Determination of radix ginseng volatile oils at different ages by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Comprehensive 2-D GC (GC x GC) coupled with TOF MS or flame ionization detector (FID) was employed to characterize and quantify the chemical composition of volatile oil in the radixes of Panax ginseng C. A. Mey. (ginseng) at different ages. Thirty-six terpenoids were tentatively identified based on the MS library search and retention index in a ginseng sample at the age of 3 years. An obvious group-type separation was obtained in the GC x GC-TOF MS chromatogram. The data collected by GC x GC-FID were processed using a principal component analysis (PCA) method to classify the samples at different ages. The compounds responsible for the significant differentiation among samples were defined. It was found that the relative abundances of alpha-cadinol, alpha-bisabolol, thujopsene, and n-hexadecanoic acid significantly rise with the increase in age.     

Metabolic fingerprinting investigation of Artemisia annua L. in different stages of development by gas chromatography and gas chromatography-mass spectrometry

Artemisia annua L. is an annual herb native of Asia and this plant has been famous for the discovery of the anti-malarial drug artemisinin since 1971. In this work, to investigate variety of whole metabolites, metabolic fingerprinting analysis of A. annua L. was carried out by GC and GC-MS coupled with trimethylsilyl derivatisation. Principal component analysis and partial least squares discriminant analysis were employed to classify GC data of A. annua L. samples at five developmental stages. The results indicated that there was no distinct difference of metabolites between control (001) and transgenic strain (F4) from the tender seedling stage to adult seedling stage, but clear differences were detected at pre-flower budding stage, flower budding stage and full flowering stage. Three precursors of artemisinin biosynthesis were studied at five developmental stages and found that a possible bottleneck exists in the conversion from artemisinic acid or dihydroartemisinic acid to artemisinin.     

Host–Guest Doping in Flexible Organic Crystals for Room-Temperature Phosphorescence

Organic single crystals (OSCs) with excellent flexibility and unique optical properties are of great importance due to their broad applicability in optical/optoelectronic devices and sensors. Nevertheless, fabricating flexible OSCs with room-temperature phosphorescence (RTP) remains a great challenge. Herein, we propose a host–guest doping strategy to achieve both RTP and flexibility of OSCs. The single-stranded crystal is highly bendable upon external force application and can immediately return to its original straight shape after removal of the stress, impressively emitting bright deep-red phosphorescence. The theoretical and experimental results demonstrate that the bright RTP arises from Förster resonance energy transfer (FRET) from the triphenylene molecules to the dopants. This strategy is both conceptually and synthetically simple and offers a universal approach for the preparation of flexible OSCs with RTP.     

Influence of laser mode on splitting beam illumination effect of Dammann grating

The influences of various laser modes on the splitting beam effect of Dammann grating are studied in theory and by numerical simulation. The results show that fundamental mode laser resembles plane wave while high order mode laser differs from plane wave in the splitting beam effect by Dammann grating. Therefore, the fundamental mode laser is more suitable to be the light source to improve the energy efficiency in far-distance image detecting systems, such as laser image ladar, which use Dammann grating in the ilhlmination svstem.     

Blue‐Emissive Cobalt(III) Complexes and Their Use in the Photocatalytic Trifluoromethylation of Polycyclic Aromatic Hydrocarbons

Room‐temperature luminescent Co^III complexes ( 1 and 2 ) are presented that exhibit intense ligand‐to‐metal and ligand‐to‐ligand charge transfer absorption in the low‐energy UV region (λ_abs≈360–400 nm) and low‐negative quasi‐reversible reduction events (E^1/2_(red)=?0.58 V and ?0.39 V vs. SCE for 1 and 2 , respectively). The blue emission of 1 and 2 at RT is due to the large bite angles and strong σ‐donation of the ligands, the combined effect of which helps to separate the emissive ³LMCT (triplet ligand‐to‐metal charge transfer) and the non‐emissive ³MC (triplet metal‐centered) states. 1 and 2 were found to be powerful photo‐oxidants (E =2.26 V and 2.75 V vs. SCE of 1 and 2 , respectively) and were used as inexpensive photoredox catalysts for the regioselective mono(trifluoromethylation) of polycyclic aromatic hydrocarbons (PAHs) in good yields (ca. 40–58 %).     

稳态强磁场实验装置水冷系统水耗分析及回用设计

稳态强磁场实验装置水冷系统主要用于带走大功率水冷磁体运行过程中所产生的热量. 为了防止水中的离子导电, 磁体循环冷却水采用去离子水, 因此水冷系统配备了10 m3/h 的去离子水制备系统及65 m3/h 的提纯系统, 以保障循环水水质的高稳定性. 磁体循环冷却水的热量通过板式换热器由低温冷冻水带走. 系统在纯水制备及提纯过程中存在排水量大, 排水水质高等特征, 而在冷冻水制备过程中则存在较高的冷却水蒸发损失. 本文结合系统特征对其各环节排水量及其水质等进行了分析, 得出了该类型水冷系统的水耗特征及系统日均水耗. 结合水质, 对纯水系统的主要排水进行了回用方案分析并通过计算得出了最大回用率.     

Multipulse gate-delayed range gating imaging lidar

We present a technique to reconstruct a higher resolution of depth map of range gating imaging lidar by applying the delays of the gates to a typical range gating lidar system during the detection of each returned laser pulse with the encoding of the returned signal. With the consequent delays of the gate, the depth of the scene is extended accordingly. A multipulse gate-delayed range gating lidar system is designed to prove the resolution improvement from 6 to 1.5 m. The unchanged peak power of the laser, the widths of the laser pulse and the sampling period result in a simple structure of the lidar system.     

Highly Acidic Conjugate‐Base‐Stabilized Carboxylic Acids Catalyze Enantioselective oxa‐Pictet–Spengler Reactions with Ketals

Acyclic ketone‐derived oxocarbenium ions are involved as intermediates in numerous reactions that provide valuable products, however, they have thus far eluded efforts aimed at asymmetric catalysis. We report that a readily accessible chiral carboxylic acid catalyst exerts control over asymmetric cyclizations of acyclic ketone‐derived trisubstituted oxocarbenium ions, thereby providing access to highly enantioenriched dihydropyran products containing a tetrasubstituted stereogenic center. The high acidity of the carboxylic acid catalyst, which exceeds that of the well‐known chiral phosphoric acid catalyst TRIP, is largely derived from stabilization of the carboxylate conjugate base through intramolecular anion‐binding to a thiourea site.     

Pd/Ni Co-catalyzed Selective Cross-Coupling of Aryl Bromides and Aryl Fluorosulfonates at Room Temperature

Multimetallic catalysis can effectively enhance the selectivity for the heterocoupling product over homocoupling products in cross-electrophilic couplings. We report the selective cross-coupling of aryl bromides with aryl fluorosulfonates via palladium and nickel cooperative catalysis for the synthesis of biaryls, which can be carried out at room temperature while having marvelous chemoselectivity. In addition, the reaction also has a good performance on the gram-scale reaction.