Infrared Spectroscopy Methods Research Articles

Determination of concentration of basic sites on oxides by IR spectroscopy

As it is commonly known, CO2 reacts simultaneously with basic O2− and basic OH sites on oxides forming carbonates and bicarbonates, which can be followed by infrared spectroscopy (IR). However, here, we succeeded to elaborate experimental conditions under which CO2 reacted solely with O2− forming CO32− for ZrO2 and CeO2, and calculated the extinction coefficients of diagnostic bands of carbonate and bicarbonate species. For the first time, the developed IR method enabled the concentrations of O2− and basic OH for ZrO2, CeO2, Al2O3 and CuO to be measured separately. Moreover, in the case of all IR studied oxides, the sum of concentrations of O−2 and basic OH basic sites was comparable with the concentration determined by pulse adsorption of CO2. Thus, the presented extinction coefficients can be applied for IR basicity studies of various basic catalysts. We also followed the effect of thermal treatment on basicity of oxides.

Microplastics removal efficiency and risk analysis of wastewater treatment plants in Oman

Microplastics (MPs) have recently been documented as an emerging pollutant that poses a critical threat to environment. Wastewater treatment plants (WWTPs) are commonly regarded as significant contributors to the presence of MPs. This study aimed to assess the MPs load of three wastewater treatment facilities in Oman using various treatments, including MBR, SBR, and CAS. Wastewater samples from influent, effluent, and sludge were collected and analyzed to determine the concentration, morphology, size, color, and polymer type of the MPs. A set of sieves with a mesh size range of 1 mm–45 μm was used to for filtration. Oxidation treatment was applied for all samples using Fenton's reagent, followed by density separation by sodium chloride solution. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR- FTIR) method was utilized to test 10% from each sampling point to confirm the polymer types of the MPs. The pollution load index (PLI) and hazard index (HI) have been employed to assess the risk associated with the chemical toxicity and concentration of detected particles. The PROMETHEE method was used to rank the risk of sampling sites based on different criteria that posed potential ecological and human health risks. The results indicate that the average concentrations of 0.99 MP/L, 1.38 MP/L, and 0.93 MP/L were detected in the final treated effluent of WWTP A, WWTP B, and WWTP C, respectively. These concentrations correspond to overall removal efficiencies of 82.5%, 77.4%, and 79.2% for WWTP A, WWTP B, and WWTP C, respectively Most MPs found in tertiary effluent were smaller particles (425 μm) and fiber-shaped. The major types of MPs were polypropylene (PP), low-density polyethylene (LDPE), polyurethane (PU), polyethylene terephthalate (PET), and Polyvinyl chloride (PVC). This study showed that treated effluent and sludge release significant MPs into the environment.

Variations of the fundamental chemical components in Moso bamboo (Phyllostachys pubescens)

ABSTRACT The utilization of bamboo as a substitute for wood or plastic signifies an imperative pathway towards achieving global sustainable development. The conduct of comprehensive and systematic research on the variations in the fundamental chemical compositions can offer scientific and theoretical guidance for the efficient and rational high-value utilization of bamboo. In this study, the variations of the content of primary chemical components in Moso bamboo (Phyllostachys pubescens) were systematically investigated by considering height and radial locations. This was achieved through using comprehensive chemical analysis and infrared spectroscopy methods, with an additional investigation into the impact of nodes on these variations. The results indicated that the fundamental chemical components of Moso bamboo consisted of cellulose, hemicelluloses and lignin. The cellulose content ranged from 36% to 40%, the hemicelluloses content ranged from 25% to 28%, and the lignin content ranged from 26% to 34%. The cellulose content decreased with increasing culm height, while it demonstrated a gradual increase during the transition from the inner to the outer layer of the wall. The cellulose content of the internodes was higher than that of the nodes. The variation in cellulose content was more pronounced in the radial direction compared to that in vertical direction. However, the hemicelluloses and lignin content in the bamboo culm showed no statistical differences. The abundant resource advantage of bamboo in China can provide a valuable resource benefit for the classification and utilization of its three fundamental chemical components. The findings derived can provide a reliable basis for establishing a scientific theoretical foundation to optimize the value-added utilization of bamboo.

