Impacts of Multiple Environmental Changes on Long- Term Nitrogen Loading From the Chesapeake Bay Watershed

Excessive nitrogen can enter estuarine and coastal areas from land, disturbing coastal ecosystems and causing serious environmental problems. The Chesapeake Bay is one of the regions that have experienced hypoxia and harmful algal blooms in recent decades. This study estimated nitrogen export from the Chesapeake Bay watershed (CBW) to the estuary from 1900 to 2015 by applying a state-of-the-art numerical model. Nitrogen loading from the CBW continually increased from the 1900s to the 1990s and has declined since then. The key contributors to nitrogen export have shifted from atmospheric nitrogen deposition (before the 1960s) to synthetic nitrogen fertilizer (after the 1980s). Antipollution policies and implementation measures have played critical roles in the decrease of nitrogen export since the 1980s, and further reduction in riverine nitrogen export will likely require regulation on the application of nitrogen fertilizer

Carbon Nanodots as Complexing Agent in the Formation of Lead(II) Sulfide Thin Films via Direct Deposition of Lead(II) Sulfide Powder

This study reveals for the first time the formation of lead(II) sulfide (PbS) thin films via direct deposition of PbS powder using carbon nanodots (Cdots) as a complexing agent. The chemical bath deposition (CBD) technique was utilized and the Cdots’ mass was varied, i.e., (in g) 3, 5, 7, and 9. The Cdots were prepared from the waste of a rice noodle production home industry via the low-temperature carbonization method. The Cdots were characterized using UV-Vis spectrophotometry, showing absorption peaks at 275 nm and 325 nm; PL, showing an emission peak at 500 nm with cyan luminescence; XRD, showing several peaks, indicating an incomplete carbonization process; FTIR, indicating the existence of C=C, C-H, C-O, and O-H functional groups; HRTEM, revealing the sizes of the Cdots in the range of 2 nm to 6 nm; and SEM, showing a smooth morphology of the Cdots’ surface. The thin films obtained were smooth with higher XRD peaks and better material distribution compared to pure PbS thin film. The band gap measurement indicated that the increase of the PbS band gap was caused by the increase of the Cdots’ mass. Hence, the thin films’ band gap may be tuned using the Cdots’ mass

Carbon Nanodots as Complexing Agent in the Formation of Lead(II) Sulfide Thin Films via Direct Deposition of Lead(II) Sulfide Powder

This study reveals for the first time the formation of lead(II) sulfide (PbS) thin films via direct deposition of PbS powder using carbon nanodots (Cdots) as a complexing agent. The chemical bath deposition (CBD) technique was utilized and the Cdots’ mass was varied, i.e., (in g) 3, 5, 7, and 9. The Cdots were prepared from the waste of a rice noodle production home industry via the low-temperature carbonization method. The Cdots were characterized using UV-Vis spectrophotometry, showing absorption peaks at 275 nm and 325 nm; PL, showing an emission peak at 500 nm with cyan luminescence; XRD, showing several peaks, indicating an incomplete carbonization process; FTIR, indicating the existence of C=C, C-H, C-O, and O-H functional groups; HRTEM, revealing the sizes of the Cdots in the range of 2 nm to 6 nm; and SEM, showing a smooth morphology of the Cdots’ surface. The thin films obtained were smooth with higher XRD peaks and better material distribution compared to pure PbS thin film. The band gap measurement indicated that the increase of the PbS band gap was caused by the increase of the Cdots’ mass. Hence, the thin films’ band gap may be tuned using the Cdots’ mass

Reactivity of Heteropolytungstate and Heteropolymolybdate Metal Transition Salts in the Synthesis of Dimethyl Carbonate from Methanol and CO2

A series of Keggin-type heteropoly compounds (HPC) having different countercations (Co, Fe) and different addenda atoms (W, Mo) were synthesized and characterized by means of Fourier-Transform Infrared Spectrometer (FT-IR) and X-ray powder diffraction (XRD). The catalytic properties of the prepared catalysts for the dimethyl carbonate (DMC) synthesis from CO2 and CH3OH were investigated. The experimental results showed that the catalytic activity is significantly influenced by the type of the countercation and addenda atoms transition metal. Among the catalysts examined, Co1.5PW12O40 is the most active for the DMC synthesis, owing to the synergetic effect between Co and W. Investigating the effect of the support showed that the least acidic one (Al2O3) enhanced the conversion but decreased the DMC selectivity in favor of that of methyl formate (MF), while that of dimethoxy methane remained stable

