A series of novel m-arene-bridged salicylaldimine-based binuclear neutral nickel(II) complexes (2,4,6-(R2)3C6H-1,3-NCH-4-X-6-R1C6H2ONi(Ph)(PPh3)2 (3a−i: R1, R2, X = Me, Me, H (3a), tBu, Me, H (3b), ...Me, Et, H (3c), tBu, Et, H (3d), H, iPr, H (3e), Me, iPr, H (3f), tBu, iPr, H (3g), Ph, iPr, H (3h), NO2, iPr, NO2 (3i), H, iPr, NO2 (3j)) are synthesized. The structure of complex 3h is further confirmed by an X-ray diffraction study showing that the two Ni centers adopt an unsymmetrical, distorted square planar geometry. In the presence or absence of the phosphine scavenger Ni(COD)2, complexes 3a−j show high catalytic activities for ethylene polymerization. The effect of substituents on ethylene polymerization is significant. The introduction of an electron-withdrawing group to the ligand framework improves the catalytic activity significantly. The influence of polymerization temperature, polymerization time, and catalyst concentration on the activities of ethylene polymerization is also investigated. Highly branched polyethylenes (46−127 branches per 1000 carbon atoms) with moderate molecular weights (M η = (1.0−169) × 104) and narrow molecular weight distributions (M w/M n = 2.3−2.4) are obtained by using complexes 3a−j as catalysts with or without a phosphine scavenger. In the presence of a polar solvent such as THF or Et2O, complex 3h polymerizes ethylene as a single-component catalyst. In comparison to the corresponding mononuclear Ni catalysts, the binuclear Ni catalysts generally show higher thermal stability, and complexes 3a, 3c, 3e, and 3f, which feature small R1 substituents, are capable of acting as single-component ethylene polymerization catalysts.
A cyclopentadienyl benzoyl ruthenium(ІІ) complex
3 was first prepared as an efficient catalyst in
Candida Antarctica lipase
B (CALB) mediated dynamic kinetic resolution (DKR) of secondary alcohols. ...With the aid of this ruthenium complex
3, (
S)-1-phenylethanol was completely racemized within 25
min, and in combination with CALB, series of secondary alcohols bearing various functional groups were resolved in an efficient DKR manner. A detailed mechanism involving the C–H bond activation was presented for the formation of complex
3 by capturing the crucial intermediate in this pathway. Related mechanistic studies were carried out to illustrate this type of DKR catalyst is based on the racemization of secondary alcohols. The novelty of its structure, its unique catalytic behavior as well as its wide scope of application of various substrates and its higher efficiency make complex
3 as an important alternative to those complexes, which are commonly used in DKR process.
A detailed mechanism involving the C–H bond activation was presented for the synthesis of complex
3 by capturing the crucial intermediate in this pathway. Related mechanistic studies were also carried out to illustrate this type of dynamic kinetic resolution (DKR) catalyst in racemizing secondary alcohols. More substrates also have been tested in this DKR system.
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Coordination self‐assemblies have attracted more and more attentions from chemists because of their beautiful structures and wide applications, and a number of excellent reviews that focus on either ...synthesis or application have been published. This paper will hightlight how to controllablly construct supramolecular assemblies based on flexibility of ligands driven by different external stimuli. Herein, not only various discrete metal‐organic aggregates including M2L2 type metallocycles, M2L4/M2L6/M3L2/M6L4/M6L8 type metallocages have been prepared, but also many well‐organized ensembles based on such new‐formed discrete aggretates have been further assembled driven by suitable external stimuli. Also, controllable self‐assembly processes accompanied with structure changes have been developed. It is expected that this paper will provide a potential strategy for developing novel coordination assemblies that can be comparable to biomacromolecules from organism.
Deficiency in regulatory T cells (Tregs) is an important mechanism underlying the pathogenesis of pediatric aplastic anemia, but its specific mechanism is unclear. In our study, we aimed to ...investigate whether IL-2/STAT5 can regulate the proliferation of Tregs in aplastic anemia (AA) by regulating their expression of B lymphocyte-induced mature protein-1 (BLIMP-1) or interferon regulatory factor 4 (IRF4). Through clinical research and animal experiments, we found that poor activation of the IL-2/STAT5 signaling pathway may leads to low expression of BLIMP-1 in Tregs of children with AA, which leads to defects in the differentiation and proliferation of Tregs in AA. In AA model mice, treatment with IL-2c reversed the decrease in Treg proportions and reduction in Blimp-1 expression in Tregs by increasing the phosphorylation of Stat5 in Tregs. In AA, deficiency of IRF4 expression in Tregs is closely related to the deficiency of Tregs, but is not regulated by the IL-2/STAT5 pathway.