Near infrared spectroscopy for determination of moisture content in lyophilized formulation

A non-invasive near infrared (NIR) spectroscopic method was developed for the quantitative moisture determination in a lyophilized injection formulation. The calibration samples were prepared by exposing lyophilized samples at different temperatures and relative humidity. The samples from different scales and different process parameters were considered for adding robustness to the model. The NIR spectra were collected using a Fourier-transform (FT) NIR with a diffuse reflectance probe and the same samples were further analyzed by the Karl Fisher (KF) method for moisture content. The pre-treated NIR spectra were used for quantitative method development for moisture content. Partial least squares regression was used to develop calibrations in the 5600-4950 cm−1 region with calibration coefficient of determination (R2) of 0.96 and root mean square error of calibration (RMSEC) of 0.149. The model was cross-validated internally using the Kernel algorithm with r2 = 0.96 and RMSECV = 0.15. The accuracy of the NIR method against the KF method, precision, and reproducibility were good and the model was robust in predicting different external validation samples. This work allowed NIR as an alternative measurement for moisture analysis as well as facilitate 100% monitoring before packaging and save the cost of sample and time of KF analysis.

An Evaluation of the Beneficial Effects of Polyamide 6's Thermal Stabilization by Ferric Chloride Complexation as a Novel Carbon Fiber Precursor

This study investigated the impact of stabilization time on pretreated polyamide 6 (PA6) fibers using various analytical techniques, including thermal analysis (TGA and DSC), infrared (IR) spectroscopy, X-ray diffraction (XRD), tensile testing, and density measurements. The two-step atmospheric air-based stabilization process for pretreated PA6 multifilament bundles involved initial thermal stabilization at 170 °C in an air atmosphere after ferric chloride impregnation, followed by a second step of thermal stabilization at 245 °C. Ferric chloride impregnation followed by thermal stabilization in an air atmosphere resulted in crucial structural transformations. The density values of the samples increased following thermal stabilization, accompanied by a decrease in tensile values. Ferric chloride pretreated and thermally stabilized PA6 fibers were found to be fully stabilized after 120 min of stabilization before the carbonization stage. The findings obtained from the DSC, XRD, and IR spectroscopy methods indicated the occurrence of disordering phases due to the scission of hydrogen bonds. The TGA findings showed significant increases in carbon yield percentages at 500 °C and 850 °C, reaching 71.4% and 63.5%, respectively, for the sample heat treated at 245 °C for 120 min. The addition of ferric chloride is expected to potentially reduce processing costs for final carbon fiber production by decreasing the time required for the thermal stabilization of PA6.

Cotton Fiber Strength Measurement and Its Relation to Structural Properties from Fourier Transform Infrared Spectroscopic Characterization

There has been an interest in understanding the relationship between textile cotton fiber strength (or tenacity) and structure for better fiber quality measurement and enhancement. This study utilized coupled Stelometer and high volume instrument (HVI) measurements with attenuated total reflection Fourier transform infrared spectroscopy methods to relate fiber strength and associated properties (Stelometer elongation and HVI micronaire) with structure properties on six Upland (as A, B, C, D, E, and F) and one Pima cultivar. Although Stelometer tenacity agreed with HVI strength in general, the Upland D cultivar (immature) was observed to show the lowest HVI strength value, while the Upland F cultivar (larger infrared crystallinity index) was found to possess the smallest Stelometer tenacity value. A few strong and significant correlations were noted, for example, between infrared crystallinity and Stelometer elongation for the Upland A fibers, between infrared maturity and Stelometer tenacity for the Upland C fibers, and between infrared maturity and HVI strength for the Upland D fibers. Furthermore, there were apparent distinctions in regressions and statistics of examined correlations between each Upland cultivar and their combined fiber set, addressing the challenge of understanding the unique response between fiber physical and structure properties from different measurements even within one cotton cultivar.

