Search Results (203)

Nucleophilic ring-opening of bis(oxiranes), containing several reactive centers, can be used to elaborate straightforward atom-economy and stereoselective approaches to polyfunctionalized compounds. In the present work, ring-opening of cis- and trans-diastereomers of a spirocyclic bis(oxirane), containing a cyclooctane core (namely, 1,8-dioxadispiro[2.3.2.3]dodecane), upon treatment with various amines, was studied. Trans-isomer afforded aminoalcohols with 9-oxabicyclo[3.3.1]nonane moiety, formed via domino-process, including opening of an oxirane ring followed by intramolecular cyclization. Ring-opening of cis-isomer gave aminosubstituted cis-cyclooctane-1,5-diols, derived from independent reaction of two oxirane moieties. Activation of oxirane rings by the addition of LiClO₄, acting as a Lewis acid, allowed the involvement of a number of primary and secondary aliphatic amines as well as aniline derivatives in the reaction. Scope and limitations of the reaction were studied and a series of aminoalcohols with a 9-oxabicyclo[3.3.1]nonane core and symmetric diaminodiols with a cyclooctane core were obtained. Full article

This study aimed to analyze the volatile organic compounds (VOCs) for different rice aroma types using sensory evaluation, headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS), and gas chromatography-ion mobility spectrometry (GC-IMS) techniques, and to explore the material basis for the flavor differences. Based on the sensory evaluation results, rice aroma was categorized into three types, distinguished by their unique aroma compounds. Type A was characterized by a prominent sweet, popcorn aroma, type B by a more prominent cereal and starchy flavor, and type C by a more complex aroma. Untargeted metabolomics analysis using HS-SPME-GC-MS identified and characterized 74 volatile compounds. A comparison of A versus B versus C revealed 8 key aroma compounds, primarily alkanes, aldehydes, ketones, alcohols, and heterocyclic compounds. (E)-2-Octenal, 6-Undecanone, 2-Acetyl-1h-pyrrole, and P-menthan-1-ol in type A gave it a better sweet aroma, Dodecane, 2,6,10-trimethyl-, 1-Octen-3-one, and 2-Methyldecane in type B gave it a better starchy and cereal flavor. 2-Acetyl-1h-pyrrole, Heptacosane, and 1-Propanol in type C contributed to a complex aroma. GC-IMS analysis showed that the fingerprints of rice with different aroma types were significantly different. The VOCs of aroma type A contained (+)-limonene, 2-methylpyrazine, 2-pentanone, ethyl butanoate, n-pentanal, styrene, 1-butanol, 3-methyl-, acetate, 1-hexanal, 1-pentanol, and 2-heptanone, which gave it a better sweet aroma. The VOCs of aroma type C contained 1-octen-3-ol, 2,6-dimethyl pyrazine, 2-acetylpyridine, and ethyl hexanoate, which gave it a better complex aroma. Full article

Coal slime, a byproduct of coal processing with high ash content, poses significant challenges in terms of its efficient separation and resource utilization due to its fine particle size and complex composition. This study aims to optimize the oil agglomeration process for coal slime separation through systematic parameter investigation and predictive modeling. Response surface methodology (RSM) was employed to analyze the individual and interactive effects of pulp density, oil dosage, and agitation rate on three key performance indicators: combustible recovery, efficiency index, and ash rejection. Meanwhile, an artificial neural network (ANN) was developed to establish a robust prediction model for the efficiency index. The novelty of this work lies in the integration of thermodynamic analysis, multi-objective optimization, and machine learning approaches. The key findings include the identification of dodecane as the optimal bridging liquid due to its intermediate carbon chain length that balances interfacial tension and wettability. Under optimized conditions (14% pulp density, 22% oil dosage, and 1600 r/min), the process achieved a combustible recovery of 91.49%, ash rejection of 61.58%, and efficiency index of 53.07%. The ANN model demonstrated superior predictive capability with an overall R² of 0.9659 and RMSE of 1.12. This work provides comprehensive guidelines for the design, optimization, and scale-up of coal slime oil agglomeration processes in industrial applications. Full article

