Comprehensive comparison of aroma profiles and chiral free and glycosidically bound volatiles in Fujian and Yunnan white teas.

The Fujian and Yunnan provinces in China are the most representative origins of white tea. However, the key differences in the chemical constituents of the two white teas have rarely been revealed. In this study, a comprehensive comparison of the aroma profiles, chiral volatiles, and glycosidically bound volatiles (GBVs) in Fujian and Yunnan white teas was performed, and 174 volatiles and 28 enantiomers, including 22 volatiles and six GBVs, were identified. Linalool, linalyl-ß-primeveroside (LinPrim), and α-terpineol presented the opposite dominant configurations in Fujian and Yunnan white teas, and the chiral GBVs were firstly quantified with significant differences in the contents of R-LinPrim and ß-d-glucopyranosides of (2R, 5R)-linalool oxide A and (2R, 5S)-linalool oxide B. Moreover, discrimination functions for Fujian and Yunnan white teas were created using nine key variables with excellent reliability and efficiency. These results provide a new method for objectively distinguishing authentic white teas according to geographical origin.

Research on the influence of power frequency magnetic field of pantograph on pacemaker wearers' health in high-speed EMU.

When the popular means of transportation-high-speed trains meet the increasing rate of pacemaker implantation year by year, the research on the magnetic field environment on the health of pacemaker wearers in the carriage becomes an urgent problem. In this work, models of an electric multiple unit carriage with a pantograph as well as passengers with pacemakers were built by using COMSOL Multiphysics software. The B, Ein and Jin of human heart and other tissues, and the induced voltage (Vin) at the pacemaker electrode were calculated under the pantograph operating condition, so as to assess the effect of its magnetic field on the health of pacemaker wearers. The results showed that Bmax in the carriage without passengers is 121.246 µT, occurs near the window. In the carriage, the Bmax, Ein max and Jin max of heart and body, Vin at the pacemaker electrode of the passenger next to the window are greater than that in the middle of the carriage. The Bmax, Ein max and Jin max of passengers' heart are 11.301µT, 1.613 mV/m and 139.030 µA/m2, respectively. The Bmax, Ein max and Jin max of passengers' body are 12.597µT, 0.788 mV/m and 75.299 µA/m2, respectively. The maximum value of Vin at the tip of the pacemaker electrode of the passengers' is 0.048 mV. The Bmax, Ein max in all tissues of passengers are much smaller than the basic limits of electromagnetic exposure to the public set by the International Commission on Non-Ionizing Radiation. Vin at the electrode tip of passengers' pacemakers are less than the perception sensitivity set by the International Organization for Standardization. This work illustrated that the magnetic field generated by the pantograph is within the recognized accepted limits for passengers with pacemakers, but we still recommended that passengers wearing pacemakers should stay as far away from windows as possible.

Comparative study on ignition delay time and burning rate of modified double-base propellant and fuel-rich propellant.

With the higher requirements of various tactical and technical indicators of the weapon systems, the current research on the ignition and combustion characteristics of different types of solid propellants is not comprehensive. In more complex and harsh environmental conditions, the pressure affects the ignition and combustion characteristics. Therefore, the paper studies the ignition and combustion characteristics of the modified double-base propellants (MDB propellants) and fuel-rich propellants (FR propellants) under low-pressure environment. Combining experiment and theory, the ignition delay time and burning rate of two kinds of solid propellants are compared and analyzed at low pressure by the laser ignition experimental device. The results displayed that the burning flames of the FR and MDB propellant presented evident V-shape and cylindrical, respectively. The flame brightness decreased with the decrease in pressure. With the increase of pressure and heat flux, the ignition delay time of the MDB propellant and the FR propellant decreased. By comparison, Model 2 of the ignition delay time was more effective for the estimation of the ignition delay time of the FR propellant. The experimental results are compared with the three burning rate models, which are the Vielle formula (Model 1), Summerfield formula (Model 2), and B-number burning rate formula (Model 3). The results showed the burning rate was more in accord with Model 3.

Enantiomeric separation and precise quantification of chiral volatiles in Wuyi rock teas using an efficient enantioselective GC × GC-TOFMS approach.

Chiral volatiles play important roles in the formation of aroma quality of foods. To date, enantiomeric characteristics of chiral volatiles in Wuyi rock tea (WRT) and their aroma contributions are still unclear. In this study, an efficient enantioselective comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (Es-GC × GC-TOFMS) approach to separate and precisely quantitate 24 pairs of chiral volatiles in WRTs was established, and the enantiomeric distribution and aroma contribution of chiral volatiles among WRTs from four representative cultivars were investigated. Enantiomeric ratio (ER) of R-α-ionone (80%) in Dahongpao (DHP), ER of S-α-terpineol (57%) in Jinfo (JF), ERs of R-γ-heptanolactone (69%), S-γ-nonanolactone (55%), (2R, 5S)-theaspirane B (91%), concentration of S-(E)-nerolidol (313.37 ng/mL) in Rougui (RG) and concentration of R-α-ionone (33.01 ng/mL) in Shuixian (SX) were unique from other types of WRTs, which were considered as the potential chemical markers to distinguish WRT cultivars. The OAV assessment determined 7 volatile enantiomers as the aroma-active compounds, especially R-α-ionone and R-δ-octanolactone in SX, as well as S-(E)-nerolidol and (1R, 2R)-methyl jasmonate in RG contribute much to aroma formation of the corresponding WRTs. The above results provide scientific references for discrimination of tea cultivars and directed improvement of the aroma quality of WRT.

The complete mitochondrial genome of a marine triclad Miroplana shenzhensis (Platyhelminthes, Tricladida, Maricola).