Re-engineering and regulating molecular architecture of synthetic capsaicin for enhanced water-based degradation performance

Synthetic capsaicin, also known as pelargonic acid vanillylamide (PAVA), constitutes the primary component in riot control agents. Due to the propensity of PAVA agglomerated in aqueous environments, the interaction between the active site of PAVA molecular and catalyst was restricted, consequently reducing its degradation efficiency in water-based oxidizing agents. This study used a cationic surfactant, dodecyl trimethyl ammonium chloride (DTAC), in combination with KOH for the precise regulation and arrangement of PAVA molecules, resulting in the formation of a distinctive hydrophilic structure. This approach resolved its poor solubility in aqueous solutions while the relationship between solubility and degradation rate was obtained. The frontier orbital distribution and surface electrostatic potential distribution of PAVA molecular were predicted through first-principles calculation. The mechanism of PAVA solubilization was studied by 1H NMR techniques and infrared spectroscopy methods. The results showed that KOH substitutes the phenolic hydroxyl group “–OH” of PAVA, forming potassium phenoxide “–OK”, which enhanced the solubility of PAVA in water. Additionally, KOH might reduced the surface tension in the solution. It promotes the formation of the DTAC/PAVA complex micelle structure, which exhibited the PAVA agglomerates to exposing the catalytic activation reaction sites and accelerating the catalytic oxidation.

Physical and chemical properties, hygienic quality and fatty acid profile in milk of lactating Lacaune dairy sheep

Abstract. In recent years, there has been globally increasing interest in dairy sheep breeding, including Lacaune sheep, which is supported by a high demand for sheep's milk on the market. This paper elaborates on the influence of a sheep's lactation stage on the physical and chemical properties, hygienic quality and content of fatty acids in milk produced by Lacaune sheep kept in intensive breeding. The research was conducted on 30 Lacaune sheep, which were tested in the early (60th day), middle (120th day) and late (180th day) stages of lactation. Density, freezing point and titration acidity were determined by applying the infrared spectrometry method, and indicators of the hygienic quality of milk, such as somatic cell count (SCC), were determined by the fluoro-opto-electronic method, and the total count of aerobic mesophilic bacteria (CFU) was determined by the flow cytometry method. The fatty acid profile of feed and milk was obtained by gas–liquid chromatography. Depending on the stage of lactation, results referring to the chemical composition of Lacaune sheep's milk showed a significant increase in the content of fat, protein, total dry matter and casein together with a significant decrease in the content of lactose in the late stage of lactation. There was also a significant increase confirmed for the concentration of urea and the freezing point in milk along with the lactation progress. Depending on the stage of lactation, milk yield in Lacaune sheep significantly decreased as lactation progressed. Analysis of the fatty acid composition in milk of Lacaune sheep proved a significant decrease in the concentrations of C4 : 0, C6 : 0, C11 : 0, C12 : 0, C13 : 0, C15 : 0, C17 : 1, C18 : 2n6 and C18 : 3n6 as well as the n6 concentrations and the n6 / n3 ratio. The opposite trend was observed for concentrations of C10 : 0, C14 : 1, C16 : 0, C16 : 1, C18 : 0, C20 : 2, C18 : 3n3, C20 : 3n6, C20 : 5n3 and C22 : 6n3 as well as for the n3 concentrations. When compared to the early lactation stage, the C18 : 3n6 and n6 concentrations were significantly lower in the late lactation stage, while the C20 : 2 and C20 : 5n3 concentrations were significantly lower in the middle lactation stage when compared to the late lactation stage. There were many significant positive and negative correlations determined between the researched properties of milk. The research results obtained with Lacaune sheep's milk can be compared to the results of other studies, except for the lower content of milk fat. This confirms the good adaptability of Lacaune sheep to different breeding conditions and the necessity to provide sheep with quality pastures for grazing.

Development and Validation of FT-IR Spectrophotometric Method for Simultaneous Estimation of Clonidine Hydrochloride and Chlorthalidone in Pharmaceutical Synthetic Mixture

A precise, simple, cost effective, accurate, eco-friendly and validated fourier transform infrared spectroscopy method has been developed for the simultaneous estimation of Clonidine Hydrochloride and Chlorthalidone in pharmaceutical synthetic mixture. The developed method involves measurement of spectral wavenumber of the infrared band corresponding to (–C=N) from 1658.78 cm-1 for Clonidine Hydrochloride and (-S=O) group from 1346.31 cm-1 for Chlorthalidone. Over the range of 1.5–3% w/w for Clonidine hydrochloride and 15–90% w/w for Chlorthalidone, the method was found to be linear. It has correlation coefficient (r2) of 0.999 for Clonidine hydrochloride and 0.994 for Chlorthalidone. According to ICH guidelines, in terms of accuracy, linearity, limit of detection and limit of quantitation, precision, the developed method was validated. In addition to this, degradation behaviours of Clonidine Hydrochloride and Chlorthalidone were studied by subjecting them to sunlight, photolytic and thermal degradation.