Due to growing environmental challenges, many studies are focusing on vegetable-based lubricants. Industrial lubricants pose a significant risk to the environment and human health. The tribological performances of calophyllum calaba (galba) and avocado when used as a base oil and as a liquid additive were compared to those of moringa oil. The different lubricant formulations were investigated under an ambient atmosphere, using a reciprocating ball-on-plane tribometer in a boundary lubrication regime. Graphite particles were used as solid lubricant additives due to their excellent friction performances in these formulations. Dodecane was the mineral oil used as a reference and base oil in some lubricant formulations. It was found that the percentage used and the fatty acid molecule composition of vegetable oils have an important influence on the tribological performances of the different formulations. The presence of oleic acid molecules shows a positive effect but is not sufficient to explain the friction reduction obtained with moringa oil. The triglyceride shape of an oleic acid molecule is the key to an important friction reduction, despite the small amount (2 wt% as liquid additive) in lubricant formulations. Full article

Given that olive oil produced in the Ionian islands has not been extensively studied, forty-seven olive oil samples of the Koroneiki olive cultivar were collected from Zakynthos, Kerkyra, Kefalonia, and Leukada, which comprise well-known islands of the Ionian Sea. The samples were subjected to analysis of volatile compounds using headspace solid-phase microextraction coupled to gas chromatography–mass spectrometry (HS-SPME/GC-MS). Based on HS-SPME/GC-MS analysis, twenty-five volatile compounds were tentatively identified and semi-quantified using the internal standard method. Volatile compounds included alcohols, aldehydes, benzene derivatives, esters, hydrocarbons, ketones, and terpenoids. The application of descriptive data analysis, such as multivariate analysis of variance (MANOVA), linear discriminant analysis (LDA), and factor analysis (FA), to the semi-quantitative data (μg/L) of the identified volatile compounds resulted in the extraction of key volatile compounds that differentiated olive oil samples of the Koroneiki olive cultivar according to geographical origin. The cross-validation method of LDA showed a prediction rate of 83.0%, whereas the variance explained by FA was approximately 69.06% (69.055%). The key volatile compounds that were associated most with the geographical origin of olive oil samples were (Z)-1,3-pentadiene, dodecane, 2,2,4,6,6-pentamethyl-heptane, 3-ethyl-1,5-octadiene, 2,4-dimethyl-heptane, 4-methyloctane, ethanol, 2-hexanol, and 3-methylbutanal, among others. The study contributes to the regional features of olive oil of the Koroneiki olive cultivar from the Ionian islands based on key volatile compounds and further supports the consecutive research of the international community regarding olive oil authentication. Full article

The present study explores novel alternatives for the exploitation of sugarcane bagasse ash by obtaining and modifying SiO₂ nanoparticles through a green synthesis method. The hydrophilic nature of the nanoparticles was modified using oleic acid. The nanoparticles were characterized using FTIR, FESEM, and DLS, and their performance in the stabilization of Pickering emulsions was also studied. FESEM micrographs of the nanoparticles revealed an irregular and agglomerated structure. EDS confirmed that their main components are oxygen and silicon, and ATR-FTIR spectra demonstrated that oleic acid effectively modified the nanoparticles. Subsequently, O/W Pickering emulsions were fabricated by combining rotor–stator homogenization and probe ultra-sonication, using dodecane and liquid paraffin as model oil phases and SiO₂ NPs as stabilizers. Static light scattering measurements showed that the emulsions exhibited polydispersity, while photographic monitoring confirmed that their physical stability was affected by the concentrations of oleic acid and nanoparticles: concentrations of up to 20.0 wt% and 1.0 wt%, respectively, produced emulsions that remained stable for 7 to 15 days. This study identifies the behavior and challenges associated with novel pathways for the valorization of sugarcane bagasse ash. The stabilization of Pickering emulsions using the obtained SiO₂ NPs highlights their potential in pharmaceutical, cosmetic, and food applications. Full article

