The printable polyamide 12 (PA12) nanocomposite filaments with 6 wt % graphene nanoplatelets (GNPs) for fused deposition modeling (FDM) were prepared by melting compounding and smoothly printed via a commercial FDM three-dimensional (3D) printer. The thermal conductivity (k) and elastic modulus (E) of 3D printed PA12/GNPs parts along to the printing direction had an increase by 51.4% and 7% than that of compression molded parts, which is due to the GNPs preferentially aligning along to the printing direction. Along with these improved properties, ultimate tensile strength of 3D printed PA12/GNPs parts was well maintained. These results indicate that FDM is a new way to achieve PA12/GNPs parts with enhanced k over compression moulding, which could contribute to realize efficient and flexible heat management for a wide range of applications.
Transition metal-catalyzed carbene insertion into X-H bonds (X = N, O, S, and C) represents a typical carbene transfer reaction and has been widely used in organic synthesis. The enantioselectivity-determining step in some of these insertion reactions is the proton transfer of active intermediates such as ylides, metal enolates, or free enols. Since most of the traditional chiral transition metal catalysts tend to dissociate from these active intermediates and cannot be involved in the proton-transfer step, enantiocontrol of these insertion reactions has long been a challenging task. Since 2011, we have developed chiral spiro phosphoric acids as chiral proton-transfer shuttle (CPTS) catalysts, which have been proven to be efficient catalysts for the proton transfer of active intermediates in carbene insertion reactions. Upon combining with achiral dirhodium catalysts, the CPTS catalysts accomplish highly enantioselective insertions of N-H, S-H, and C-H bonds. Herein, a number of important chiral building blocks, including α-amino acid derivatives, α-amino ketones, α-thioesters, and α,α-diaryl acetates, were prepared with high yields and high enantioselectivities through these insertion reactions.
Thef irst highly enantioselective intramolecular N À Hb ondi nsertion was realized by using copper catalysts modified with chiral spirobisoxazoline ligands,w hich provides an ovels trategyf or the synthesis of chiral 2-carboxytetrahydroquinolines. This reactionf eatures fast reactionr ate,h igh yield, high enantioselectivity,a nd mild reactionc onditions.
development of multifunctional hydrogels is gaining a lot of attention owing
to its application in electronic skins, wearable electronics, and
soft robotics. In this study, an effective and facile one-step preparation
strategy is developed to fabricate a multifunctional nanocomposite
hydrogel consisting of sodium alginate/sodium polyacrylate/layered
rare-earth hydroxide (LRH), where LRH plays multiple roles as a co-cross-linker and ionic carrier and
is also the origin of fluorescence. The obtained LRH-based composite
hydrogel exhibits excellent three-dimensional printing performance
at room temperature. When exposed to different humidity conditions,
the hydrogel exhibits humidity-dependent electromechanical properties.
The multiple functions of the resultant hydrogel are easily realized
by just relying on the addition of cationic LRH nanoplates. A skinlike
motion sensor with transparency is fabricated based on the printed
hydrogel and is used to monitor human motion. Owing to the fluorescence
characteristics of lanthanide ions (Eu3+ and Tb3+) from LRH, the hydrogel shows highly tunable multicolored photoluminescence
by adjusting the LRH constituent. This study reveals that the multifunctional
hydrogels have potential for applications in sensing.
Many studies have evaluated the association between serum levels of mannose-binding lectin (MBL) and sepsis; however, the findings are inconclusive and conflicting. For a better understanding of MBL in sepsis, we conducted a comprehensive meta-analysis. Potential relevant studies were identified covering Science Citation Index, the Cochrane Library, PubMed, Embase, CINAHL, and Current Contents Index databases. Two reviewers extracted data and assessed studies independently. Statistical analyses were conducted with the version 12.0 STATA statistical software. Ten papers were collected for meta-analysis. Results identified that sepsis patients had considerably lower MBL level than those in the controls (standardized mean difference (SMD) = 1.59, 95 % confidence interval (95%CI) = 0.86∼2.31, P < 0.001). Ethnicity-subgroup analysis showed that sepsis patients were associated with decreased serum MBL level in contrast to the healthy controls in Asians (SMD = 3.07, 95%CI = 1.27∼4.88, P = 0.001) and Caucasians (SMD = 1.00, 95%CI = 0.35∼1.65, P = 0.003). In the group-stratified subgroup analysis, subjects with lower serum MBL level did underpin susceptibility to sepsis in the infants subgroup (SMD = 2.57, 95%CI = 1.59∼3.55, P < 0.001); however, this was not the case in the adults subgroup (SMD = 0.13, 95%CI = -1.30∼1.55, P = 0.862). Our study suggests an important involvement of serum MBL level in sepsis patients considering their lower level compared to controls, especially among infants.
An enantioselective direct Mannich reaction of different acetophenone derivatives with various substituted seven‐membered cyclic imines using (S)‐azetidine‐2‐carboxylic acid as an organocatalyst is described, which provides an efficient access to optically active 11‐substituted‐10,11‐dihydrodibenzo[b,f][1,4]oxazepine derivatives with 87–95 % ee. For α,β‐unsaturated ketone benzalacetone, the desired Mannich product was obtained with 72 % ee. A plausible transition state is established to explain the observed absolute stereochemistry of the Mannich products. The reaction can also be performed on a gram scale with no adverse effects on the yield and enantioselectivity. Furthermore, some simple transformations involving the Wittig olefination and the decarboxylative reduction of the Mannich products were performed.
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