Double‐Shelled Nanocages with Cobalt Hydroxide Inner Shell and Layered Double Hydroxides Outer Shell as High‐Efficiency Polysulfide Mediator for Lithium–Sulfur Batteries

Lithium–sulfur (Li‐S) batteries have been considered as a promising candidate for next‐generation electrochemical energy‐storage technologies because of their overwhelming advantages in energy density. Suppression of the polysulfide dissolution while maintaining a high sulfur utilization is the main challenge for Li–S batteries. Here, we have designed and synthesized double‐shelled nanocages with two shells of cobalt hydroxide and layered double hydroxides (CH@LDH) as a conceptually new sulfur host for Li–S batteries. Specifically, the hollow CH@LDH polyhedra with complex shell structures not only maximize the advantages of hollow nanostructures for encapsulating a high content of sulfur (75 wt %), but also provide sufficient self‐functionalized surfaces for chemically bonding with polysulfides to suppress their outward dissolution. When evaluated as cathode material for Li–S batteries, the CH@LDH/S composite shows a significantly improved electrochemical performance.     

NLR、hs-CRP、MPV与肥胖、非肥胖型PCOS的关系

目的探究中性粒细胞/淋巴细胞比值（NLR）、超敏C反应蛋白（hs-CRP）、血小板平均体积（MPV）与肥胖、非肥胖型多囊卵巢综合征（PCOS）的关系。方法对112例PCOS患者（肥胖型68例,非肥胖型44例）和年龄、BMI配对的90例健康体检女性（健康对照组肥胖型47例,非肥胖型43例）,检测并比较两组及亚组之间MPV、NLR、hs-CRP、生殖内分泌激素及代谢指标。结果PCOS组血清空腹血糖水平（FPG）、空腹胰岛素（FINS）、稳态胰岛素评价指数（HOMA-IR）、NLR、hs-CRP、MPV水平均明显高于健康对照组（均P＜0.05）。肥胖型PCOS组NLR、hs-CRP、MPV高于肥胖型健康对照组（均P＜0.05）。肥胖型PCOS组NLR、hs-CRP、MPV均高于非肥胖型PCOS组（均P＜0.05）。NLR、hs-CRP、MPV的AUC及95%CI分别为0.819（0.763~0.903）、0.982（0.959~1.000）、0.906（0.848~965）。结论肥胖型PCOS患者血清NLR、hs-CRP、MPV水平明显升高,这些指标的变化对肥胖型PCOS代谢异常有较强的诊断价值。     

Catalyst-Controlled Regiodivergent and Enantioselective Formal Hydroamination of N,N-Disubstituted Acrylamides to α-Tertiary-α-Aminolactam and β-Aminoamide Derivatives

Enantioenriched α-tertiary-α-aminoacid and α-chiral-β-aminoacid derivatives play an important role in biological science and pharmaceutical chemistry. Thus, the development of methods for their synthesis is highly valuable and yet remains challenging. Herein, an unprecedented catalyst-controlled regiodivergent and enantioselective formal hydroamination of N,N-disubstituted acrylamides with aminating agents has been developed, accessing enantioenriched α-tertiary-α-aminolactam and α-chiral-β-aminoamide derivatives. Sterically-disfavored and electronically-disfavored enantioselective hydroamination of electron-deficient alkenes have been successfully tuned using different transition metals and chiral ligands. Notably, extremely hindered aliphatic α-tertiary-α-aminolactam derivatives were synthesized by Cu−H catalyzed asymmetric C−N bond forming with tertiary alkyl species. Enantioenriched α-chiral-β-aminoamide derivatives have been accessed by Ni−H catalyzed anti-Markovnikov-selective formal hydroaminations of alkenes. This set of reactions tolerates a wide range of functional groups to deliver diverse α-tertiary-α-aminolactam and α-chiral-β-aminoamide derivatives in good yields with high levels of enantioselectivity.     

Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries

Layered manganese dioxide is a promising cathode candidate for aqueous Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic conductivity and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K⁺-intercalated δ-MnO₂ nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K⁺ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochemical properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.     