System "dispersed polyvinyl acetate-calcium silicate" in furnishing materials

This article focuses on the processes of interaction between calcium silicate hydrates and dispersed polyvinyl acetate in tight films with the aim of developing compounds meant for restoration and finishing works. The basis of this development relies on the concept concerning the determining role of the crystal-chemical factor of the silicate phase in the formation of organic-mineral compounds of increased durability. The characteristics of dispersed calcium silicate hydrates are portrayed. The preparation conditions, accounting for the synthesis of the product of submicrocrystalline structure, conforming with the stoichiometry CaO:SiO2=0.8-2.0 have been determined. The interaction has been studied for compounds achieved by mixing ingredients in a rapid whirling mixer, and subjected to hardening at T=20+2 °C. With the aid of XRD, DTA and Infra-Red Spectrometry methods the formation process of the sophisticated polymer silicate phase in the material was observed for a period of 90 days. The properties of the film were investigated and its high resistance against the influence of external factors was established. On this basis a conclusion concerning the quite high effectiveness of substituting portland cement with dispersed calcium silicate hydrate in polymer cement compounds has been made White colour and other various special properties determine the suitability for repair and finishing works on facades of buildings.

Analysis and comparison of machine learning methods for species identification utilizing ATR-FTIR spectroscopy

Accurate identification of insect species holds paramount significance in diverse fields as it facilitates a comprehensive understanding of their ecological habits, distribution range, and impact on both the environment and humans. While morphological characteristics have traditionally been employed for species identification, the utilization of empty pupariums for this purpose remains relatively limited. In this study, ATR-FTIR was employed to acquire spectral information from empty pupariums of five fly species, subjecting the data to spectral pre-processing to obtain average spectra for preliminary analysis. Subsequently, PCA and OPLS-DA were utilized for clustering and classification. Notably, two wavebands (3000–2800 cm−1 and 1800–1300 cm−1) were found to be significant in distinguishing A. grahami. Further, we established three machine learning models, including SVM, KNN, and RF, to analyze spectra from different waveband groups. The biological fingerprint region (1800–1300 cm−1) demonstrated a substantial advantage in identifying empty puparium species. Remarkably, the SVM model exhibited an impressive accuracy of 100 % in identifying all five fly species. This study represents the first instance of employing infrared spectroscopy and machine learning methods for identifying insect species using empty pupariums, providing a robust research foundation for future investigations in this area.

Carbohydrate Core-Shell Electrosprayed Microcapsules for Enhanced Oxidative Stability of Vitamin A Palmitate.

Vitamin A is an essential micronutrient that is readily oxidized. In this study, the encapsulation of vitamin A palmitate (AP) within a core-shell carbohydrate matrix by co-axial electrospray and its oxidative stability was evaluated. The electrosprayed core-shell microcapsules consisted of a shell of octenyl succinic anhydride (OSA) modified corn starch, maltose (Hi-Cap), and a core of ethyl cellulose-AP (average diameter of about 3.7 µm). The effect of different compounds (digestion-resistant maltodextrin, soy protein hydrolysate, casein protein hydrolysate, and lecithin) added to the base core-shell matrix formulation on the oxidative stability of AP was investigated. The oxidative stability of AP was evaluated using isothermal and non-isothermal differential scanning calorimetry (DSC), and Raman and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy methods. The core-shell carbohydrate matrix minimizes the amount of AP present at the microparticle surface, thus protecting AP from oxidation. Furthermore, the most effective oxidation protection was achieved when casein protein hydrolysate was added to the core of the microcapsule due to hydrophobic and hydrogen bond interactions with AP and by the resistant maltodextrin in the shell, which acted as a filler. The utilization of ethanol as a solvent for the dispersion of the core compounds increased the hydrophobicity of the hydrolyzed proteins and contributed to the enhancement of their antioxidant ability. Both the carbohydrate core-shell microcapsule prepared by co-axial electrospray and the addition of oxidation protection compounds enhance the oxidative stability of the encapsulated AP.

