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Background: Over recent decades, sulfur fumigation is becoming abused in processing some freshly harvested herbs used as both medicine and food, although it has been questioned whether sulfur fumigation will change the efficacy and safety of the herbs. One of the herbs commonly processed by sulfur fumigation is Platycodonis Radix (Jiegeng in Chinese). Glycosides are the main bioactive components of Jiegeng. Up to the present, no study has been carried out to evaluate the impact of sulfur fumigation on glycoside profile ofJiegeng. Methods: A rapid and versatile ultra-high performance liquid chromatography coupled with ultra-high resolution quadrupole time-of-flight mass spectrometry (LJHPLC UHD Q-TOF MS/MS) method was developed for comprehensive analysis of the glycoside profiles of sulfur-fumigated and air-dried Jiegeng samples. Results: Twenty-three glycosides were detected in air-dried and sulfur-fumigated Jiegeng samples. After sulfur fumigation, the peak heights of eight glycosides, namely platycogenin A, platycodin D, platycodin D2, platycodin D3, polygalacin D, polygalacin D2, deapio-platycodin D and 3"-O-acetylplatycodin D2, remarkably decreased; while peak heights of five glycosides, namely syringin, lobetyolin, platycoside E, deapio-platycodin D2 and deapio-platycoside E, slightly increased; in addition, peaks often glycosides, platycodin A, platycodin C, platycodin V, platycoside C, 16-oxo-platycodin D, 2"-O-acetylpolygalacin D, 2"-O-acetylpolygalacin D2, 3"-O-acetylpolygalacin D, 3"-O-acetylpolygalacin D2, and platycogenic acid B, disappeared. Conclusion: Sulfur fumigation caused significant changes of glycoside components of Jiegeng. Further investigations are warranted to explore how these chemical changes occurred and whether these changes would affect the efficacy and safety of Jiegeng. [ABSTRACT FROM AUTHOR]

A Be δ-doped GaAs/AlAs three quantum wells emitter in the terahertz range is fabricated and electroluminescence is investigated. An electroluminescence peak centered at 23.4 meV with a full width at half maximum of 4.2 meV is observed under a bias of 2 V at low temperature (T=4.5 K). The emission peak is attributed to the 2p to 1s internal transitions of the Be acceptors in the center of δ-doped GaAs quantum well. The current-voltage characteristics of the device measured at different temperatures demonstrate a strong negative differential resistance and temperature dependence. [ABSTRACT FROM AUTHOR]

A series of GaAs/AlAs multiple-quantum wells doped with Be is grown by molecular beam epitaxy. The photoluminescence spectra are measured at 4, 20, 40, 80, 120, and 200 K, respectively. The recombination transition emission of heavy-hole and light-hole free excitons is clearly observed and the transition energies are measured with different quantum well widths. In addition, a theoretical model of excitonic states in the quantum wells is used, in which the symmetry of the component of the exciton wave function representing the relative motion is allowed to vary between the two- and three-dimensional limits. Then, within the effective mass and envelope function approximation, the recombination transition energies of the heavy- and light-hole excitons in GaAs/AlAs multiple-quantum wells are calculated each as a function of quantum well width by the shooting method and variational principle with two variational parameters. The results show that the excitons are neither 2D nor 3D like, but are in between in character and that the theoretical calculation is in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

In this letter, a wideband and low‐profile multipolarization reconfigurable antenna based on metasurface (MTS) is proposed. The antenna mainly contains two parts, an upper layer of MTS and a bottom layer of circular slot antenna. The MTS acts as a polarization controller, by mechanically rotating the MTS layer at a proper angle while keeping the circular slot antenna remain stationary, the polarization mode of the antenna can be switched to linear polarization (LP), left‐hand circular polarization (LHCP), and right‐hand circular polarization (RHCP). The experimented −10 dB impedance bandwidth of 37.8% and 54% for LP and circular polarization (CP) modes, respectively. The measured overlapped 3‐dB AR bandwidth is 22.2% for both CP modes, covering from 3.2 to 4 GHz. Moreover, the measured peak gain of the presented antenna reaches 9 dBi and 8 dBic for LP and CP modes, with a lower profile of 0.05 λ0. [ABSTRACT FROM AUTHOR]