Background: Early cancer detection remains a critical challenge in clinical oncology, requiring further development of innovative diagnostic methods with improved sensitivity and specificity. This study addresses the issue by investigating the potential of exhaled air metabolome analysis, using highly porous carbon material for sample collection, as a promising approach for the early diagnosis of laryngeal cancer. Volatile organic compounds (VOCs) present in exhaled breath are known to reflect underlying metabolic changes. This research explores the feasibility of using VOC-derived metabolomic signatures as non-invasive biomarkers for cancer detection. Methods: The primary objective was to evaluate exhaled air metabolome analysis as a diagnostic tool for individuals at risk of respiratory tract malignancies. The study involved 36 participants, including 13 patients diagnosed with laryngeal cancer and 23 healthy individuals serving as a control group. Breath samples were collected using a highly porous carbon material, selected for its superior sorption properties, enabling efficient capture and stabilization of VOCs. These samples were subsequently analyzed using gas chromatography-mass spectrometry (GC-MS) to identify and compare VOC patterns between the two groups. Results: Preliminary analysis revealed apparent differences in VOC profiles between cancer patients and healthy individuals, with cancer patients exhibiting elevated peak intensities for specific metabolites such as diethyl phthalate, nonadecane, and trimethyl-dodecane. Multivariate analysis using principal component analysis (PCA) demonstrated separation between the two groups, reflecting systematic differences in exhaled VOC signatures. Conclusions: This initial study supports the potential of breath VOC profiling for laryngeal cancer detection, laying the groundwork for further validation and refinement of this diagnostic approach. The use of porous carbon material facilitated efficient VOC capture, supporting its role in non-invasive breath analysis. Full article

Understanding the microscopic occurrence states of shale oil—particularly the distribution between adsorbed and free phases—is essential for optimizing the development of unconventional reservoirs. In this study, we propose an integrated methodology that combines experimental techniques with molecular dynamics simulations to investigate shale oil behavior within kerogen nanopores. Specifically, pyrolysis–gas chromatography–mass spectrometry (PY-GC-MS), solid-state ¹³C nuclear magnetic resonance (¹³C NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were performed to construct a representative kerogen molecular model based on shale samples from the Lianggaoshan Formation in the Sichuan Basin. Grand Canonical Monte Carlo (GCMC) simulations and a theoretical occurrence model were applied to quantify the adsorption characteristics of n-dodecane under varying pore sizes, temperatures, and pressure. The results show that temperature exerts a stronger influence than pore diameter on adsorption capacity, with adsorption decreasing by over 50% at higher temperatures, and pressure has a limited effect on the adsorption amount of dodecane molecules. This study offers a robust workflow for evaluating shale oil occurrence states in complex pore systems and provides guidance for thermal stimulation strategies in tight oil reservoirs. Full article

The ability to predict the vapor pressure and vapor-phase composition of hydrocarbon mixtures (such as jet fuel, sustainable aviation fuel or its un-refined precursors) and partially vaporized hydrocarbon mixtures is important to simulations of processes that involve vaporization such as distillations, flash points, combustion properties of partially vaporized fuels, etc. Raoult’s Law provides a simple algebraic formula relating liquid composition and temperature to vapor composition and pressure. However, Raoult’s Law is not accurate at low mole fractions, which is typical for complex mixtures such as fuels. A common approach to correcting Raoult’s Law is to apply a scale factor, a so-called activity coefficient. Numerous models exist for predicting activity coefficients. Here we benchmark against the UNIFAC model, which predicts activity coefficients based on mole fractions, group fractions, Van der Waals volume and surface area and temperature-dependent interaction terms between groups. While this approach is truly predictive, its accuracy at very low mole fractions has not been validated, and it is computationally intensive, particularly for simulations (especially optimizations) that require vapor composition or pressure within the inner-most loop. Here we present an alternative correction to Raoult’s law, where the vapor pressure of the i^th component is represented by a modified form of the Clausius–Clapeyron equation. The reference temperature ($T_{ref}$) is replaced by a simple algebraic function that converges to $T_{ref}$ as $x_i$ approaches 1 while smoothly increasing from this value as $x_i$ decreases. Simultaneously, the heat of vaporization ($\mathsf{\Delta }{H}_{vap,i}\left(T\right)$) term is replaced by another simple algebraic expression that converges to $\mathsf{\Delta }{H}_{vap,i}\left(T\right)$ as $x_i$ approaches 1 while smoothly decreasing as $x_i$ decreases. In this model, the temperature-dependent heat of vaporization is tuned at each temperature such that the Clausius–Clapeyron equation reproduces the correct vapor pressure of the neat material, while the parameterized algebraic corrections are tuned to vapor pressure data of mixtures involving n-pentane, toluene, and dodecane, where the mole fractions of n-pentane and toluene are maintained below 10%_mol. Validation of the resulting model is accomplished by comparing modeled vapor–liquid equilibrium systems with experimental measurements. This approach improves the accuracy and computational efficiency of volatility predictions, thereby supporting the development, certification, and adoption of sustainable aviation fuel. Full article

