Estimation of the Yield and Plant Height of Winter Wheat Using UAV-Based Hyperspectral Images.

Crop yield is related to national food security and economic performance, and it is therefore important to estimate this parameter quickly and accurately. In this work, we estimate the yield of winter wheat using the spectral indices (SIs), ground-measured plant height (H), and the plant height extracted from UAV-based hyperspectral images (HCSM) using three regression techniques, namely partial least squares regression (PLSR), an artificial neural network (ANN), and Random Forest (RF). The SIs, H, and HCSM were used as input values, and then the PLSR, ANN, and RF were trained using regression techniques. The three different regression techniques were used for modeling and verification to test the stability of the yield estimation. The results showed that: (1) HCSM is strongly correlated with H (R2 = 0.97); (2) of the regression techniques, the best yield prediction was obtained using PLSR, followed closely by ANN, while RF had the worst prediction performance; and (3) the best prediction results were obtained using PLSR and training using a combination of the SIs and HCSM as inputs (R2 = 0.77, RMSE = 648.90 kg/ha, NRMSE = 10.63%). Therefore, it can be concluded that PLSR allows the accurate estimation of crop yield from hyperspectral remote sensing data, and the combination of the SIs and HCSM allows the most accurate yield estimation. The results of this study indicate that the crop plant height extracted from UAV-based hyperspectral measurements can improve yield estimation, and that the comparative analysis of PLSR, ANN, and RF regression techniques can provide a reference for agricultural management.

Estimation of Crop Growth Parameters Using UAV-Based Hyperspectral Remote Sensing Data.

Above-ground biomass (AGB) and the leaf area index (LAI) are important indicators for the assessment of crop growth, and are therefore important for agricultural management. Although improvements have been made in the monitoring of crop growth parameters using ground- and satellite-based sensors, the application of these technologies is limited by imaging difficulties, complex data processing, and low spatial resolution. Therefore, this study evaluated the use of hyperspectral indices, red-edge parameters, and their combination to estimate and map the distributions of AGB and LAI for various growth stages of winter wheat. A hyperspectral sensor mounted on an unmanned aerial vehicle was used to obtain vegetation indices and red-edge parameters, and stepwise regression (SWR) and partial least squares regression (PLSR) methods were used to accurately estimate the AGB and LAI based on these vegetation indices, red-edge parameters, and their combination. The results show that: (i) most of the studied vegetation indices and red-edge parameters are significantly highly correlated with AGB and LAI; (ii) overall, the correlations between vegetation indices and AGB and LAI, respectively, are stronger than those between red-edge parameters and AGB and LAI, respectively; (iii) Compared with the estimations using only vegetation indices or red-edge parameters, the estimation of AGB and LAI using a combination of vegetation indices and red-edge parameters is more accurate; and (iv) The estimations of AGB and LAI obtained using the PLSR method are superior to those obtained using the SWR method. Therefore, combining vegetation indices with red-edge parameters and using the PLSR method can improve the estimation of AGB and LAI.

Insight into the mechanism for the methanol synthesis via the hydrogenation of CO2 over a Co-modified Cu(100) surface: A DFT study.

A comprehensive density functional theory calculation was employed to investigate the reaction mechanism of methanol synthesis on a Co-modified Cu(100) surface via CO2 hydrogenation. The Cu(100) surface with embedded small Co clusters prepared experimentally was employed as a model system to explore the effects of Co dopant on the catalytic performance of Cu(100) surface towards CH3OH synthesis. The activation energy barriers and the reaction energies of 16 elementary surface reactions were determined. Our calculated results show that the most favorable reaction pathway for the hydrogenation of CO2 to CH3OH follows the sequence of CO2 → HCOO* →H2COO* →H2COOH* →H2CO* →H3CO* →H3COH*, and the OH* group hydrogenation to H2 O* is the rate-limiting step with an activation barrier of 112.3 kJ/mol. It is noted that, since the strength of Co-O bond is stronger than that of Cu-O bond, the introducing of Co dopant on the Cu surface can facilitate the formation of key intermediates for the CH3OH synthesis. Especially, the stability of the unstable dioxomethylene intermediate (H2COO*) found on the pure Cu(100) surface can be obviously enhanced on the Co-doped Cu(100) surface. As a result, with respect to the undoped surface, the productivity and selectivity towards CH3OH production on the Cu(100) surface will be improved after dispersing small Co clusters on the surface.