Demand for low-input nitrogen sustainable rice is increasing to meet the need for environmentally friendly agriculture and thus development of rice with high nitrogen use efficiency (NUE) is a major objective. Hence, understanding how rice responds to growth under low-nitrogen conditions is essential to devise new ways of manipulating genes to improve rice NUE. In this study, using two rice varieties with different seedling-stage NUE obtained from previous field experiments, we investigated the physiological and molecular responses of young rice to low-nitrogen conditions. Our results suggest that glutamine synthetase (GS) and NADH-dependent glutamate synthase (NADH-GOGAT) play important roles in N assimilation of seedling rice roots under low-nitrogen conditions; the regulatory mechanisms of GS and NADH-GOGAT in seedling rice roots do not occur at the transcription level, and may be posttranscriptional; OsAMT1;1 play important roles in rice N acquisition by partially regulating N uptake under low-nitrogen conditions; and OsAMT1;1 and OsNRT2;1 also play important roles in rice N acquisition by partially regulating root growth and development under low-nitrogen conditions. The challenge for future studies is to characterize the functional roles of GS, NADH-GOGAT, OsAMT1;1, and OsNRT2;1 in young rice NUE using RNAi and mutant techniques. [ABSTRACT FROM AUTHOR]

Three samples of GaAs/AlAs multiple-quantum wells with different quantum well widths and δ-doped with Be acceptors at the well center were grown on (100) GaAs substrates by molecular beam epitaxy. Polarized Raman spectra were recorded on the three samples at temperatures in a range of 4–50 K in a backscattering configuration. The two branches of coupled modes due to the interaction of the hole intersubband transitions and the quantum-well longitudinal optical (LO) phonon were observed clearly. The evaluation formalism of the Green function was employed and each lineshape of the Raman spectrum of the coupled modes was simulated. The dependence of the peak position of Raman shifts of the two coupled modes as well as the quantum-well LO phonon on the quantum-well size and measured temperature were given, and the coupling interaction mechanism between the hole subband transitions and the quantum-well LO phonon was researched. [ABSTRACT FROM AUTHOR]

Chloroform (AGC), ethyl acetate (AGE) and n-butanol (AGB) extracts of Abies georgei were investigated for anti-tumour and anti-inflammatory activities in-vitro and in-vivo. AGC exhibited potent antiproliferative effects against A549, LOVO, QGY-7703 and 6T-CEM tumour cells, with EC50 values of 77.5, 7.8, 11.1 and 32.8 μgmL−1, respectively. It also inhibited the growth of S180 sarcoma implanted into mice; tumour growth inhibition ratios were 46.7, 53.1 and 31.0% of controls at doses of 100, 200 and 400 mgkg−1, respectively. AGE showed significant anti-inflammatory activities in the carrageenin-induced acute pedal oedema model in rats and dimethylbenzene-induced ear oedema in mice at doses of 140 mgkg−1 and 200 mgkg−1 p.o., respectively. Primary mechanism studies in-vitro showed that AGE inhibited platelet aggregation induced in rabbits by arachidonic acid (AA), with an IC50 of 14.4 μgmL−1. Its effect on AA metabolism was also studied in mouse peritoneal macrophages stimulated by A23187. Formation of prostaglandin E2, leukotriene B4 and 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE) was significantly inhibited in a concentration-dependent manner. In addition, AGE inhibited lipopolysaccharide-induced nitric oxide production in RAW246.7 macrophages and nuclear factor κB activation induced in 293 cells by tumour necrosis factor α. [ABSTRACT FROM AUTHOR]

Cycloabiesesquine A, representing a unique carbon skeleton among the sesquiterpenoids, was isolated from Abies delavayi and by extensive spectroscopic and computational methods, its structure was elucidated as (7S,8R,12R)-4,8-dihydroxy-1,3,5,10-tetraen-8,12-cyclobisabolan-9-one. [ABSTRACT FROM AUTHOR]