Konwersja etanolu do acetonu na katalizatorze ZnO-CaO w obecności pary wodnej

The main product of the conversion of ethanol to acetone on a ZnO-CaO catalyst is acetone, the yield of which strongly depends on the composition of the reaction environment. When oxygen is present, the yield of products of destructive and complete oxidation increases greatly. In contrast, when water vapor is present, both the selectivity and conversion of ethanol increase. Therefore, the conversion of ethanol is the limiting step in the overall process, which determines the selectivity of the conversion of ethanol to acetone. In this regard, it appeared suitable to investigate the effect of introducing water to the contact zone. As experiments indicated, the addition of water caused a significant effect on the conversion, selectivity, and acetone yield on the ZnO-CaO catalyst. As the partial pressure of water vapor increases, the conversion of ethanol and the acetone yield increase, while the yield of carbon dioxide decreases. The decrease in carbon dioxide is associated not only with the inhibition of the conversion of ethanol to CO2. In this study, the adsorption of water vapor and ammonia on the surface of the ZnO-CaO catalyst was examined by infrared spectroscopy method. It has been shown that water vapor at low temperatures is adsorbed on the catalyst surface in the molecular form, while at higher temperatures it is adsorbed in the dissociative form. Co-transformation reactions of ethanol with acetic acid, acetaldehyde with ethylene, and acetaldehyde with acetic acid have been studied. The obtained results indicated that acetone is formed mainly through the stage of complexation of acetaldehyde with ethylene. The isomerization reaction of 1-butene to 2-butene has been investigated. It was found that the yield of cis-2-butene in the absence of water vapor is higher, likely attributed to the molecular adsorption of water on Lewis centers. Based on these findings, a scheme for the vapor-phase conversion of ethanol into acetone on the studied catalysts was formulated.

Exploring salivary exosomes as early predictors of oral cancer in susceptible tobacco consumers: noninvasive diagnostic and prognostic applications.

Salivary exosome analysis provides a noninvasive and comprehensive approach with potential applications in oral cancer diagnosis and prognosis. The early detection of oral cancer has remained a critical concern in enhancing the quality of life, especially for individuals who consume tobacco and are at greater risk of developing the disease. The current study investigates the potential of salivary exosomes in screening smokers for early signs and transformations of oral cancer. Morphological characterization of salivary exosomes among three study groups (non-smokers as control, smokers as high-risk tobacco consumers, and Oral cancer) (n = 120) was carried out through dynamic light scattering, and nanoparticle tracking analysis. For molecular characterization, EXOCET and Fourier transform infrared spectroscopy methods were utilized. The expression of the exosomal surface protein CD63 was evaluated using Western blotting. Salivary exosomes exhibit noticeable differences in size between control group and tobacco consumers. The differentiation extended beyond exosome size and included variations in concentration and bio-molecular composition, as determined by FTIR screening. Tobacco consumers and oral cancer groups showed significantly larger and more concentrated exosomes compared to the healthy group. Our study provides strong evidence that the properties of salivary exosomes can serve as reliable noninvasive biomarkers for distinguishing tobacco consumers from non-smokers and oral cancer patients. Our results underscore the potential of exosome-based diagnostics in early oral cancer detection for high-risk individuals. The larger size and higher concentration of exosomes in tobacco consumers indicate early changes in cell secretions associated with the transformation from healthy to abnormal cells.

Temperature-Sensitive Hydrogels as Carriers for Modulated Delivery of Acetaminophen.

