Dynamic Variation of Amino Acid Contents and Identification of Sterols in Xinyang Mao Jian Green Tea

As important biomolecules in Camellia sinensis L., amino acids (AAs) are considered to contribute to the overall green tea sensory quality and undergo dynamic changes during growth. However, limited by analytical capacity, detailed AAs composition in different growth stages remains unclear. To address this question, we analyzed the dynamic changes of 23 AAs during leaf growth in Xinyang Mao Jian (XYMJ) green tea. Using amino acid analyzer, we demonstrated that most AAs are abundant on Pure Brightness Day and Grain Rain Day. After Grain Rain, 23 AAs decreased significantly. Further analysis shows that theanine has a high level on the day before Spring Equinox and Grain Rain, accounting for 44–61% of the total free AAs content in tea leaves. Glu, Pro, and Asp are the second most abundant AAs. Additionally, spinasterol and 22,23-dihydrospinasterol are first purified and identified in ethanol extract of XYMJ by silica gel column chromatography method. This study reveals the relationship between plucking days and the dynamic changes of AAs during the growth stage and proves the rationality of the traditional plucking days of XYMJ green tea.     

Quantum limited frequency modulation laser spectroscopy

Frequency modulation spectroscopy (FMS) is an optical heterodyne technique which allows high-resolution, high-sensitivity measurements of absorptions or dispersions associated with narrow spectral features. With new methods, the sensitivity limitations of FMS (caused by residual amplitude modulation) can be overcome, and quantum-limited performance can be readily achieved.     

Raman excitation profiles,fluorescence spectra and excited state proton transfer of solid 1.8 dihydroxyanthraquinone at 8 K

The single crystal fluorescence spectra as well as the Raman spectra and excitation profiles of solid 1.8 dihydroxyanthraquinone have been measured. Four electronic transitions in the visible range were found: a π—π* active in absorption, a Franck—Condon absorption emission active transition and two emissions due to excited state proton and Hatom transferred configurations.     

手性大孔磷酸镓Hit-5的水热合成与晶体结构

本文采用水热合成法制备了一个三维手性大孔开放骨架磷酸镓Ga16P16O75·4[1,6-C6H18N2]·[C2H10N2]·2H2O(简称Hit-5).反应起始原料摩尔配比为:1 GaOOH:15 H3PO4:7.5 H2N(CH2)6NH2:0.5 C2H8N2:555 H2O.Hit-5属正交晶系,P21212空间群,晶胞参数:a=0.8671(1)nm,b=1.7945(1)nm,c=0.9101(1)nm,β=108.33(1)°,V=1.3443(2)nm3,Z=4.Hit-5的骨架是由Ga3P3六聚体和Ga4P4八聚体两个不同的二级结构单元通过共顶点联接构成三维纳米孔结构,在[001]方向呈现16-元环孔道.     

Adversarial Data Hiding in Digital Images

In recent studies of generative adversarial networks (GAN), researchers have attempted to combine adversarial perturbation with data hiding in order to protect the privacy and authenticity of the host image simultaneously. However, most of the studied approaches can only achieve adversarial perturbation through a visible watermark; the quality of the host image is low, and the concealment of data hiding cannot be achieved. In this work, we propose a true data hiding method with adversarial effect for generating high-quality covers. Based on GAN, the data hiding area is selected precisely by limiting the modification strength in order to preserve the fidelity of the image. We devise a genetic algorithm that can explore decision boundaries in an artificially constrained search space to improve the attack effect as well as construct aggressive covert adversarial samples by detecting “sensitive pixels” in ordinary samples to place discontinuous perturbations. The results reveal that the stego-image has good visual quality and attack effect. To the best of our knowledge, this is the first attempt to use covert data hiding to generate adversarial samples based on GAN.     

A C-13 NMR and theoretical study of the electronic structure of acylsilanes

The results of a C-13 NMR study on a series of acylsilanes and carbon analogs are reported. The results are rationalized in terms of a theoretical analysis based on the σ and π charge components of XH₃ and HC&z.dbnd;O moieties.     

Furan ring as masked 3-acylacrylate moiety. Practical synthesis of racemic (E)4,4(ethylenedioxy)-7-hydroxy 2-octenoic acid,the c-8 subunit of pyrenophorin

Furfural and acetone are the starting materials for a new practical synthesis of racemic (E)4,4(ethylenedioxy)-7-hydroxy-2-octenoic acid, the protected C-8 subunit of Pyrenophorin. Furan ring has been used as masked 3-acylacrylate moiety.     

Syntheses and structural studies on picolinoyl,nicotinoyl and isonicotinoyl hydrazone derivatives of dicyclopentadienylzirconium(IV)

The reactions of dicyclopentadienylzirconium(IV) dichloride with picolinoyl, nicotinoyl and isonicotinoyl hydrazones derived from the appropriate acid hydrazides and acetone, acetophenone, salicylaldehyde or o-hydroxyacetophenone, have been studied in anhydrous tetrahydrofuran or dichloromethane in the presence or absence of amine using different molar ratios. Tentative structural coclusions are drawn for the reaction products based upon elemental analysis, electrical conductance, magnetic moment and spectral data (electronic, infrared and ¹H NMR). These ligands behave as neutral or deprotonated chelating agents. The coordination behaviour depends upon the pH of the medium, the nature of the substituent and the position of the hydrazone group relative to the pyridine nitrogen nucleus.     

Na2S-Mediated One-Pot Selective Deoxygenation of α-Hydroxyl Carbonyl Compounds including Natural Products

A practical method for the deoxygenation of α-hydroxyl carbonyl compounds under mild reaction conditions is reported here. The use of cheap and easy-to-handle Na₂S·9H₂O as the reductant in the presence of PPh₃ and N-chlorosuccinimide (NCS) enables the selective dehydroxylation of α-hydroxyl carbonyl compounds, including ketones, esters, amides, imides and nitrile groups. The synthetic utility is demonstrated by the late-stage deoxygenation of bioactive molecule and complex natural products.