Positive Valent Metal Sites in Electrochemical CO2 Reduction Reaction

The discovery of high-performance catalysts for the electrochemical CO₂ reduction reaction ( CO₂RR) has faced an enormous challenge for years. The lack of cognition about the surface active structures or centers of catalysts in complex conditions limits the development of advanced catalysts for CO₂RR. Recently, the positive valent metal sites (PVMS) are demonstrated as a kind of potential active sites, which can facilitate carbon dioxide (CO₂) activation and conversation but are always unstable under reduction potentials. Many advanced technologies in theory and experiment have been utilized to understand and develop excellent catalysts with PVMS for CO₂RR. Here, we present an introduction of some typical catalysts with PVMS in CO₂RR and give some understanding of the activity and stability for these related catalysts.     

Existence of Optimal Controls for Semilinear Parabolic Equations without Cesari-Type Conditions

Abstract. Optimal control problems governed by semilinear parabolic partial differential equations are considered. No Cesari-type conditions are assumed. By proving the existence theorem and the Pontryagin maximum principle of optimal ``state-control" pairs for the corresponding relaxed problems, an existence theorem of optimal pairs for the original problem is established.     

新型(4-HBA)SbX5·H2O类钙钛矿单晶及其卤素结构对发光特性的调控(英文)

发光材料因其在照明、显示、成像等方面的广泛应用而备受关注。作为新兴发光材料之一,钙钛矿类材料的研究及报道较多。其中,铅基钙钛矿的研究取得了巨大进展,光致发光量子产率(PLQY)几乎达到了100%。然而,基于铅基钙钛矿化学毒性和低稳定性,在实际应用过程中需要特殊的封装,因而提高了生产成本并限制了其实际应用领域。被广泛关注的锡基钙钛矿的荧光量子产率几乎能达到90%,但Sn²⁺易氧化成Sn⁴⁺,在空气中极不稳定。相较于铅基钙钛矿和锡基钙钛矿,锑基钙钛矿的低化学毒性、高热稳定性等优点突出。此外,锑基钙钛矿的光学性能在过去几年中也取得了很大的进展,有望突破传统钙钛矿应用的局限。在此,我们报道了一系列新型单晶(4-HBA)SbX₅·H₂O (4-HBA为4-羟基苄胺缩写,X为Cl或Br)。利用溶剂热法可制备高质量的(4-HBA)SbBr₅·H₂O、(4-HBA)SbBr₃Cl₂·H₂O和(4-HBA)S...     

Characterization of constituents in Stellera chamaejasme L. by rapid-resolution liquid chromatography-diode array detection and electrospray ionization time-of-flight mass spectrometry

A reliable and rapid method based on rapid-resolution liquid chromatography-diode array detection (RRLC-DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS) has been developed for the isolation and characterization of multiple constituents in the root of Stellera chamaejasme L., which was extracted by sonication with methanol in an optimized procedure. Separation of the multiple constituents was achieved on an Agilent Zorbax XDB-C18 (50x3.0 mm i.d.; 1.8 microm) column using a gradient elution at a flow rate of 0.4 mL/min. The detection wavelength was 210 nm. Mass spectra were acquired in both positive and negative modes. A formula database of the known chemical constituents in the root of Stellera chamaejasme L. was established by an Agilent software. Twenty-two obvious peaks appeared in the total ion chromatogram and nine of them were characterized by TOF/MS. The RRLC-DAD and ESI-TOF/MS method with ultrasonic extraction would be useful for rapid and effective characterization of chemical constituents in the root of Stellera chamaejasme L.     

Highly Efficient Regioselective Synthesis of 5′-<Emphasis Type="Italic">O</Emphasis>-lauroyl-5-azacytidine Catalyzed by <Emphasis Type="Italic">Candida antarctica</Emphasis> Lipase B

Enzymatic regioselective acylation of 5-azacytidine with vinyl laurate was successfully conducted with an immobilized lipase from Candida antarctica type B (i.e., Novozym 435) for the first time. The acylation of 5-azacytidine took place at its primary hydroxyl group and the desired product 5′-O -lauroyl-5-azacytidine could be prepared with high reaction rate, high conversion, and excellent regioselectivity. The influences of several key variables on the enzymatic acylation were also systematically examined. Pyridine was found to be the best reaction medium. The optimum initial water activity, the molar ratio of vinyl laurate to 5-azacytidine and reaction temperature were 0.07, 30:1, and 50 °C, respectively. Under the optimized conditions described above, the initial reaction rate, the substrate conversion, and the regioselectivity were as high as 0.58 mM/min, 95.5%, and >99%, respectively, after a reaction time of around 5 h.