The objective of this study was to investigate the associations between selenium exposure and cancer risk. We identified 69 studies and applied meta-analysis, meta-regression and dose-response analysis to obtain available evidence. The results indicated that high selenium exposure had a protective effect on cancer risk (pooled OR = 0.78; 95%CI: 0.73–0.83). The results of linear and nonlinear dose-response analysis indicated that high serum/plasma selenium and toenail selenium had the efficacy on cancer prevention. However, we did not find a protective efficacy of selenium supplement. High selenium exposure may have different effects on specific types of cancer. It decreased the risk of breast cancer, lung cancer, esophageal cancer, gastric cancer, and prostate cancer, but it was not associated with colorectal cancer, bladder cancer, and skin cancer.
L-Pipecolinic acid derived formamides have been developed as highly efficient and enantioselective Lewis basic organocatalysts for the reduction of N-aryl imines with trichlorosilane. Catalyst 4b afforded high isolated yields (up to 98%) and enantioselectivities (up to 96%) under mild conditions with an unprecedented substrate spectrum. Catalytic enantioselective reduction of imines represents one of the most important methods for preparing chiral amines, 1 a ubiquitous structural motif of natural products, drugs, and agrochemicals. Since the 1970s, considerable effort has been devoted to the development of this transformation, and remarkable progress has been made. 1,3 However, compared with the reduction of alkenes and ketones, relatively limited numbers of highly enantioselective procedures are currently available for the reduction of imines, and the development of efficient catalysts with high enantioselectivity has proven to be much more difficult. In particular, the highly enantio-selective catalyst with a satisfactorily broad substrate scope remains elusive. Factors contributing to the difficulty of this transformation include the difference in reactivity among imines containing different nitrogen substituents, the existence of acyclic imines as inseparable mixtures of E/Z
Gallium-based liquid metals (LMs),
with the combination of liquid
fluidity and metallic conductivity, are considered ideal conductive
components for flexible electronics. However, huge surface tension
and poor wettability seriously hinder the patterning of LMs and their
wider applications. Herein, a recyclable liquid-metal-microgel (LMM)
ink composed of LM droplets encapsulated into alginate microgel shells
is proposed. During the mechanical stirring process, the released
Ga3+ can cross-link with sodium alginate to form microgels
covering the surface of LM droplets, which exhibits shear-thinning
performance due to the formation and rupture of hydrogen bonds under
different stress conditions, making the LMM ink possess excellent
printability and superior adhesion to various substrates. Although
patterns printed with the LMM ink are not initially conductive, they
can be activated to recover conductivity by microstrain (<5%),
pressing, and freezing. Additionally, the activated LMM circuit exhibits
superior Joule heating behaviors and electrical performance in further
investigation, including excellent conductivity, significant resistance
response to strain with small hysteresis, great durability to nonplanar
forces, and so forth. Furthermore, smart electronic clothes were fabricated
and investigated by directly printing functional circuits on commercial
clothes with the LMM ink, which integrate multiple functions, including
tactile sensing, motion monitoring, human–computer interaction,
and thermal management.
Motivated by the recent numerical studies on the Chalker-Coddington network model that found a larger-thanexpected critical exponent of the localization length characterizing the integer quantum Hall plateau transitions, we revisited the exponent calculation in the continuum model and in the lattice model, both projected to the lowest Landau level or subband. Combining scaling results with or without the corrections of an irrelevant length scale, we obtain ν = 2.48 ± 0.02, which is larger but still consistent with the earlier results in the two models, unlike what was found recently in the network model. The scaling of the total number of conducting states, as determined by the Chern number calculation, is accompanied by an effective irrelevant length scale exponent y = 4.3 in the lattice model, indicating that the irrelevant perturbations are insignificant in the topology number calculation.
Liquid-metal (LM)-based flexible and stretchable electronics have attracted widespread interest in wearable health monitoring, electronic skins, and soft robotics. However, it is challenging to directly pattern LMs on soft substrates...
Hydrogel-based flexible electronics have caused widespread interest in recent years. However, current hydrogel electronics have its limitations, such as poor biocompatibility, non-reusability, low electrical response to deformation and functionally single....
L-Piperazine-2-carboxylic acid derived N-formamides have been developed as highly enantioselective Lewis basic catalysts for the hydrosilylation of N-aryl imines with trichlorosilane. The arene sulfonyl group on N4 was found to be critical for the high enantioselectivity of the catalyst. High isolated yields (up to 99%) and enantioselectivities (up to 97%) were obtained for a broad range of substrates, including aromatic and aliphatic ketimines, particularly those with R 2 as relatively bulky alkyl groups. Asymmetric Lewis base catalysis has proven to be a powerful and viable asymmetric synthetic method, of which the most successful applications have been in allylations and aldol reactions using trichlorosilylated reagents. 1 Recently, asym-metric reduction of imines, a useful but challenging reaction for the production of chiral amines, 2,3 was also effected by Lewis base catalysis. 4 Matsumura first disclosed that L-proline derived Lewis basic N-formamide 1 (Figure 1) catalyzed the reduction of N-aryl ketimines with trichloro-silane (HSiCl 3) in modest enantioselectivity (up to 66% ee). 4a Later, Malkov and Kocovsky reported that L-valine derived catalyst 2 significantly improved the enantioselectivity (up to 92% ee). 4b,c,5 In our recent publication, we presented a L-pipecolinic acid derived Lewis basic catalyst (3) that afforded the highest level of enantioselectivities (up to 96% ee) with an exceptional substrate spectrum. 6 Encouraged by these results, we continued to search for new highly efficient
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