Decades-long organic tea production is distinguished by N deficiency: Evidence from soil and tea δ15N data.

To investigate the possibility of identifying commercial organic teas from conventional teas based on their isotopic signatures, we sampled tea leaves and soil samples from three tea gardens in Pu'er, China, that underwent decades of certified organic cultivation and compared them with adjacent conventional gardens. We found that long-term organic tea cultivation increased the soil organic carbon and soil pH but significantly decreased the total N content of tea. Higher δ15N values were observed in the organic teas, but significant overlap existed with non-organic teas. The lower N content of the organic tea and contrasting pattern between the organic tea δ15N and soil δ15N suggested that the decline of the N availability could potentially act as a robust characteristic for discriminating between organic and non-organic tea cultivation systems. Further analysis implies that combining tea and soil N content with δ15N value is a promising approach to organic tea identification.

Seeking Tracking Consensus for General Linear Multiagent Systems With Fixed and Switching Signed Networks.

The existing studies for tracking consensus of multiagent systems (MASs) are all restricted to networks with only cooperative relationships among agents. Tracking consensus, however, requires beyond these traditional models due to the ubiquitous competition in many real-world MASs, such as biological systems and social systems. Taking into account this fact, this article aims to extend the dynamics of tracking consensus to signed networks containing both cooperative and competitive relationships among agents. A group of agents with general linear dynamics is considered. The cases of the fixed network as well as switching networks are analyzed, respectively. In the end, some algebraic conditions related to the network structure and the positive/negative edge weight are established to ensure the implementation of tracking consensus. Moreover, the single decoupling system is allowed to be strictly unstable in theory, and the upper bound of the eigenvalue modulus of the system matrix related to the system instability is given.

Asynchronous Tracking Control of Leader-Follower Multiagent Systems With Input Uncertainties Over Switching Signed Digraphs.

Signed digraphs with both positive and negative weighted edges are widely applied to explain cooperative and competitive interactions arising from various social, biological, and physical systems. This article formulates and solves the asynchronous tracking control problem of multiagent systems with input uncertainties on switching signed digraphs. In the interaction setting, we assume that the leader moves at a time-varying acceleration that cannot be measured by the followers accurately, and further suppose that each agent receives its neighbors' states information at certain instants determined by its own clock, which is not necessary to be synchronized with those of other agents. Using dynamically changing spanning subdigraphs of signed digraphs to describe graphically asynchronous interactions, the asynchronous tracking problem is equivalently transformed into a convergence problem of products of general substochastic matrices (PGSSM), in which the matrix elements are not necessarily non-negative and the row sums are less than or equal to 1. With the help of the matrix analysis technique and the composition of binary relations, we propose a new and original method to deal with the convergence problem of PGSSM, and further establish a spanning tree condition for asynchronous tracking control. Finally, the validity of the theoretical findings is verified through several numerical examples.

Comprehensive investigations revealed consistent pathophysiological alterations after vaccination with COVID-19 vaccines.

Large-scale COVID-19 vaccinations are currently underway in many countries in response to the COVID-19 pandemic. Here, we report, besides generation of neutralizing antibodies, consistent alterations in hemoglobin A1c, serum sodium and potassium levels, coagulation profiles, and renal functions in healthy volunteers after vaccination with an inactivated SARS-CoV-2 vaccine. Similar changes had also been reported in COVID-19 patients, suggesting that vaccination mimicked an infection. Single-cell mRNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) before and 28 days after the first inoculation also revealed consistent alterations in gene expression of many different immune cell types. Reduction of CD8+ T cells and increase in classic monocyte contents were exemplary. Moreover, scRNA-seq revealed increased NF-κB signaling and reduced type I interferon responses, which were confirmed by biological assays and also had been reported to occur after SARS-CoV-2 infection with aggravating symptoms. Altogether, our study recommends additional caution when vaccinating people with pre-existing clinical conditions, including diabetes, electrolyte imbalances, renal dysfunction, and coagulation disorders.

Bipartite Tracking Consensus of Generic Linear Agents With Discrete-Time Dynamics Over Cooperation-Competition Networks.

This article addresses the bipartite tracking consensus for a set of mobile autonomous agents over directed cooperation-competition networks. Here, cooperative and competitive interactions among the agents are described by positive and negative edges of the directed network topology, respectively. Both fixed and switching network topologies are considered. For the case with fixed network topology, the matrix product technique is utilized to derive the convergence result. For the case with switching network topologies, some key results related to the composition of binary relations are the main technical tools of analyzing the error system. In addition, the upper bound for the spectral radius of the system matrix is given to ensure the convergence of the system even if the single uncoupled system is strictly unstable. The applicability of the derived results is verified through two simulation experiments.

An Analysis on Optimal Attack Schedule Based on Channel Hopping Scheme in Cyber-Physical Systems.

