Urinary metabonomics of stomach cancer assessed by rapid resolution liquid chromatography/time-of-flight mass spectrometry

Background Stomach cancer is among the most commonly occurring malignancies worldwide. It would be beneficial to develop a urine-based assay whereby patients with undiagnosed stomach cancer could be screened and their cancer detected in the eadiest stages. Methods A urinary metabonomics method based on ultra-performance liquid chromatography combined with quadruple time-of-flight mass spectrometry was used to analyze urine samples from patients with stomach cancer and healthy controls. Results Statistical analysis revealed a clear separation of patients and healthy controls using the aforementioned methodology. Some significantly changed metabolites were identified. Conclusions Use of the metabonomics method in patients with stomach cancer could effectively detect distinct changes in urinary metabolites and had the capacity to detect cancer; therefore, it may be a valuable tool in earlier diagnosis. Furthermore, the detection and identification of altered metabolites in the current study may help elucidate possible mechanisms involved in stomach cancer.

Rapid Quantification of Chinese Medicine Zuo Jin Pill via RRLC

A rapid method based on rapid resolution liquid chromatography（RRLC） coupled with a diode array detector（DAD） was developed for the simultaneous determination of six major constituents（magnoflorine,jatrorrhizine,coptisine,palmatine,berberine and evodiamine） in traditional Chinese medicine（TCM） Zuo Jin Pill（ZJP）.The satisfactory chromatographic separation was carried on an Eclipse Plus C18 column（1.8 μm i.d.,150 mm×4.6 mm） by linear gradient elution with a mobile phase of acetonitrile-acetate buffer.All the calibration curves show good linearity（r2 0.9998）.The detection limits and quantification limits ranged in 1.4―12 ng and 4.8―30 ng,respectively.The intra-and inter-day precisions were less than 0.63% with accuracies 98.60%―100.78%,and the recoveries were from 99.45% to 100.46%.Furthermore,hierarchical cluster analysis（HCA） was used to evaluate the variation of the herbal prescription.The results demonstrate that this analytical method is simple,sensitive and reliable for rapidly analyzing six major bioactive compounds in ZJPs and is helpful to comprehensively evaluating the quality of this TCM.

Performance analysis of frequency‑mixed PPP‑RTK using low‑cost GNSS chipset with different antenna configurations

Low-cost Global Navigation Satellite System(GNSS)devices offer a cost-effective alternative to traditional GNSS systems,making GNSS technology accessible to a wider range of applications.Nevertheless,low-cost GNSS devices often face the challenges in effectively capturing and tracking satellite signals,which leads to losing the observations at certain frequencies.Moreover,the observation peculiarities of low-cost devices are in contradistinction to those of traditional geodetic GNSS receivers.In this contribution,a low-cost PPP-RTK model that considers the unique characteristics of different types of measurements is developed and its performance is fully evaluated with u-blox F9P receivers equipped with three distinctive antenna configurations:vertical dipole,microstrip patch,and helix antennas.Several static and kinematic experiments in different scenarios are conducted to verify the effectiveness of the proposed method.The results indicate that the mixed-frequency PPP-RTK model outperforms the traditional dual-frequency one with higher positioning accuracy and fixing percentage.Among the three low-cost antennas tested,the vertical dipole antenna demonstrates the best performance under static conditions and shows a comparable performance as geodetic antennas with a positioning accuracy of 0.02 m,0.01 m and 0.07 m in the east,north,and up components,respectively.Under low-speed kinematic scenarios,the helix antenna outperforms the other two with a positioning accuracy of(0.07 m,0.07 m,0.34 m).Furthermore,the helix antenna is also proved to be the best choice for vehicle navigation with an ambiguity fixing rate of over 95%and a positioning accuracy of(0.13 m,0.14 m,0.36 m).

Trace determination of hexabromocyclododecane diastereomers in water samples with temperature controlled ionic liquid dispersive liquid phase microextraction

A novel temperature controlled ionic liquid dispersive liquid phase microextracfion （TCIL-DLPME） coupled with rapid resolution liquid chromatography-electrospray tandem mass spectrometry （RRLC-ESI-MS-MS） has been developed for the enrichment and determination of three hexabromocyclododecane diastereomers （HBCDs） in water samples. Green solvent ionic liquid （IL） was used as extraction solvent instead of toxic organic solvents. This technique also avoided the usage of dispersive solvent. Some important parameters that might affect the extraction efficiency were optimized. Under the optimum conditions, good linear relationship, sensitivity and reproducibility were obtained. All the limits of detection for the three diastereomers were 0.1 ng/ mL. The linear range was obtained in the range of 1-100 ng/mL for the total amount of three HBCD diastereomers. It was satisfactory to analyze real environmental water samples with the recoveries ranging from 77.2% to 99.3%. The main advantage of the method is toxic organic solvent-free.

