Palladium-catalyzed chemoselective direct α-arylation of carbonyl compounds with chloroaryl triflates at the C–Cl site

This study described palladium-catalyzed chemoselective direct α-arylation of carbonyl compounds with chloroaryl triflates in the Ar–Cl bond. The Pd/SelectPhos system showed excellent chemoselectivity toward the Ar–Cl bond in the presence of the Ar–OTf bond with a broad substrate scope and excellent product yields. The electronic and steric hindrance offered by the –PR₂ group of the ligand with the C2-alkyl group was found to be the key factor affecting the reactivity and chemoselectivity of the α-arylation reaction. The chemodivergent approach was also successfully employed in the synthesis of flurbiprofen and its derivatives (e.g., –OMe and –F).

Palladium-catalyzed chemoselective direct α-arylation of carbonyl compounds with chloroaryl triflates in the Ar–Cl bond is reported. The effects of –PR₂ and C2-alkyl groups of the ligands are investigated using experimental and computational methods.     

Responses of Issatchenkia terricola WJL-G4 upon Citric Acid Stress

This study aimed to elucidate the responses of a novel characterized Issatchenkia terricola WJL-G4 against citric acid stress by performing physiological analysis, morphology observation, and structural and membrane fatty acid composition analysis. The results showed that under citric acid stress, the cell vitality of I. terricola WJL-G4 was reduced. The cell morphology changed with the unclear, uncompleted and thinner cell wall, and degraded the cell structure. When the citric acid concentration was 20 g/L, I. terricola WJL-G4 could tolerate citric acid and maintain the cell structure by increasing the intracellular pH, superoxide dismutase activity, and contents of unsaturated fatty acids. As the citric acid concentration was ≥80 g/L, the stress has exceeded the cellular anti-stress ability, causing substantial cell damage. The cell membrane permeability, the content of membrane lipids, malondialdehyde and superoxide anion increased, but the intracellular pH and superoxide dismutase activities decreased, accompanying the increase of citric acid concentrations. The findings of this work provided a theoretical basis for the responsive mechanism of I. terricola WJL-G4 under high concentrations of citric acid, and can serve as a reference for biological acid reduction in fruit processing.     

Discriminant Analysis of the Nutritional Components between Organic Eggs and Conventional Eggs: A 1H NMR-Based Metabolomics Study

The difference of nutrient composition between organic eggs and conventional eggs has always been a concern of people. In this study, ¹H nuclear magnetic resonance (NMR) technique combined with multivariate statistical analyses was conducted to identify the metabolite different in egg yolk and egg white in order to reveal the nutritional components information between organic and conventional eggs. The results showed that the nutrient content and composition characteristics were different between organic and conventional eggs, among which the content of glucose, putrescine, amino acids and their derivatives were found higher in the organic eggs yolk, while phospholipids were demonstrated higher in conventional eggs yolk. Organic acid, alcohol, amine, choline and amino acids were higher in conventional eggs white, but glucose and lactate in organic egg were higher. Our study demonstrated that there are more nutritive components and higher nutritional value in organic eggs than conventional eggs, especially for the growth and development of infants and young children, and conventional eggs have more advantages in promoting lipid metabolism, preventing fatty liver, and reducing serum cholesterol. Eggs have important nutritional value to human body, and these two kinds of eggs can be selected according to the actual nutrient needs.     

Rapid Detection of Five Estrogens Added Illegally to Dietary Supplements by Combining TLC with Raman Imaging Microscope

Estrogens added illegally to dietary supplements are hazardous to human health. Traditional detection and analysis methods have many limitations, and we have developed an assay that combines thin-layer chromatography with Raman imaging microscopy (TLC-RIM). The five estrogens (estrone, estradiol, estriol, ethinyl estradiol, and diethylstilbestrol) were initially separated by TLC, then detected by area scanning Raman imaging with a 532 nm laser under a microscope. Raman spectra were obtained for each estrogen, which were used for detecting estrogen illegally added to botanical dietary supplements. The LOD of each estrogen was 0.4, 1.0, 0.8, 0.2, and 0.2 mg/mL, respectively. The matrix in the real sample did not interfere with the detection of estrogens. The method was fast, sensitive, stable, specific, and reliable.     

