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"Zhu, Yi"
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Enantioselective C(sp 3 )‒H bond activation by chiral transition metal catalysts
Although organic compounds consist mostly of carbon and hydrogen atoms, strategies for chemical synthesis have traditionally targeted the handful of more reactive interspersed oxygens, nitrogens, and halogens. Modifying C–H bonds directly is a more appealing approach, but selectivity remains a challenge. Saint-Denis
et al.
review recent progress in using transition metal catalysis to break just one of two mirror-image C–H bonds and then append a more complex substituent in its place. Ligand design has proven crucial to differentiate these otherwise similar bonds in a variety of molecular settings.
Science
, this issue p.
eaao4798
Organic molecules are rich in carbon-hydrogen bonds; consequently, the transformation of C–H bonds to new functionalities (such as C–C, C–N, and C–O bonds) has garnered much attention by the synthetic chemistry community. The utility of C–H activation in organic synthesis, however, cannot be fully realized until chemists achieve stereocontrol in the modification of C–H bonds. This Review highlights recent efforts to enantioselectively functionalize C(sp
3
)–H bonds via transition metal catalysis, with an emphasis on key principles for both the development of chiral ligand scaffolds that can accelerate metalation of C(sp
3
)–H bonds and stereomodels for asymmetric metalation of prochiral C–H bonds by these catalysts.
Journal Article
Lun yu = The Analects of Confucius
Ben shu cai yong ying han dui zhao de xing shi shou lu. shi zhong guo gu dai ru jia de yi bu zhong yao jing dian, Shi kong zi di zi ji qi zai chuan di zi guan yu kong zi yan xing de ji lu.
Book
Constraints on scalar–tensor theory of gravity by the recent observational results on gravitational waves
The speed of gravitational waves provides us a new tool to test alternative theories of gravity. The constraint on the speed of gravitational waves from GW170817 and GRB170817A is used to test some classes of Horndeski theory. In particular, we consider the coupling of a scalar field to Einstein tensor and the coupling of the Gauss–Bonnet term to a scalar field. The coupling strength of the Gauss–Bonnet coupling is constrained to be in the order of \\[10^{-15}\\]. In the Horndeski theory we show that in order for this theory to satisfy the stringent constraint on the speed of GWs the mass scale M introduced in the non-minimally derivative coupling is constrained to be in the range \\[10^{15} \\,\\,\\text {GeV}\\gg M \\gtrsim 2\\times 10^{-35}\\] GeV taking also under consideration the early times upper bound for the mass scale M. The large mass ranges require no fine-tuning because the effect of non-minimally derivative coupling is negligible at late times.
Journal Article
Zhu Guangqian and Benedetto Croce on aesthetic thought : with a translation of the Wenyi xinlixue (The psychology of art and literature)
\"In Zhu Guangqian and Benedetto Croce on Aesthetic Thought, Mario Sabattini analyses Croce's influence on the aesthetic thought of Zhu Guangqian. Zhu Guangqian is one of the most representative figures of contemporary Chinese aesthetics. Since the '30s, he had an active role in China both on the literary and philosophical scenes, and, through his writings, he exerted an important influence in the moulding of numerous generations of intellectuals. Some of his works have been widely read, and they still provoke considerable interest in China, on the mainland as well as in Taiwan and Hong Kong. The volume also presents a revised translation of Zhu Guangqian's Wenyi xinlixue (Psychology of Art and Literature)\"-- Provided by publisher.
Book
Constraints on primordial curvature spectrum from primordial black holes and scalar-induced gravitational waves
The observational data of primordial black holes and scalar-induced gravitational waves can constrain the primordial curvature perturbation at small scales. We parameterize the primordial curvature perturbation by a broken power law form and find that it is consistent with many inflation models that can produce primordial black holes, such as nonminimal derivative coupling inflation, scalar–tensor inflation, Gauss–Bonnet inflation, and K/G inflation. The constraints from primordial black holes on the primordial curvature power spectrum with the broken power law form are obtained, where the fraction of primordial black holes in dark matter is calculated by the peak theory. Both the real-space top-hat and the Gaussian window functions are considered. The constraints on the amplitude of primordial curvature perturbation with Gaussian window function are around three times larger than those with real-space top-hat window function. The constraints on the primordial curvature perturbation from the NANOGrav 12.5 years data sets are displayed, where the NANOGrav signals are assumed as the scalar-induced gravitational waves, and only the first five frequency bins are used.
Journal Article
Gap Junction-Dependent and -Independent Functions of Connexin43 in Biology
For the first time in animal evolution, the emergence of gap junctions allowed direct exchanges of cellular substances for communication between two cells. Innexin proteins constituted primordial gap junctions until the connexin protein emerged in deuterostomes and took over the gap junction function. After hundreds of millions of years of gene duplication, the connexin gene family now comprises 21 members in the human genome. Notably, GJA1, which encodes the Connexin43 protein, is one of the most widely expressed and commonly studied connexin genes. The loss of Gja1 in mice leads to swelling and a blockage of the right ventricular outflow tract and death of the embryos at birth, suggesting a vital role of Connexin43 gap junction in heart development. Since then, the importance of Connexin43-mediated gap junction function has been constantly expanded to other types of cells. Other than forming gap junctions, Connexin43 can also form hemichannels to release or uptake small molecules from the environment or even mediate many physiological processes in a gap junction-independent manner on plasma membranes. Surprisingly, Connexin43 also localizes to mitochondria in the cell, playing important roles in mitochondrial potassium import and respiration. At the molecular level, Connexin43 mRNA and protein are processed with very distinct mechanisms to yield carboxyl-terminal fragments with different sizes, which have their unique subcellular localization and distinct biological activities. Due to many exciting advancements in Connexin43 research, this review aims to start with a brief introduction of Connexin43 and then focuses on updating our knowledge of its gap junction-independent functions.
Journal Article
Gauss–Bonnet Inflation and the String Swampland
The swampland criteria are generically in tension with single-field slow-roll inflation because the first swampland criterion requires small tensor-to-scalar ratio while the second swampland criterion requires either large tensor-to-scalar ratio or large scalar spectral tilt. The challenge to single-field slow-roll inflation imposed by the swampland criteria can be avoided by modifying the relationship between the tensor-to-scalar ratio and the slow-roll parameter. We show that the Gauss–Bonnet inflation with the coupling function inversely proportional to the potential overcomes the challenge by adding a constant factor in the relationship between the tensor-to-scalar ratio and the slow-roll parameter. For the Gauss–Bonnet inflation, while the swampland criteria are satisfied, the slow-roll conditions are also fulfilled, so the scalar spectral tilt and the tensor-to-scalar ratio are consistent with the observations. We use the potentials for chaotic inflation and the E-model as examples to show that the models pass all the constraints. The Gauss–Bonnet coupling seems a way out of the swampland issue for single-field inflationary models.
Journal Article