[Study of the Detection of Histidine Based on "On-Off" Fluorescence Probe of Carbon Dots].

An new type of switch "On-Off" fluorescence probe was constructed based on fluorescence carbon dots as a novel strategy to analyze trace histidine(His) which was proposed for the first time. In water solution with pH 7.6, the fluorescence of CDs was quenched with Ru3+ due to the formation of ground state compound through electrostatic attraction, and the system was thus "turned-off". The fluorescence intensity of CDs was "turned-on" due to the competition between His and Ru towards the surface of CDs. The effect of critical parameters including pH, buffer solutions, reaction temperature and time needed to grow the fluorescence intensity of CDs was studied. Results show thatin water solution with pH 7.6, and when the temperature was between 20~25 ℃, the fluorescence intensity of the released CDs displayed a linear relationship in the range of (6.5~219.3)×10-6 mol·L-1 of captopril. Lower limit of detection for His, at the signal-to-noise ratio of 3/(3δ), was 2.15×10-6 mol·L-1. The methodology was successfully applied for the determination of His in Compound Amino Acid Injections, with the RSD≤2.07%, and the recovery rate was between 95.7%～102.4%. The result of the experiment was satisfactory. On the one hand, the excellent optical character CDs was acted as "On-Off" fluorescence probe, which could be extent the application of CDs, on the other hand, the excellent performance of the proposed fluorescence probe shows that this method possesses the potential for practical application.

Dynamic-tuning yeast storage carbohydrate improves the production of acetyl-CoA-derived chemicals.

Acetyl-coenzyme A (Acetyl-CoA) and malonyl-coenzyme A (malonyl-CoA) are important precursors for producing various chemicals, and their availability affects the production of their downstream chemicals. Storage carbohydrates are considered important carbon and energy reservoirs. Herein, we find that regulating the storage carbohydrate synthesis improves metabolic fluxes toward malonyl-CoA. Interestingly, not only directly decreasing storage carbohydrate accumulation improved malonyl-CoA availability but also increasing the storage carbohydrate by UGP1 overexpression enables an even higher production of acetyl-CoA- and malonyl-CoA-derived chemicals. We find that Ugp1p overexpression dynamically regulates the carbon flux to storage carbohydrate synthesis. In early exponential phases, Ugp1 overexpression causes more storage carbohydrate accumulation, while the carbon flux is then redirected toward acetyl-CoA and malonyl-CoA in later phases, thereby contributing to the synthesis of their derived products. Our study demonstrates the importance of storage carbohydrates rearrangement for the availability of acetyl-CoA and malonyl-CoA and therefore will facilitate the synthesis of their derived chemicals.

Molecularly imprinted electrochemical luminescence sensor based on signal amplification for selective determination of trace gibberellin A3.

A new molecularly imprinted electrochemical luminescence (MIP-ECL) sensor was developed for Gibberellin A3 (GA3) determination. This sensor is based on competitive binding between the GA3 and the Rhodamine B (RhB)-labeled GA3 (RhB-GA3) to the MIP film. After the competitive binding, the residual RhB-GA3 on the MIP was electro-oxidized to produce RhB oxide, which could greatly amplify the weak electrochemiluminescence (ECL) signal of luminol. The ECL intensity decreased when the RhB-GA3 was replaced by GA3 molecules in the samples. Accordingly, GA3 was determined in the concentration range from 1 × 10(-11) to 3 × 10(-9) mol/L with a detection limit of 3.45 × 10(-12) mol/L. The sensor shows high sensitivity and selectivity, wide response range, good accuracy, and fast response. Beer samples were assayed by using the sensors, and the recoveries ranging from 96.0% to 103.2% were obtained.