Impact of the Acetaldehyde-Mediated Condensation on the Phenolic Composition and Antioxidant Activity of Vitis vinifera L. Cv. Merlot Wine

Acetaldehyde is a critical reactant on modifying the phenolic profile during red wine aging, suggesting that the acetaldehyde-mediated condensation can be responsible for the variation of antioxidant activity during the aging of this beverage. The present study employs exogenous acetaldehyde at six levels of treatment (7.86 ± 0.10–259.02 ± 4.95 mg/L) before the bottle aging of Merlot wines to encourage phenolic modification. Acetaldehyde and antioxidant activity of wine were evaluated at 0, 15, 30, 45, 60 and 75 days of storage, while monomeric and polymeric phenolics were analyzed at 0, 30 and 75 days of storage. The loss of acetaldehyde was fitted to a first-order reaction model, the rate constant (k) demonstrated that different chemical reaction happened in wines containing a different initial acetaldehyde. The disappearance of monomeric phenolics and the formation of polymeric phenolics induced by acetaldehyde could be divided into two phases, the antioxidant activity of wine did not alter significantly in the first phase, although most monomeric phenolics vanished, but the second phase would dramatically reduce the antioxidant activity of wine. Furthermore, a higher level of acetaldehyde could shorten the reaction time of the first phase. These results indicate that careful vinification handling aiming at controlling the acetaldehyde allows one to maintain prolonged biological activity during wine aging.     

Asymmetric conductivity of the Kondo effect in cold atomic systems

Motivated by recent theoretical and experimental advances in quantum simulations using alkaline earth(AE)atoms,we put forward a proposal to detect the Kondo physics in a cold atomic system.It has been demonstrated that the intrinsic spin-exchange interaction in AE atoms can be significantly enhanced near a confinement-induced resonance(CIR),which facilitates the simulation of Kondo physics.Since the Kondo effect appears only for antiferromagnetic coupling,we find that the conductivity of such system exhibits an asymmetry across a resonance of spin-exchange interaction.The asymmetric conductivity can serve as the smoking gun evidence for Kondo physics in the cold atom context.When an extra magnetic field ramps up,the spin-exchange process near Fermi surface is suppressed by Zee-man energy and the conductivity becomes more and more symmetric.Our results can be verified in the current experimental setup.     

L波段高功率线极化径向线阵列天线理论分析与数值模拟

 探索了L波段的高功率线极化径向线阵列天线。基于三角形栅格形式实现了径向线圆形平面阵列天线,分析并给出了径向线并联馈电网络,并以同轴馈电的水平单圆环线极化天线为基础,利用径向线并联馈电网络设计出了间距小于一个波长下L波段高功率线极化径向线阵列天线。研究结果表明：这种结构实现径向线阵列天线的线极化辐射是可行的,该天线在中心频率1.57 GHz下,增益为19.97 dBi,轴比为-52.06 dB,反射系数为0.105 2;在1.37～1.77 GHz的频率范围内增益大于18.64 dBi,轴向轴比值小于-46.45 dB。     

CeO_2和Y_2Ba_1Cu_1O_(5-δ)共同掺杂对Y_1Ba_2Cu_3O_(7-δ)的超导电性及其晶格结构的影响

采用固相反应法成功制备出一批Y123与Y211的摩尔比为1∶0.47的混合物,并在此混合物的基础上掺入CeO2,掺入的比例x分别为0.5wt%、1.0wt%、2.0wt%、3.0wt%、4.0wt%。采用了X-射线衍射仪对样品的晶格结构进行了分析,测量结果表明:x=1.0wt%时掺杂效果最好,同时也充分说明Y123的晶格结构与其超导电性之间存在着一种内在的必然关联。并通过对其测试临界转变温度以及转变宽度,测量结果也充分验证了上述结论。     

Improvement of the Performance of an Acousto-Optical Q-Switched Nd:YAG 946 nm Laser Using a Convex–Plane Cavity

We improve the performance of an acousto-optical Q-switched Nd:YAG 946 nm laser using a convex–plane cavity. We obtain the highest output average power of 2.3 W with a pulse width of 15.3 ns in a 10 kHz 946 nm laser with a convex–plane cavity. The maximum peak power 15.0 kW is about three times higher than that in a plane–plane cavity. Also we investigate the output performances of the pulsed 946 nm laser with the convex–plane cavity at 20 and 50 kHz.