Chemometric Analysis of a Ternary Mixture of Caffeine, Quinic Acid, and Nicotinic Acid by Terahertz Spectroscopy

Caffeine, quinic acid, and nicotinic acid are among the significant chemical determinants of coffee quality. This study develops a chemometric model to quantify these compounds in ternary mixtures analyzed by terahertz time-domain spectroscopy (THz-TDS). A data set of 480 THz spectra was obtained from 80 samples. Combinations of data preprocessing methods, including normalization (Z-score, min-max scaling, Mie baseline removal) and dimensionality reduction (principal component analysis (PCA), factor analysis (FA), independent component analysis (ICA), locally linear embedding (LLE), non-negative matrix factorization (NMF), isomap), and prediction models (partial least-squares regression (PLSR), support vector regression (SVR), multilayer perceptron (MLP), convolutional neural network (CNN), gradient boosting) were analyzed for their prediction performance (totaling to 4,711,685 combinations). Results show that the highest quantification performance was achieved at a root-mean-square error of prediction (RMSEP) of 0.0254 (dimensionless mass ratio), using min-max scaling and factor analysis for data preprocessing and multilayer perceptron for prediction. Effects of preprocessing, comparison of prediction models, and linearity of data are discussed

Uniform electron gases

We show that the traditional concept of the uniform electron gas (UEG) --- a homogeneous system of finite density, consisting of an infinite number of electrons in an infinite volume --- is inadequate to model the UEGs that arise in finite systems. We argue that, in general, a UEG is characterized by at least two parameters, \textit{viz.} the usual one-electron density parameter $\rho$ and a new two-electron parameter $\eta$. We outline a systematic strategy to determine a new density functional $E(\rho,\eta)$ across the spectrum of possible $\rho$ and $\eta$ values.Comment: 8 pages, 2 figures, 5 table

Rotamers of halogenated CNPOS

This article presents theoretical data on geometric and energetic features of halogenated rotamers of the following backbone structures, C-C, N-N, P-P, O-O, S-S, N-P, O-S, C-N, C-P, C-O, C-S, N-O, N-S, P-O and P-S. The data is considered to be comprehensive combinations of non-metal elements in the form abcx-ydef whereby a,b,c,d,e,f are halogen (fluorine to iodine), hydrogen or a lone pair and x,y are carbon, nitrogen, phosphorus, oxygen and sulfur

Data for: Reinterpreting Popular Demonstrations for Use in a Laboratory Safety Session That Engages Students in Observation, Prediction, Recordkeeping, and Problem Solving

• VDOs and photos of eleven demonstration activities for an introductory undergraduate chemistry safety session are in folders A-K. The first two activities are a safety video and a lab tour. All other activities are drawn from popular demonstrations and presented in the context of chemical safety. These include bursting a balloon by toluene, creating dry ice fog in fume hood, a reaction forming a carbon snake, a glycerol and potassium permanganate reaction, creating a fireproof banknote, putting out a candle by a copper coil, putting out a candle by a test tube, demonstrating a can crushed by air pressure, and making a soda geyser. • Notes for instructors (Table 1S detailed procedures and Table 2S mapping to RAMP) • A safety poster for undergraduate teaching chemical laboratory • Survey items and results (+/-/∆ and CLASS for Figure 1

Data for: In silico geometric and energetic data of all possible simple rotamers made of non-metal elements

Geometric and energetic features of halogenated rotamers of the following backbone structures, C-C, N-N, P-P, O-O, S-S, N-P, O-S, C-N, C-P, C-O, C-S, N-O, N-S, P-O and P-S from quantum chemical calculations are presented. The data set is considered to be comprehensive combinations of non-metal elements in the form abcx-ydef whereby a,b,c,d,e,f are halogen (fluorine to iodine), hydrogen or a lone pair and x,y are carbon, nitrogen, phosphorus, oxygen and sulfur. Preliminary work on all possible halogenation of methane, ammonia, phosphine, water and hydrogen sulfide are also included

Data for: Reinterpreting Popular Demonstrations for Use in a Laboratory Safety Session That Engages Students in Observation, Prediction, Recordkeeping, and Problem Solving

• VDOs and photos of eleven demonstration activities for an introductory undergraduate chemistry safety session are in folders A-K. The first two activities are a safety video and a lab tour. All other activities are drawn from popular demonstrations and presented in the context of chemical safety. These include bursting a balloon by toluene, creating dry ice fog in fume hood, a reaction forming a carbon snake, a glycerol and potassium permanganate reaction, creating a fireproof banknote, putting out a candle by a copper coil, putting out a candle by a test tube, demonstrating a can crushed by air pressure, and making a soda geyser.• A safety poster for undergraduate teaching chemical laboratory Play list is available at https://www.youtube.com/playlist?list=PLNbV5znV1KFuIq4FHeB5rHrf-c48_9U_

Data for: Reinterpreting Popular Demonstrations for Use in a Laboratory Safety Session That Engages Students in Observation, Prediction, Recordkeeping, and Problem Solving

This is supplementary information for paper published in the Journal of Chemical Education.J. Chem. Educ. 2021, 98, 1, 191–197 https://doi.org/10.1021/acs.jchemed.9b00474• Videos and photos of eleven demonstration activities for an introductory undergraduate chemistry safety session are in folders A-K. The first two activities are a safety video and a lab tour. All other activities are drawn from popular demonstrations and presented in the context of chemical safety. These include bursting a balloon by toluene, creating dry ice fog in fume hood, a reaction forming a carbon snake, a glycerol and potassium permanganate reaction, creating a fireproof banknote, putting out a candle by a copper coil, putting out a candle by a test tube, demonstrating a can crushed by air pressure, and making a soda geyser.• A safety poster for undergraduate teaching chemical laboratory Playlist is available at https://www.youtube.com/playlist?list=PLNbV5znV1KFuIq4FHeB5rHrf-c48_9U_ZTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Data for: In silico geometric and energetic data of all possible simple rotamers made of non-metal elements

Geometric and energetic features of halogenated rotamers of the following backbone structures, C-C, N-N, P-P, O-O, S-S, N-P, O-S, C-N, C-P, C-O, C-S, N-O, N-S, P-O and P-S from quantum chemical calculations are presented. The data set is considered to be comprehensive combinations of non-metal elements in the form abcx-ydef whereby a,b,c,d,e,f are halogen (fluorine to iodine), hydrogen or a lone pair and x,y are carbon, nitrogen, phosphorus, oxygen and sulfur. Preliminary work on all possible halogenation of methane, ammonia, phosphine, water and hydrogen sulfide are also included

Data for: In silico geometric and energetic data of all possible simple rotamers made of non-metal elements

Geometric and energetic features of halogenated rotamers of the following backbone structures, C-C, N-N, P-P, O-O, S-S, N-P, O-S, C-N, C-P, C-O, C-S, N-O, N-S, P-O and P-S from quantum chemical calculations are presented. The data set is considered to be comprehensive combinations of non-metal elements in the form abcx-ydef whereby a,b,c,d,e,f are halogen (fluorine to iodine), hydrogen or a lone pair and x,y are carbon, nitrogen, phosphorus, oxygen and sulfur. Preliminary work on all possible halogenation of methane, ammonia, phosphine, water and hydrogen sulfide are also included