Mid-Infrared Variable Selection for Soil Organic Matter Fractions Based on Soil Model Systems and Permutation Importance Algorithm.

In this research, an attempt was made to classify soil samples according to the different fractions of soil organic matter (SOM) using model systems in which the ratio of the fractions of SOM is chemically mimicked. A mixture of starch and nicotinamide was used for the labile organic matter model, while a standard of humic acid was used for the stabile organic matter. Changing the threshold value in the selected ranges after a permutation importance algorithm is conducted using train models and test data set, a list of selected important wavelengths and their importance scores were obtained. Three regions for the classification of soil fractions within the estimated probability density function are most prominent: 800-1200 cm-1, 0.48-0.55; 1800-2000 cm-1, 0.52-0.62; and 2500-3200 cm-1, 0.48-0.62, where the first component represents the spectral range while the second component covers the range of the importance score. Obtained wavelength ranges indicate the importance of the aliphatic stretching and bending vibration region, as well as the total soil reflectance (mineral content) for the characterization of organic matter fractions. A comparative evaluation with literature data found that the obtained wavelengths have a potential for application in methods of proximal and remote detection/calibration of existing and development of new sensors for Advanced Spaceborne Thermal Emission and Reflection Radiometer satellites, specifically in the shortwave infrared and thermal infrared ranges.

DRIFT spectroscopic determination of clay and organic matter in sediment by mixed soil-sediment calibration approach.

Bioavailability and movement of pollutants through land and underground flows are strongly related to some of the sediment characteristics, such as clay minerals and organic matter. Therefore, the determination of clay and organic matter content in sediment is of great importance for environmental monitoring. Clay and organic matter in sediment were determined using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in combination with multivariate analysis methods. Sediment from different depths was used in combination with the soil samples of different texture. Using multivariate methods and DRIFT spectra, sediments from different depths were successfully grouped according to similarity to different texture soils. Also, a quantitative analysis of clay and organic matter content was performed, where a new calibration approach was used in which sediment samples combined with soil samples were used for principal component regression (PCR) calibration. PCR models for the assessment of clay and organic matter were determined for a total of 57 sediment samples and 32 soil samples, and satisfactory determination coefficients were obtained for linear models (0.7136 for clay and 0.7062 for organic matter). The obtained RPD values for both models gave very satisfactory values of 1.9 for clay, i.e., 1.8 for organic matter.

Mixed-monolayer functionalized gold nanoparticles for cancer treatment: Atomistic molecular dynamics simulations study.

Gold nanoparticles (AuNPs) are employed as drug carriers due to their inertness, non-toxicity, and ease of synthesis. An experimental search for the optimal AuNP design would require a systematic variation of physico-chemical properties which is time-consuming and expensive. Computational methods provide quicker and cheaper approach to complement experiments and provide useful guidelines. In this paper, we performed atomistic molecular dynamics simulations to study how the size, hydrophobicity, and concentration of the drug affect the structure of functionalized AuNPs in the aqueous environment. We simulated two groups of nano-systems functionalized with a zwitterionic background ligand, and a ligand carrying a drug (Quinolinol or Panobinostat). Results indicate that in the case of a hydrophobic drug (Quinolinol), the hydrophobicity drives the conformation changes of the coating layer. The tendency of the hydrophobic drug to reduce its solvent-accessible surface results in a decrease of the coating thickness and the overall NP size. Although the amount of accessible drug can be increased by increasing its initial concentration, it will compromise the solubility of the system. In the case of a hydrophilic drug (Panobinostat), the ligand in excess has a dominant influence on the final structure of the coating conformations. The percentage of accessible drug is significantly higher than in the hydrophobic systems for any given ratio. It implies that for hydrophilic systems we can generally expect higher biological efficiency. Our results highlight the importance of taking into account physico-chemical properties of drugs and ligands when developing gold-based nanosystems, especially in the case of hydrophobic drugs.

Investigation of chlorinated phenols sorption mechanisms on different layers of the Danube alluvial sediment.

The characteristics of the Danube river alluvial sediment are of great importance in assessing the risk for transport of pollutants to drinking water sources. Characterization of the sediment column layers has shown that the alluvial sediment, sampled near the city of Novi Sad, is a mesoporous sandy material with certain differences in the properties of individual layers. In order to investigate the sorption mechanisms of four chlorinated phenols (CPs) on the alluvial deposit, static sorption experiments were performed at pH 4, 7 and 10. The results of sorption experiments, confirmed by principal components analysis sugest different mechanisms govern the sorption process at different pH conditions. This can be attributed to the molecular characteristics of CPs, geosorbent properties and to variations in the surface charge of the sorbent at different pH conditions.

Spectroscopic monitoring of photocatalytic degradation of the insecticide acetamiprid and its degradation product 6-chloronicotinic acid on TiO2 catalyst.

Two spectroscopic methods, (1)H NMR and FTIR, were developed for the monitoring of the photocatalytic degradation of acetamiprid, a widely used pyridine-based neonicotinoid insecticide, in UV-irradiated aqueous suspensions of O(2)/TiO(2). The (1)H NMR method allowed also the identification of the intermediates such as 6-chloronicotinic and formic acids, as well as separate monitoring of the kinetics of degradation of acyclic and aromatic moieties based on the different chemical shifts of the protons belonging to the methyl group of the acyclic and selected proton of the heterocyclic aromatic moiety. The FTIR procedure enabled the monitoring of the kinetics of degradation of the cyano group of the compound. The obtained results are in good agreement with the comparative HPLC-DAD and HPLC-MS/MS measurements, which also enabled the identification of certain intermediates. To get a deeper insight into the complex photocatalytic process, the photocatalytic degradation of 6-chloronicotinic acid, a stable degradation intermediate of acetamiprid, was also investigated by (1)H NMR and HPLC-DAD methods. Based on the obtained data, a tentative reaction mechanism was proposed for the photocatalytic degradation of acetamiprid.