In this paper, we investigate the issue of security on the remote state estimation in cyber-physical systems (CPSs), where a wireless sensor utilizes the channel hopping scheme to transmit the data to the remote estimator over multiple channels in the presence of periodic denial-of-service attacks. Assume that the jammer can interfere with a subset of channels at each attack time in active period. For an energy-constraint jammer, the problem of how to select the number of channels at each attack time to maximally deteriorate the CPS performance is investigated. Based on the index of average estimation error, we introduce two different attack strategies, which include selecting identical number of channels and unequal number of channels at each attack time, and further show theoretically that the attack effect by selecting unequal number of channels is better than that of selecting identical number of channels. By formulating the problem of selecting the number of channels as integer programming problems, we present the corresponding algorithm to approximate the optimal attack schedule for both cases. The numerical results are presented to validate the theoretical results and the effectiveness of the proposed algorithms.

The level variation of Nε-(carboxymethyl)lysine is correlated with chlorogenic acids in Arabica L. Coffee beans under different process conditions.

Nε-(carboxymethyl) lysine (CML) is universally used as a marker of the occurrence of advanced glycation end products (AGEs) in foods. This study investigated the level changes of CML, chlorogenic acids (CQAs), lysine (Lys), fat and pH in coffee during roasting. The CML level went up slowly in the first 10 mins, then declined sharply during the next 2 mins, and kept increasing constantly in the following baking time, while the lowest CML level was obtained by roasting at 235 °C for 12 mins. The three CQAs isomers had different efficacy in affecting the levels of CML and other factors, indicating the CQAs isomers may play an important role in influencing the CML level. So it might be possible to regulate the formation of CML and gain better coffee quality via adjusting the levels of CQAs in baking process. This study provided important enlightenment on CML control during coffee baking.

Containment Control of Asynchronous Discrete-Time General Linear Multiagent Systems With Arbitrary Network Topology.

In this contribution, we propose and investigate the containment control issue for general linear multiagent systems (MASs) under the asynchronous setting, where the network topology is not subjected to any structural restrictions and the roles of the leaders and the followers are entirely determined by the network topology. It is assumed that the interaction time instants of each agent, at which this agent interacts with its neighbors, are independent of the other agents' and can be unevenly distributed. An asynchronous distributed algorithm is proposed to implement the control strategy of linear MASs. The non-negative matrix theory and the composition of binary relations are utilized to handle the asynchronous containment control issue. It is shown that the leaders in each closed and strongly connected component of the network topology will reach a common state and the followers will gradually enter the dynamic convex hull constructed by the leaders. Moreover, it is also proved that the system matrix can be strictly unstable, and the upper bound of the system matrix's spectral radius is explicitly stated. Finally, two simulation examples are also provided to verify the efficacy of our theoretical results.

[Determination of bisultap residue in tropical fruits by ultra performance liquid chromatography-tandem mass spectrometry].

A method for the determination of bisultap in tropical fruits was developed by modified QuEChERS method and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The tropical fruit samples were twice extracted with acetonitrile containing 1% (v/v) acetic acid, and purified by 200 mg of primary secondary amine (PSA), 100 mg of C18, 300 mg of MgSO4 and 500 mg of disodium hydrogen citrate. The analyte was separated on a CAPCELL CORE PC hydrophilic column, detected in the negative ion multiple reaction monitoring (MRM) mode, and quantified by external standard method. A good linear relationship in the range of 0.1-10.0 µg/L was obtained with the correlation coefficient (r2) of 0.9993. The limit of detection and limit of quantification were 0.015 µg/kg and 0.05 µg/kg, respectively. The spiked recoveries were in the range of 81.0%-88.3% with the relative standard deviations from 3.9% to 6.2%. The method has good purification effect and high sensitivity, and is suitable for the rapid analysis of the bisultap residues in tropical fruits.

Event-triggered containment control for second-order multi-agent systems with sampled position data.

This paper is concerned with the problem of event-triggered containment control for second-order multi-agent systems with sampled position data. First, a distributed event-triggered containment control protocol is designed, which utilizes the sampled position data only and allows the event-triggering condition to be intermittently examined at constant sampling instants. Then, based on the algebraic graph theory and matrix theory, a sufficient condition on the communication topology, the controller gains, and the sampling period is derived so as to achieve containment control. Finally, a numerical example is provided to verify the theoretical results.

[Determination of 41 pesticide residues in vegetables by QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry].

