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991.
We present a dark matter model to explain the excess events in the electron recoil data recently reported by the Xenon1 T experiment. In our model, dark matter χ annihilates into a pair of on-shell particles Φ, which subsequently decay into the ψψ final state;ψ interacts with electrons to generate the observed excess events. Because of the mass hierarchy, the velocity of ψ can be rather large and can have an extended distribution, providing a good fit to the electron recoil energy spectrum. We estimate the flux of ψ from dark matter annihilations in the galaxy and further determine the interaction cross section, which is sizable but sufficiently small to allow ψ to penetrate the rocks to reach the underground labs. 相似文献
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994.
Van T. Tran Zi-Qi Li Timothy J. Gallagher Joseph Derosa Prof. Peng Liu Prof. Keary M. Engle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7095-7100
Allylation and conjunctive cross-coupling represent two useful, yet largely distinct, reactivity paradigms in catalysis. The union of these two processes would offer exciting possibilities in organic synthesis but remains largely unknown. Herein, we report the use of allyl electrophiles in nickel-catalyzed conjunctive cross-coupling with a non-conjugated alkene and dimethylzinc. The transformation is enabled by weakly coordinating, monodentate aza-heterocycle directing groups that are useful building blocks in synthesis, including saccharin, pyridones, pyrazoles, and triazoles. The reaction occurs under mild conditions and is compatible with a wide range of allyl electrophiles. High chemoselectivity through substrate directivity is demonstrated by the facile reactivity of the β-γ alkene of the starting material, whereas the ϵ-ζ alkene of the product is preserved. The generality of this approach is further illustrated through the development of an analogous method with alkyne substrates. Mechanistic studies reveal the importance of the dissociation of the weakly coordinating directing group to allow the allyl moiety to bind and facilitate C(sp3)−C(sp3) reductive elimination. 相似文献
995.
Vi Tran Bernd Walkenfort Matthias Knig Mohammad Salehi Sebastian Schlücker 《Angewandte Chemie (International ed. in English)》2019,58(2):442-446
The design of a portable Raman/SERS‐LFA reader with line illumination using a custom‐made fiber optic probe for rapid, quantitative, and ultrasensitive point‐of‐care testing (POCT) is presented. The pregnancy hormone human chorionic gonadotropin (hCG) is detectable in clinical samples within only 2–5 s down to approximately 1.6 mIU mL?1. This acquisition time is several orders of magnitude shorter than those of existing approaches requiring expensive Raman instrumentation, and the method is 15‐times more sensitive than a commercially available lateral flow assay (LFA) as the gold standard. The SERS‐LFA technology paves the way for affordable, quantitative, and ultrasensitive POCT with multiplexing potential in real‐world applications, ranging from clinical chemistry to food and environmental analysis as well as drug and biowarfare agent testing. 相似文献
996.
Lucas J. Oxtoby Zi-Qi Li Van T. Tran Tuğçe G. Erbay Ruohan Deng Prof. Peng Liu Prof. Keary M. Engle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8970-8975
Metal-coordinating directing groups have seen extensive use in the field of transition-metal-catalyzed alkene functionalization; however, their waste-generating installation and removal steps limit the efficiency and practicality of reactions that rely on their use. Inspired by developments in asymmetric organocatalysis, where reactions rely on reversible covalent interactions between an organic substrate and a chiral mediator, we have developed a transient-directing-group approach to reductive Heck hydroarylation of alkenyl benzaldehyde substrates that proceeds under mild conditions. Highly stereoselective migratory insertion is facilitated by in situ formation of an imine from catalytic amounts of a commercially available amino acid additive. Computational studies reveal an unusual mode of enantioinduction by the remote chiral center in the transient directing group. 相似文献
997.
Russian Journal of Organic Chemistry - 1-Methyl-3-sulfo-1H-imidazol-3-ium chloride ([Msim]Cl) catalyzed the condensation of β-naphthol with aromatic aldehydes under microwave irradiation. This... 相似文献
998.
Nguyen Van-Trong Tran Long-Ho Van Thanh-Khue Le Dinh-Vu 《Journal of Analytical Chemistry》2022,77(5):604-610
Journal of Analytical Chemistry - Triple quadrupole mass spectrometry was used for the direct, quick and quantitative determination of chlorpyrifos residue in bell peppers using the QuEChERS... 相似文献
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Oanh Nguyen Thi Tu Ha Pham Tran Thu Giap Tran Huu Oanh Vu Thi Kim Hang Nguyen Thi Minh Van The Nguyen Thuc Dinh Ngoc Fedeli Donatella Gabbianelli Rosita Huong Phung Thanh Van Hung Nguyen Thanh Le Nguyen 《Chemistry of Natural Compounds》2021,57(2):355-359
Chemistry of Natural Compounds - 相似文献