Contemporary Research Progress on the Detection of Polycyclic Aromatic Hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are a class of the most common and widespread contaminants. The accumulation of PAHs has made a certain impact on the environment and is seriously threatening human health. Numerous general analytical methods suitable for PAHs were developed. With the development of economy, the environmental problems of PAHs in modern society are more extensive and prominent, and attract more attention from environmental scientists and analysts. Deeper understanding of the properties of PAHs depends on the advent of detection methods, which can also be more conducive to promoting the protection of the environment. Till now, more sensitive, more high-speed and more high-throughput analytical tools are being invented and have played important roles in the research of PAHs. In this short review article, we focused mainly on the contemporary analytical methods about PAHs. We started with a brief review on the hazards, migration, distribution and traditional analysis methods of PAHs in recent years, including liquid chromatography, gas chromatography, surface enhanced Raman spectroscopy and so on. We also presented the applications of the modern ambient mass spectrometry, especially microwave plasma torch mass spectrometry, in the detection of PAHs, as well as the far out novel results in our lab by using microwave plasma torch (MPT) mass spectrometry; for example, some new insights about Birch reduction, regular hydrogen addition and the robustness of molecular structure. These studies have demonstrated the versatility of MPT MS as a platform in the research of PAHs.

Biosensor-Coupled In Vivo Mutagenesis and Omics Analysis Reveals Reduced Lysine and Arginine Synthesis To Improve Malonyl-Coenzyme A Flux in Saccharomyces cerevisiae.

Malonyl-coenzyme A (malonyl-CoA) is an important precursor for producing various chemicals, but its low availability limits the synthesis of downstream products in Saccharomyces cerevisiae. Owing to the complexity of metabolism, evolutionary engineering is required for developing strains with improved malonyl-CoA synthesis. Here, using the biosensor we constructed previously, a growth-based screening system that links the availability of malonyl-CoA with cell growth is developed. Coupling this system with in vivo continuous mutagenesis enabled rapid generation of genome-scale mutation library and screening strains with improved malonyl-CoA availability. The mutant strains are analyzed by whole-genome sequencing and transcriptome analysis. The omics analysis revealed that the carbon flux rearrangement to storage carbohydrate and amino acids synthesis affected malonyl-CoA metabolism. Through reverse engineering, new processes especially reduced lysine and arginine synthesis were found to improve malonyl-CoA synthesis. Our study provides a valuable complementary tool to other high-throughput screening method for mutant strains with improved metabolite synthesis and improves our understanding of the metabolic regulation of malonyl-CoA synthesis. IMPORTANCE Malonyl-CoA is a key precursor for the production a variety of value-added chemicals. Although rational engineering has been performed to improve the synthesis of malonyl-CoA in S. cerevisiae, due to the complexity of the metabolism there is a need for evolving strains and analyzing new mechanism to improve malonyl-CoA flux. Here, we developed a growth-based screening system that linked the availability of malonyl-CoA with cell growth and manipulated DNA replication for rapid in vivo mutagenesis. The combination of growth-based screening with in vivo mutagenesis enabled quick evolution of strains with improved malonyl-CoA availability. The whole-genome sequencing, transcriptome analysis of the mutated strains, together with reverse engineering, demonstrated weakening carbon flux to lysine and arginine synthesis and storage carbohydrate can contribute to malonyl-CoA synthesis. Our work provides a guideline in simultaneous strain screening and continuous evolution for improved metabolic intermediates and identified new targets for improving malonyl-CoA downstream product synthesis.

Fluorescence imaging of Cys in keratinocytes upon UVB exposure using phenyl doped graphitic carbon nitride Nanosheets-Au nanoparticles nanocomposite.