Arnica montana L. (mountain arnica) is a medicinal plant with diverse biological activities commonly used in pharmacy and cosmetics. The attributes of A. montana are related to e.g., the concentration and chemical composition of its essential oils (EOs). Therefore, the objective of this study was to: (i) characterize the chemical composition of EOs obtained from mountain arnica flower heads, rhizomes, and roots used as a pharmacopoeial material, (ii) demonstrate the effects of particular EO types and their combinations on antibacterial activity, and (iii) demonstrate the effect of the presence of A. montana EOs and their combinations with commercial antibiotics on their antibacterial activity. Essential oils obtained by hydrodistillation from different parts of A. montana were screened for their chemical composition and antibacterial properties. The chemical composition of the EOs was determined using the GC–MS technique. E-caryophyllene, caryophyllene oxide, germacrene D, farnesyl acetate, and dodecanal were the main components of the EO distilled from the flower heads. In turn, 2,5-dimethoxy-p-cymene, 2,6-diisopropylanisole, p-methoxyheptanophenone, and thymol methyl ether were the main molecules detected in the EO from the A. montana rhizomes and roots. The data clearly indicate that the presence of mountain arnica EO alone and in the interaction with commercial antibiotics (amoxicillin, ciprofloxacin, metronidazole) has a beneficial effect on their antibacterial activity. Full article

Restricting the use of chemical pesticides in forestry requires the search for alternative solutions. These could be volatile organic compounds produced by three investigated species of bacteria (Bacillus amyloliquefaciens (ex Fukumoto) Priest, B. subtilis (Ehrenberg) Cohn and B. thuringiensis Berliner), which inhibit the growth of the pathogen F. oxysporum Schltdl. emend. Snyder & Hansen in forest nurseries. The highest inhibition of fungal growth (70%) was observed with B. amyloliquefaciens after 24 h of antagonism test, which had a higher content of carbonyl compounds (46.83 ± 8.41%) than B. subtilis (41.50 ± 6.45%) or B. thuringiensis (34.62 ± 4.77%). Only in the volatile emissions of B. amyloliquefaciens were 3-hydroxybutan-2-one, undecan-2-one, dodecan-5-one and tetradecan-5-one found. In contrast, the main components of the volatile emissions of F. oxysporum were chlorinated derivatives of benzaldehyde (e.g., 3,5-dichloro-4-methoxybenzaldehyde) and chlorinated derivatives of benzene (e.g., 1,4-dichloro-2,5-dimethoxybenzene), as well as carbonyl compounds (e.g., benzaldehyde) and alcohols (e.g., benzyl alcohol). Further compounds were found in the interactions between B. amyloliquefaciens and F. oxysporum (e.g., $\alpha$-cubebene, linalool, undecan-2-ol, decan-2-one and 2,6-dichloroanisole). Specific substances were found for B. amyloliquefaciens (limonene, nonan-2-ol, phenethyl alcohol, heptan-2-one and tridecan-2-one) and for F. oxysporum (propan-1-ol, propan-2-ol, heptan-2-one and tridecan-2-one). The amounts of volatile chemical compounds found in B. amyloliquefaciens or in the bacterium–fungus interaction can be used for further research to limit the pathogenic fungus. In the future, one should focus on the compounds that were found exclusively in interactions and whose content was higher than in isolated bacteria. In order to conquer an ecological niche, bacteria increase the production of secondary metabolites, including specific chemical compounds. The results presented are a prerequisite for creating an alternative solution or supplementing the currently used methods of plant protection against F. oxysporum. Understanding and applying the volatile organic compounds produced by bacteria can complement chemical plant protection against the pathogen, especially in greenhouses or tunnels where plants grow in conditions that favour fungal growth. Full article