Principle and performance of multi-frequency and multi-GNSS PPP-RTK

PPP-RTK which takes full advantages of both Real-Time Kinematic(RTK)and Precise Point Positioning(PPP),is able to provide centimeter-level positioning accuracy with rapid integer Ambiguity Resolution(AR).In recent years,with the development of BeiDou Navigation Satellite System(BDS)and Galileo navigation satellite system(Galileo)as well as the modernization of Global Positioning System(GPS)and GLObal NAvigation Satellite System(GLONASS),more than 140 Global Navigation Satellite System(GNSS)satellites are available.Particularly,the new-generation GNSS satellites are capable of transmitting signals on three or more frequencies.Multi-GNSS and multi-frequency observations become available and can be used to enhance the performance of PPP-RTK.In this contribution,we develop a multi-GNSS and multi-frequency PPP-RTK model,which uses all the available GNSS observations,and comprehensively evaluate its performance in urban environments from the perspectives of positioning accuracy,convergence and fxing percentage.In this method,the precise atmospheric corrections are derived from the multi-frequency and multi-GNSS observations of a regional network,and then disseminated to users to achieve PPP rapid AR.Furthermore,a cascade ambiguity fxing strategy using Extra‐Wide‐Lane(EWL),Wide-Lane(WL)and L1 ambiguities is employed to improve the performance of ambiguity fxing in the urban environments.Vehicle experiments in diferent scenarios such as suburbs,overpasses,and tunnels are conducted to validate the proposed method.In suburbs,an accuracy of within 2 cm in the horizontal direction and 4 cm in the vertical direction,with the fxing percentage of 93.7%can be achieved.Compared to the GPS-only solution,the positioning accuracy is improved by 87.6%.In urban environments where signals are interrupted frequently,a fast ambiguity re-fxing can be achieved within 5 s.Moreover,multifrequency GNSS signals can further improve the positioning performance of PPP-RTK,particularly in the case of small amount of observations.These results demonstrate that the multi-frequency and multi-GNSS PPP-RTK is a promising tool for supporting precise vehicle navigation.

PPP-RTK considering the ionosphere uncertainty with cross-validation

With the high-precision products of satellite orbit and clock,uncalibrated phase delay,and the atmosphere delay corrections,Precise Point Positioning(PPP)based on a Real-Time Kinematic(RTK)network is possible to rapidly achieve centimeter-level positioning accuracy.In the ionosphere-weighted PPP–RTK model,not only the a priori value of ionosphere but also its precision afect the convergence and accuracy of positioning.This study proposes a method to determine the precision of the interpolated slant ionospheric delay by cross-validation.The new method takes the high temporal and spatial variation into consideration.A distance-dependent function is built to represent the stochastic model of the slant ionospheric delay derived from each reference station,and an error model is built for each reference station on a fve-minute piecewise basis.The user can interpolate ionospheric delay correction and the corresponding precision with an error function related to the distance and time of each reference station.With the European Reference Frame(EUREF)Permanent GNSS(Global Navigation Satellite Systems)network(EPN),and SONEL(Système d’Observation du Niveau des Eaux Littorales)GNSS stations covering most of Europe,the efectiveness of our wide-area ionosphere constraint method for PPP-RTK is validated,compared with the method with a fxed ionosphere precision threshold.It is shown that although the Root Mean Square(RMS)of the interpolated ionosphere error is within 5 cm in most of the areas,it exceeds 10 cm for some areas with sparse reference stations during some periods of time.The convergence time of the 90th percentile is 4.0 and 20.5 min for horizontal and vertical directions using Global Positioning System(GPS)kinematic solution,respectively,with the proposed method.This convergence is faster than those with the fxed ionosphere precision values of 1,8,and 30 cm.The improvement with respect to the latter three solutions ranges from 10 to 60%.After integrating the Galileo navigation satellite system(Galileo),the convergence time of the 90th percentile for combined kinematic solutions is 2.0 and 9.0 min,with an improvement of 50.0%and 56.1%for horizontal and vertical directions,respectively,compared with the GPS-only solution.The average convergence time of GPS PPP-RTK for horizontal and vertical directions are 2.0 and 5.0 min,and those of GPS+Galileo PPP-RTK are 1.4 and 3.0 min,respectively.