Ultraviolet B (UVB) irradiation induces the generation of reactive oxygen species (ROS) and causes damages to human skin. The depletion of glutathione (GSH) to scavenge ROS can protect skin cells from oxidative damage. However, little is known about the concentration level changes of cysteine (Cys), a precursor of GSH in skin cells after exposure to UVB irradiation. Herein, phenyl doped graphitic carbon nitride nanosheets-Au nanoparticles nanocomposite was prepared by in situ deposition of Au nanoparticles on the surface of phenyl doped graphitic carbon nitride nanosheets and showed a turn-on fluorescence response toward Cys over homocysteine, glutathione under physiological conditions. In the presence of Cys, remarkable enhancement of green fluorescence was observed. This nanocomposite was successfully applied for fluorescence imaging of Cys in human skin epidermal cells and monitoring the changes of Cys concentration level under the oxidative stress upon exposure to UVB irradiation in keratinocytes. It was found that the concentration of Cys was increased in the initial period after exposure to UVB irradiation and then gradually decreased to the normal level for the synthesis of GSH to defense the oxidative stress. Our result helps to understand the physiological function of Cys in human skin cells under UVB exposure.

[A new and sensitive resonance scattering spectral method for the determination of H2O2 using acridine red].

Under the conditions of pH 5. 0 HAc-NaAc, 1. 6 X 10(-3) mol x L(-1) KI-8. 0 X 10(-5) mol x L(-1) Fe2+-4. 0X 10(-6) mol x L(-1) H2O2-40 microg x mL(-1) acridine red (AR), when there is H2O2, reacts with I- to form I3- . The acridine red reacts with I3- to form AR-I3 ion association molecule. Under the action of the intermolecular and hydrophobic forces, these association molecules automatically aggregate to form (AR-I3 ), association particles that exhibit three resonance scattering peaks at 320, 400 and 595 nm respectively. The H2O2 concentration in the range of 0. 50-16. OX 10(-6) mol x L(-1) is proportional to the resonance scattering at 400 nm. And a new resonance scattering spectral method was described for the determination of H2O2 in water samples with satisfactory results.

Carbon dots as fluorescent probe for "off-on" Detecting sodium dodecyl-benzenesulfonate in aqueous solution.

In this paper, we propose an "off-on" approach for the detection of sodium dodecyl-benzenesulfonate (SDBS) using carbon dots (CDs) as fluorescent probe. We firstly demonstrated that the fluorescence of CDs decreased apparently in the presence of ruthenium (Ru), and the system was thus "turn-off". The resulting CDs-Ru system was found to be sensitive to SDBS, SDBS not only serves to shelter the CDs effectively from being quenched, but also to reverse the quenching and restore the fluorescence due to its ability to remove Ru from the surface of CDs (turn-on). An eco-friendly, simple and sensitive platform for the detection of SDBS based on the CDs-Ru probes has been proposed. After the experimental conditions were optimized, the linear range for detection SDBS was 0.10-7.50 µg/mL, with correlation coefficient (r) 0.9988, detection limit was 0.033 µg/mL (3σ). This method is facile, rapid, low cost, environment-friendly, and possesses the potential for practical application.

A carbon dots-CdTe quantum dots fluorescence resonance energy transfer system for the analysis of ultra-trace chlortoluron in water.

In this paper, a fluorescence resonance energy transfer (FRET) system between fluorescence carbon dots (CDs, donor) and CdTe quantum dots (CdTe, acceptor) was constructed, and a novel platform for sensitive and selective determination of chlortoluron was accordingly proposed. It was found that in Tris-HCl buffer solution at pH=8.7, energy transfer from CDs to CdTe occurred, which resulted in a great enhancement of the fluorescence intensity of CdTe. Upon the addition of chlortoluron, in terms of strong interaction between chlortoluron and CdTe QDs through the formation of chlortoluron-CdTe ground state complex, resulted in CdTe fluorescence quenching. Under optimal conditions, in range of 2.4×10(-10)molL(-1)-8.5×10(-8)molL(-1), the change of CdTe fluorescence intensity was in good linear relationship with the chlortoluron concentration, and the detection limit was 7.8×10(-11)molL(-1) (S/N=3). Most of common relevant substance, cations and anions did not interfere with the detection of chlortoluron. The proposed method was applied to determine chlortoluron in water samples with satisfactory results.