Quality prediction of air-cured cigar tobacco leaf using region-based neural networks combined with visible and near-infrared hyperspectral imaging.

Visible and Near-infrared hyperspectral imaging (VNIR-HSI) combined with machine learning has shown its effectiveness in various detection applications. Specifically, the quality of cigar tobacco leaves undergoes subtle changes due to environmental differences during the air-curing phase. This study aims to evaluate the feasibility of deep learning methods in overcoming data limitations to develop a VNIR-HSI prediction model for the quality of cigar tobacco leaves at different air-curing levels.

The synergetic effect of an aqua ligand and metal site on the performance of single-atom catalysts in HO synthesis: a density functional theory study.

Studying the effect of the coordination field on the catalytic property is critical for the rational design of outstanding electrocatalysts for HO synthesis. Herein, via density functional theory (DFT) calculations and ab initio molecular dynamic (AIMD) simulations, we built an effective computational framework to identify the synergetic effect of an aqua ligand and metal ion on the 2e ORR catalytic performance under gas condition and aqua solvent. Specifically, the screening results of 29 single-atom catalysts (SACs), TM@CN (TM = transition metal), indicated that Cu@CN features excellent catalytic property with thermal stability, lowest 2e ORR overpotential (0.

Dual effect of the coordination field and sulphuric acid on the properties of a single-atom catalyst in the electrosynthesis of HO.

Electrocatalytic synthesis of hydrogen peroxide (HO) the two-electron oxygen reduction reaction (2e ORR) is the ideal solution for on-site HO production. Herein, we propose a new strategy for creating new 2e ORR catalysts by introducing electron-deficient B atoms and electron-rich N atoms to regulate the coordination field of metal ions on a graphene substrate. Through the first-principles density functional theory (DFT) calculations, NiNB-h was screened out as it had a low overpotential (0.

Characteristic fragmentation behavior of tobacco-specific N-nitrosamines using electrospray ionization multistage tandem mass spectrometry incorporating deuterium labeling.

Rationale: Tobacco-specific N-nitrosamines (TSNAs) mainly include 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanabasine (NAB) and N-nitrosoanatabine (NAT) that are formed from tobacco alkaloids during the curing process and contained in tobacco and tobacco smoke. They are linked with carcinogenesis. Analytical methods for quality control of products and determination of their metabolites are therefore of great importance.

Quantitative determination of zidovudine diaryl phosphate triester pro-drugs in rat plasma by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry.

A rapid, simple, and sensitive high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) method was developed and validated for quantitative analysis of 3'-azido-3'-deoxythymidine (zidovudine, AZT) diaryl phosphate triester pro-drugs, in rat plasma using 2',3'-dideoxy-2'3'-didehydrothymidine (d4T) as internal standard (IS). The analytes were extracted from rat plasma with methanol after protein precipitation. The compounds were separated by HPLC with gradient elution (on a Shim-pack VP-ODS C(18) analytical column using a mobile phase of methanol/10mM ammonium acetate).

Negative ion electrospray ionization mass spectrometry of nucleoside phosphoramidate monoesters: elucidation of novel rearrangement mechanisms by multistage mass spectrometry incorporating in-source deuterium labelling.

Several O-2',3'-isopropylideneuridine-O-5'-phosphoramidate monoesters were synthesized and analyzed by negative ion electrospray ionization tandem mass spectrometry (ESI-MS(n)). Two kinds of novel rearrangement reactions were observed due to the difference in the amino acid in the nucleoside phosphoramidate monoesters, and possible mechanisms were proposed. One involves a five-membered cyclic transition state.