A multiresidue analytical method for the rapid determination of 41 pesticide residues in vegetables was developed by using QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), including recessive pesticides, banned pesticides and pesticides with restrict use, plant growth regulators and some other pesticides with high detection rates. The vegetable sample was extracted by 1% (v/v) acetic acid-acetonitrile, cleaned-up by primary secondary amine (PSA) and injected for analysis. The positive and negative ion modes and multiple reaction monitoring (MRM) mode were used in the analysis, and the analytes were quantified by the external standard method. Under the conditions of optimized QuEChERS, chromatography and mass spectrometry, the 41 pesticides showed good linearities in the range of 1.0 µg/L to 100 µg/L, with the correlation coefficients (r2) higher than 0.999. The limits of detection of the method were 0.003 µg/kg to 1.00 µg/kg. The average recoveries of the 41 pesticides in different matrices were in the range of 74.1%-120.4% with the relative standard deviations from 2.8% to 11.9%. The method has the advantages of rapidity, simplici- ty, high sensitivity and better purification effect. It is suitable for the rapid determination of the common pesticides in vegetables, and it provides a strong guarantee for the risk assessment of the quality and safety of vegetables.

[Determination of nine estrogenic steroids in milk using matrix solid phase dispersion-ultra performance liquid chromatography with mass spectrometric detector].

An analytical method for the multiresidue determination of nine estrogenic steroids in milk was developed by modified matrix solid phase dispersion (MSPD) purification and ultra performance liquid chromatography (UPLC) with mass spectrometric detector (MSD). The sensitivity and accuracy of MSD were better than that of ultraviolet detector. In comparison with traditional mass spectrometry, the merits of MSD were simpler in operation and shorter in starting time (5 min). The results showed that the limits of detection of the compounds with nucleophilic substitution were high in positive ion mode of MSD and were easily affected by environmental conditions. The matrix effects of milk samples reduced from 84%-160% to 80%-121% after MSPD purification. The intraday precision and interday precision of the nine estrogenic steroids were 0.87%-1.78% and 1.82%-3.79%, respectively. The average recoveries were 68.7%-94.7%, and the relative standard deviations (RSDs) were less than 10%. The limits of detection (LODs) were 0.5-10 µg/kg. The limits of quantification (LOQ) were 2-20 µg/kg.

Determination of trigonelline, nicotinic acid, and caffeine in Yunnan Arabica coffee by microwave-assisted extraction and HPLC with two columns in series.

A simple, rapid method was developed for simultaneous extraction of trigonelline, nicotinic acid, and caffeine from coffee, and separation by two chromatographic columns in series. The trigonelline, nicotinic acid, and caffeine were extracted with microwave-assisted extraction (MAE). The optimal conditions selected were 3 min, 200 psi, and 120 degrees C. The chromatographic separation was performed with two columns in series, polyaromatic hydrocarbon C18 (250 x 4.6 mm id, 5 microm particle size) and Bondapak NH2 (300 x 3.9 mm id, 5 microm particle size). Isocratic elution was with 0.02 M phosphoric acid-methanol (70 + 30, v/v) mobile phase at a flow rate of 0.8 mL/min. Good recoveries and RSD values were found for all analytes in the matrix. The LOD of the three compounds was 0.02 mg/L, and the LOQ was 0.005% in the matrix. The concentrations of trigonelline, nicotinic acid, and caffeine in instant coffee, roasted coffee, and raw coffee (Yunnan Arabica coffee) were assessed by MAE and hot water extraction; the correlation coefficients between concentrations of the three compounds obtained were close to 1.

Fast separation ultra-performance liquid chromatography for determination of pre-column derivative abamectin and ivermectin residues in vegetable.

A new residue method for quantification of abamectin and ivermectin in vegetable is described in the article. The derivative process is devised that acylating chemical is firstly performed by N-methylimidazole (MI) and trifluoroacetic anhydride (TFAA), then which reacted with hydroxyl function of abamerctin to make fluorescence. The influence of triethylamin (TEA) is examined. Separation is resolute by a short column of 1.7 µm size and operated at high pressure values (10.000 psi). The optimal chromatographic condition and the highest sensitivity are achieved by acetonitrile: water (95: 5), 0.4 mL/min, 0.2 µL injector. The detection limits of abamectin and ivermectin are 1 µg/kg respectively.

[Determination of trigonelline in coffee powder and instant coffee by ultrasonic extraction and high performance liquid chromatography].

A method of high performance liquid chromatography was established for the analysis of trigonelline in coffee powder and instant coffee. The separation was performed on a BondPak NH2 column (250 mm x 4.6 mm, 5 microm). The mobile phase was methanol-water (82: 18, v/v) at a flow rate of 0.8 mL/min. The detection wavelength was set at 260 nm. The method had good linearity in the range of 1 - 40 mg/L (the correlation coefficient was 0.9998). The repeatability of the method was performed at one day, different days, and by two analysts. The accuracy of the method was evaluated by recovery study. The recoveries were more than 90% with the relative standard deviations less than 3%. The contents of trigonelline in samples were assessed with ultrasonic extraction and hot water extraction, separately, and the regression coefficient between trigonelline contents obtained under the two extraction methods was 0.9964. The method is simple, rapid, highly sensitive, and suitable for the analysis of trigonelline and quality control of coffee samples.