Fei Cheng Xin-Chang Sun Lujun Peng Prof. Cheng Zhong Prof. Qing-Hai Deng 《Angewandte Chemie (International ed. in English)》2023,62(18):e202302521
Organic nitrates are broadly applied as pharmaceuticals (acting as efficient nitric oxide donor), energetic materials, building blocks in organic synthesis, etc. However, practical and direct methods to access organic nitrates efficiently are still rare, mainly due to the lack of powerful nitrooxylating reagents. Herein, we report bench-stable and highly reactive noncyclic hypervalent iodine nitrooxylating reagents, oxybis(aryl-λ3-iodanediyl) dinitrates (OAIDNs, 2 ), which are prepared just by using aryliodine diacetate and HNO3. The reagents are used to achieve a mild and operationally simple protocol to access diverse organic nitrates. By employing of 2 , zinc-catalyzed regioselective nitrooxylation of cyclopropyl silyl ethers is realized efficiently to access the corresponding β-nitrooxy ketones with high functional-group tolerance. Moreover, a series of direct and catalyst-free nitrooxylations of enolizable C−H bonds are carried out smoothly to afford the desired organic nitrates within minutes by just mixing the substrates with 2 in dichloromethane. 相似文献