The purposes of this study are the polymerization of temperature-sensitive copolymers based on N-isopropyl acrylamide and 10 mol % of 2-hydroxypropylmethacrylate, characterisations of their thermal, morphological and swelling properties, as well as the analysis of potential application in drug-delivery systems. Acetaminophen, the representative of non-steroidal anti-inflammatory drugs, was used as a model drug in this study. It is a common pain relief drug, which is also used for fever treatment. However, oral administration comes with certain health risks, mainly the overdose and frequent administration of up to four times a day. The goal of applying temperature-sensitive hydrogel is to enable extended administration once a day, depending on the body temperature. The swelling behavior of the obtained poly(N-isopropyl acrylamide-co-2-hydroxypropylmethacrylate) (p(NIPA/HPMA)) hydrogels and their temperature-sensitivity, kinetics and order of swelling processes at 18 and 38 °C were analyzed. The thermal properties of these hydrogels were observed by the DSC method, and the obtained thermograms showed both melting and glass transitions. The drug delivery system of p(NIPA/HPMA) hydrogels with loaded acetaminophen was analyzed using scanning electron microscopy and Fourier transform infrared spectroscopy methods. Structural analysis of FTIR spectra indicates that non-covalent intermolecular interactions of the type of hydrogen bonds were formed among functional groups of acetaminophen and side-chains of p(NIPA/HPMA) hydrogels. The surface structure of p(NIPA/HPMA) hydrogels after drug loading indicates the acetaminophen presence into the pores of the hydrogel network, and their loading efficiency was higher than 92%. Qualitative and quantitative analysis of acetaminophen, determined by the high-pressure liquid chromatography method, showed that about 90-99% of the loaded amount was released from p(NIPA/HPMA) hydrogels within 24 h. Kinetic parameters of the acetaminophen release under simulated gastrointestinal conditions were determined. Based on obtained results, the drug delivery system of temperature-sensitive p(NIPA/HPMA) hydrogels with loaded acetaminophen could be suitable for additional investigation for modulated drug administration, e.g., for extended drug administration.

Early diseases diagnosis in body fluids (serum and saliva) using infrared spectroscopy

Infrared spectroscopy it is becoming more and more useful in the field of biomedical research. Infrared spectroscopy has been used more and more to characterize biological matrixes, providing a simple way to obtain diagnostic and observational information from easily acquired samples. These tests are performed in order to monitor the changes, and in this way to characterize the biological matrix, with the aim of detecting the first signs that can diagnose a disease. Vibrational spectroscopy analysis of biological fluids has become more and more popular recently. Notably, the development of infrared spectroscopic screening of blood products, particularly blood serum and saliva, for illness diagnosis has attracted economic attention. This review examines some applications of the infrared spectroscopy method that was employed to examine human serum in order to detect disease at an early stage, published between 2017 and 2022.

Vibrational spectroscopy of neutral and cationic 2-Methoxyethanol

Hydrogen bonding interactions, such as the O-H···O interaction, play a crucial role in stabilizing conformations of both organic and biological molecules. In this study, we employed the infrared (IR)–vacuum-ultraviolet (VUV) non-resonant ionization detected IR spectroscopy (NRID-IR) method to investigate the molecular structure of neutral and cationic 2-methoxyethanol (CH3OCH2CH2OH, 2-ME). The stable structures and anharmonic IR spectra of neutral and cationic 2-ME were calculated using density functional theory (DFT) at the B3LYP-D3(BJ)/def2-TZVPP level. Our results revealed that the two most stable conformers of neutral 2-ME exhibit a weak O-H···O intramolecular hydrogen bond, while the cationic 2-ME lacks the O-H···O interaction but contains a C-H···O intramolecular hydrogen bond. A comparison of the experimental and theoretical IR absorption spectra reveals that the most stable conformer (gauche-(anti-gauche)-trans) is the primary contributor to the observed IR spectra of neutral 2-ME in the 2700–7250 cm−1 range. Similarly, the second stable conformer is found to be the dominant contributor to the observed IR spectra of cationic 2-ME in the range of 2700–7100 cm−1. Additionally, the C-H fundamental stretching mode of cationic 2-ME is found to be blue-shifted by approximately 100 cm−1 compared to that of neutral 2-ME. Furthermore, the natural bond orbital (NBO) analysis suggests that in neutral 2-ME, the n(O)→σ*(CαH) interactions result in significant negative hyperconjugation, leading to the weakening of CαH bonds and a subsequent reduction in vibrational energy.