A novel conformation driven self-assembly system, where four metallocycles with different conformations have been in situ self-assembled, has been reported. Interestingly, only square metallocycles ...can further interlock into polycatenanes. However, rectangular and rhombus metallocycles fail to overcome such an entropically unfavourable process, which constitutes an obstacle to the formation of polycatenanes.
TTMV::RARA is a recently reported fusion gene associated with acute promyelocytic leukemia (APL), caused by the integration of torque teno mini virus (TTMV) genomic fragments into the second intron ...of the RARA gene. Currently, there have been only six documented cases, with clinical presentations showing significant variability. Although initial responses to all-trans retinoic acid (ATRA) treatment may be observed in patients with TTMV::RARA-APL, the overall prognosis remains unfavorable among infrequent reported cases. This article presents a pediatric case that manifested as PML::RARA-negative APL with central nervous system involvement at onset. The patient experienced both intramedullary and extramedullary relapse one year after undergoing allogeneic hematopoietic stem cell transplantation. Upon identification as TTMV::RARA-APL and subsequent administration of two rounds of ATRA-based treatment, the patient rapidly developed multiple RARA ligand-binding domain mutations and demonstrated extensive resistance to ATRA and various other therapeutic interventions. Additionally, the patient experienced ARID1A mutant clone expansion and progressed MYC-targeted gene activation. This case represents the first documentation of extramedullary involvement at both the initial diagnosis and relapse stages, emphasizing the intricate clinical features and challenges associated with the rapid accumulation of multiple ATRA-resistant mutations in TTMV::RARA-APL, characterizing it as a distinct and complex sub-entity of atypical APL.
•TTMV causes atypical APL through genome fragment insertion and fusion with RARA.•TTMV::RARA-APL may predispose to central nervous system invasion.•ATRA and venetoclax regimens may provide short-term benefits for TTMV::RARA-APL.•TTMV::RARA-APL may rapidly accumulate therapy-resistant clones.
Despite the high prevalence of myopia among school-age children in China, many myopic students are reluctant to wear eyeglasses. This study estimates the effects of wearing eyeglasses on myopic ...students' academic performance, using data from a large-scale survey of middle-school students, the China Education Panel Survey. Our fuzzy regression discontinuity (RD) design, which exploits the jump in the probability of wearing eyeglasses at the threshold for myopia diagnosis, reveals that wearing eyeglasses improves myopic students' Chinese and maths test scores by 0.27 and 0.24 standard deviations, respectively.
This paper presents a unified framework for inference on parameters of the form ϕ(θ0), where θ0 is unknown but can be estimated by θˆn, and ϕ is known with null first order derivative at θ0. We show ...the “standard” bootstrap is consistent if and only if the second order derivative ϕθ0′′=0 under regularity conditions, thereby identifying a source of bootstrap failures distinct from that in Fang and Santos (2018). Two consistent bootstrap schemes are proposed: one based on Babu (1984) that applies to differentiable maps and the other one based on Fang and Santos (2018) that applies to (second order) nondifferentiable maps. As an illustration, we develop a test of existence of (potentially multiple) common conditional heteroskedasticity features that improves upon Dovonon and Renault (2013).
•We estimate the causal impact of family size on parents’ monetary investment on child education.•Identification exploits the temporary relaxation in the one-child policy in 1984–1990 in rural ...China.•We use the sex of the first-born as an instrument variable for family size.•Instrumental-variable regressions indicate little quantity-quality trade-off of children faced by the parents in rural Northwestern China.•OLS regressions tend to overestimate the quantity-quality trade-off faced by the parents.
This paper examines the quantity-quality (QQ) trade-off of children in rural Northwestern China, using data collected from Gansu Province on a set of households whose children were born between the mid-1980s and early 1990s, the period when China’s one-child policy was temporarily relaxed. Under the relaxed policy, a second child was allowed if the first-born was a girl. Exploiting this policy change, this paper uses information on the sex of the first-born in a family to capture the causal effect of family size. In contrast to the results from ordinary least-squares regressions which suggest a strong QQ trade-off, the causal estimates based on the instrumental variable method indicate that rural parents hardly face such trade-off, at least in terms of their monetary investments in child education. The instrumental-variable estimation results remain similar when information on twin births is used for identification purpose.
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