The complete mitochondrial genome (mitogenome) of Miroplana shenzhensis Yu & Wang, 2013 is reported in the present study, representing the second mitogenome recorded in the suborder Maricola. The circular mitogenome is 14,344 bp in length, containing 12 protein-coding genes, 2 ribosomal RNAs and 22 transfer RNAs. Comparative analysis on mitochondrial gene order reveals a rearrangement in the suborder Maricola, indicating that mitochondrial gene order is conserved only in Continenticola, and is divergent across Tricladida. Phylogenetic analysis shows M. shenzhensis is clustered with an another marine triclad, forming a well-supported monophyletic group of Maricloan.

MitoFlex: an efficient, high-performance toolkit for animal mitogenome assembly, annotation and visualization.

SUMMARY: MitoFlex is a linux-based mitochondrial genome analysis toolkit, which provides a complete workflow of raw data filtering, de novo assembly, mitochondrial genome identification and annotation for animal High Throughput Sequencing data. The overall performance was compared between MitoFlex and its analogue MitoZ, in terms of protein-coding gene recovery, memory consumption and processing speed. AVAILABILITYAND IMPLEMENTATION: MitoFlex is available at https://github.com/Prunoideae/MitoFlex under GPLv3 license. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Two new species of marine flatworm from southern China facilitate determination of the phylogenetic position of the genus Nerpa Marcus, 1948 and the histochemical structure of the nervous system in the genus Paucumara Sluys, 1989 (Platyhelminthes, Tricladida, Maricola).

Two new species of flatworm, collected from a beach at eastern Shenzhen, China, were studied through an integrative approach by combining morphological, histological, histochemical (acetylcholinesterase, AChE), and molecular (18S r- DNA) data. These species belong to two genera of marine triclads, previously unrecorded from China, viz. Nerpa Marcus, 1948 and Paucumara Sluys, 1989.        Nerpa fistulata Wang Chen, sp. nov. is characterized by: transparent body; principally pentamerous intestine with three distinct commissures; two very large, prepharyngeal testis follicles; a semi-circular lens in each eye cup; a penis papilla provided with a chitinized, pointed stylet; lateral bursae communicating with the oviduct and opening ventrally to the exterior via a duct. Phylogenetically N. fistulata groups with one member of the family Bdellouridae. This new, Chinese species of Nerpa introduces a major geographic disjunction, as the type species N. evelinae was described from the bay of Santos, Brazil, so that the genus is now known from both Atlantic as well as Pacific coasts.        The species Paucumara falcata Wang Li, sp. nov. is characterized by: three distinct pale yellow transverse pigmentation bands on its dorsal side, between which some snowflake-like specks are randomly distributed, and a brown transverse band anteriorly to the eyes; 8-11 testicular follicles on either side of the body, the follicles extending from immediately behind the ovaries to half-way along the pharyngeal pocket; a musculo-parenchymatic organ with a sclerotic, curved tip projecting from the anterior wall of the male atrium, ventrally to the root of the penis papilla. Phylogenetically P. falcata groups with its congener P. trigonocephala, with the genus Paucumara forming the sister taxon of the genus Ectoplana. Comparison of the nerve structure of P. falcata, as revealed by AChE histochemistry, with that of eight other species of triclad suggested that the nervous system of marine planarians is simpler than that of species of freshwater planarians, but revealed also that the nerve structure is rather variable among species.        The copulatory position exhibited by two partners in Paucumara falcata is remarkable in that they intertwine, with their heads pointing downwards and the tails pointing upwards, the entire process lasting about 10 min. Such a copulatory position has never before been reported for triclad flatworms.

[Sperm sorting based on the imitation of the physiological process on the microfluidic chip].

OBJECTIVE: To establish a new method for sperm sorting by imitating the physiological process of sperm-cervical mucus interaction on the microfluidic chip. METHODS: We designed a microfluidic chip to imitate the physiological process of natural sperm sorting in the microchannel based on the interaction between sperm and cervical mucus, and obtained motile sperm after the interaction. Meanwhile, we established an integrated real-time sperm detection reservoir on this chip to determine sperm parameters using the computer-assisted sperm analysis system. We analyzed 30 samples using both microfluidic and swim-up methods, and compared the results with those obtained before sorting. RESULTS: The rate of grade a + b sperm, the rate of morphologically normal sperm, straight-line velocity (VSL), average path velocity (VAP) and straightness (STR) were (29.78 +/- 11.24)%, (8.00 +/- 5.19)%, (18.89 +/- 4.90) microm/s, (26.84 +/- 5.13) microm/s and (70.15 +/- 7.61)%, respectively, before sorting, (71.65 +/- 11.18)%, (14.95 +/- 6.79)%, (24.14 +/- 5.95) microm/s, (32.61 +/- 6.36) microm/s and (73.87 +/- 9.34)%, respectively, after swim-up sorting, and (92.37 +/- 6.33)%, (23.33 +/- 7.67)%, (34.03 +/- 16.78) microm/s, (38.73 +/- 16.40) microm/s and (84.91 +/- 12.56)%, respectively, after sorting on the microfluidic chip. The sperm parameters obtained before sorting showed statistically significant differences from those obtained on the chip (P < 0.01) and by the swim-up method (P < 0.05). CONCLUSION: Imitation of the physiological interaction between sperm and cervical mucus on the microfluidic chip helped the realization of both the natural sorting and real-time analysis of sperm. The quality of the sperm sorted on the microfluidic chip is significantly better than that of the sperm before sorting and sorted by the swim-up method. This has prepared the ground for imitating the fertilization process under the physiological condition on the microfluidic chip.