Development of feature extraction method for near infrared spectroscopy using stepwise bayesian linear regression

Near infrared (NIR) spectra contain information regarding the analyte as well as uninformative wavelengths. To build high-performance data-driven models, key wavelengths with a strong correlation to the analyte must be selected. This study proposes a feature selection method called stepwise Bayesian linear regression (SBLR) for eliminating unrelated wavelengths, thereby enhancing the robustness of the constructed model. First, a random wavelength is selected from an optimal variable set, and the other wavelengths are placed in a candidate variable set. A Bayesian linear regression (BLR) is implemented by adding a new variable from the candidate set or removing a variable from the optimal set in each step. Furthermore, the BLR model is utilized to perform the F-test. Comparing with the critical value of the F-test with a significance level of α, the test determines whether the variable is retained in the optimal set. Finally, the extracted variables are used to construct a BLR model. The performance and generalization ability of the proposed method were validated. The physical explanation of extracted wavelengths is consistent with the perspective of chemical analysis based on the experiment, which provides a good understanding of the collected NIR spectral data. In addition, compared with traditional algorithms, such as partial least squares regression, least absolute shrinkage and selection operator, and stepwise regression, the proposed method reserves only a few of the effective wavelengths from the full NIR spectra. The proposed method demonstrates potential for key wavelength selection in NIR spectroscopy.

Effects of long-term tillage practices on the stability of soil aggregates and organic carbon in black soil farmland.

We examined the effects of different tillage practices on plough layer soil structure and organic carbon stabilization in black soil farmland with a long-term positioning platform. The wet-sieving method and infrared spectroscopy method were used to investigate the impacts of conventional tillage (CT), no-tillage (NT), sub-soiling tillage (ST), and moldboard plowing tillage (MP) on soil aggregates distribution and organic carbon characteristics in 0-40 cm soil layers. Compared to CT, both NT and ST treatments significantly increased the proportion of large macroaggregates (>2 mm) in the topsoil layer (0-20 cm)and that of small macroaggregates (0.25-2 mm) in the subsoil layer (20-40 cm) for NT, ST, and MP. NT, ST, and MP treatments resulted in higher mean weight dia-meter (MWD) and mean geometric diameter (GMD) of soil aggregates in both the topsoil and subsoil layers. NT treatment improved organic carbon contents in bulk soil and large macroaggregates in the topsoil layer, while ST and MP enhanced organic carbon contents in bulk soil and large macroaggregates in the subsoil layer. The contribution rate of small macroaggregates organic carbon content to the total was between 68.9% and 83.4%. Furthermore, the organic carbon chemical stabilization of soil body and aggregates increased in the topsoil and subsoil layers under NT treatment compared to others. The MWD had a positive correlation with the organic carbon content and chemical stability of soil body and small macroaggregates. These findings offered a theoretical basis for understanding the impacts of different tillage practices on the stability of soil aggregate and organic carbon in black soil region.

Crystal Chemistry, Thermal and Radiation-Induced Conversions and Indicatory Significance of S-Bearing Groups in Balliranoite

Crystal-chemical features of a sulfide-bearing variety of the cancrinite-group mineral balliranoite from the Tuluyskoe lapis lazuli deposit, Baikal Lake area, Siberia, Russia, have been investigated using a multimethodic approach based on infrared (IR), Raman, and electron spin resonance (ESR), as well as ultraviolet, visible and near infrared (UV–Vis–near IR) absorption spectroscopy methods, luminescence spectroscopy, electron microprobe analysis, selective sorption of CO2 and H2O from annealing products, and single-crystal X-ray structure analysis. Holotype balliranoite and its sulfate analogue, davyne, were studied for comparison. The crystal-chemical formula of the studied sample from Tultuyskoe is Na5.4K0.1Ca2.4(Si6Al6O24)Cl2[(CO3)0.7(SO4)0.18S*0.95Cl0.1(H2O)0.16], where the content of the wide zeolite channel is given in square brackets; S* is total sulfide sulfur occurring as disordered S2●−, cis- and trans-S4, S52−, minor S3●−, and HS− groups. The presence of S52− and HS− groups, the absence of CO2 molecules, and the association with pyrrhotite and Fe-free pargasite indicate that the studied sample crystallized under highly reducing, low-temperature conditions, unlike holotype balliranoite whose formation was related to the Somma-Vesuvius volcanic complex, Italy. Irradiation of balliranoite from Tultuyskoe with X-rays results in the transformations of polysulfide groups other than S3●− into S3●− in accordance with the scheme: S52− → S2●− + S3●−; 3S2●− → 2S3●− + e−; S4 + S2●− + e− → 2S3●−; S4 + S2●− + e− → 2S3●−; S4 + S52− + e− → 3S3●− (e− = electron).