Prediction of the Nitrogen Content of Rice Leaf Using Multi-Spectral Images Based on Hybrid Radial Basis Function Neural Network and Partial Least-Squares Regression

This paper’s novel focus is predicting the leaf nitrogen content of rice during growing and maturing. A multispectral image processing-based prediction model of the Radial Basis Function Neural Network (RBFNN) model was proposed. Moreover, this paper depicted three primary points as the following: First, collect images of rice leaves (RL) from a controlled condition experimental laboratory and new shoot leaves in different stages in the visible light spectrum, and apply digital image processing technology to extract the color characteristics of RL and the morphological characteristics of the new shoot leaves. Secondly, the RBFNN model, the General Regression Model (GRL), and the General Regression Method (GRM) model were constructed based on the extracted image feature parameters and the nitrogen content of rice leaves. Third, the RBFNN is optimized by and Partial Least-Squares Regression (RBFNN-PLSR) model. Finally, the validation results show that the nitrogen content prediction models at growing and mature stages that the mean absolute error (MAE), the Mean Absolute Percentage Error (MAPE), and the Root Mean Square Error (RMSE) of the RFBNN model during the rice-growing stage and the mature stage are 0.6418 (%), 0.5399 (%), 0.0652 (%), and 0.3540 (%), 0.1566 (%), 0.0214 (%) respectively, the predicted value of the model fits well with the actual value. Finally, the model may be used to give the best foundation for achieving exact fertilization control by continuously monitoring the nitrogen nutrition status of rice. In addition, at the growing stage, the RBFNN model shows better results compared to both GRL and GRM, in which MAE is reduced by 0.2233% and 0.2785%, respectively

Uncovering LED light effects on plant growth: new angles and perspectives - LED light for improving plant growth, nutrition and energy-use efficiency

Light supplementation can increase crop yield in greenhouses by promoting photosynthesis and plant growth. However, the high energy costs associated with light supplementation are a predominant factor that limits development and profit improvement of controlled environment agriculture. Light-emitting diodes (LEDs) are a promising technology that has tremendous potential to improve irradiance efficiency and to replace traditionally used horticultural lighting. Compared with traditional light sources (e.g., high-pressure sodium lamps and metal halide lamps) used in crop production, LEDs have distinct advantages, such as their small size, long lifetime and high photoelectric conversion efficiency. Most importantly, as a monochromatic light source, the spectrum of LEDs can be adjusted based on plant growth requirements. This project aimed to investigate energy-use efficiency, vegetable nutrition and photosynthesis improvement of light supplementation in a protected horticulture system. In the initial phase, the effects of LED light on plant growth and light-use efficiency for pak choi and photosynthetic performance were investigated. The results showed that the highest fresh and dry weight and leaf area were observed under red and blue LED light, with the blue light percentage at 23%. Compared with fluorescent lamps (FL) with photosynthetic photon flux density (PPFD) at 220 μmol m-2 s-1, the light-use efficiency increased by 55, 114 and 115% for mixed red and blue LEDs with PPFD at 100, 150 and 220 μmol m-2 s-1, respectively. Monochromatic red- and blue-light LEDs resulted in significant decreases in Pn of tomato plants, but the stomatal conductance (Gs) for monochromatic blue LEDs was higher than that for FL. The effect of light spectrum composition on lettuce nutrition quality was also studied. Continuous light with combined red, green and blue LEDs exhibited a remarkable decrease in nitrate. Moreover, continuous LED light for 24 h significantly increased phenolic compound content and free-radical scavenging capacity in lettuce leaf

Evaluation of alternative solvents in common amide coupling reactions : replacement of dichloromethane and N,N-dimethylformamide

A range of alternative solvents have been evaluated within amidation reactions employing common coupling reagents with a view to identifying suitable replacements for dichloromethane and N,N-dimethylformamid