Background: Insulin resistance (IR) is an underlying pathophysiology for type 2 diabetes (T2D). The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) is the simplest method for evaluating IR. At the same time, volatile organic compounds (VOCs) detected in human respiration can be correlated with specific diseases. To date, machine learning (Mach-L) has yet to be used to examine potential relationships between VOCs and IR. The present study has two aims: (1) to identify the VOCs most relevant to HOMA-IR, and (2) to use Shapley addictive explanation (SHAP) to determine the impacts of the distributions and directions of each feature in Taiwanese women. Methods: A total of 1432 Taiwanese women between the ages of 19 and 84 years were enrolled, and 344 VOCs were measured. Traditional multiple linear regression (MLR) was used as a benchmark for comparison, applying three Mach-L methods. Finally, SHAP was used to evaluate the directions of impacts of the features on HOMA-IR. Results: Six VOCs were identified as important: dimethylfuran, propanamine, aniline, butoxyethanol, and isopropyltoluene, in order from most to least important. SHAP found that dimethylfuran, isopropyltoluene, and dodecane were positively correlated to HOMA-IR, while butoxyethanol, aniline, and propanamine were negatively correlated. Conclusions: Using three different Mach-L methods, six VOCs were selected to be related to IR in Taiwanese women. According to their importance, dimethylfuran, propanamine, aniline, butoxyethanol, and isopropyltoluene could be used to help diagnose HOMA-IR. Furthermore, by using SHAP, dimethylfuran, isopropyltoluene, and dodecane had a positive and the other three had a negative influence. Full article

Thrips can be attracted or repelled by volatiles from different host plant species. Houttuynia cordata is a common plant species with a strong, offensive smell, and few pests have been detected on this plant. Here, the olfactory responses of Frankliniella occidentalis to H. cordata volatiles were tested using electroantennography (EAG) and behavioral bioassays in different types of olfactometers, and the behavioral responses of Orius similis, a natural enemy of F. occidentalis, to the related main volatile compounds were also evaluated. Y-tube olfactometer bioassays showed that F. occidentalis performed negative responses to H. cordata volatiles. Decanal (47.21%), 1-decanol (11.02%), dodecanal (7.13%), β-myrcene (5.12%), and decanoyl acetaldehyde (3.76%) were the more abundant components in the H. cordata volatile profile in gas chromatography–mass spectrometry analysis. EAG recordings showed that the antennae of female thrips could perceive these five compounds at a wide range of concentrations. In six-arm olfactometer bioassays, F. occidentalis exhibited negative responses to decanal, dodecanal, and decanoyl acetaldehyde at various doses but performed positive responses to 1-decanol and β-myrcene at certain doses. Furthermore, decanal, dodecanal, and decanoyl acetaldehyde at all concentrations showed no significant influences on the behavioral responses of O. similis. According to the results above, H. cordata can be a repellent plant species to F. occidentalis, and decanal, dodecanal, and decanoyl acetaldehyde show great potential for development as repellents for the control of F. occidentalis. In short, our results suggest that an integrated pest management system combining H. cordata-derived biopesticides with releases of the predator O. similis could effectively control F. occidentalis. Full article

To address the design and optimization of the ignition system for the microgravity single-droplet combustion experiment module within the Combustion Science Experimental System (CSES) aboard the Chinese Space Station (CSS), it is essential to first determine the ignition temperatures required for typical liquid fuel droplets. In this study, ignition experiments were conducted on droplets of three representative hydrocarbon fuels—ethanol, n-heptane, and n-dodecane—in static air at high temperatures ranging from 760 K to 1100 K. The experimental results show that the initial droplet diameter is inversely correlated with the ambient temperature at which ignition occurs. Subsequently, based on Frank-Kamenetskii’s analytical method and combined with experimental data, a semi-empirical predictive model for droplet ignition temperatures in a normal-gravity environment was derived. Building upon this, and considering the characteristics of the microgravity environment, an appropriate empirical formula was applied to refine the model, resulting in a predictive model for droplet ignition temperatures in the microgravity environment. Furthermore, by comparing the experimental data and the observed phenomena from existing microgravity experiments, this semi-empirical predictive model used in the microgravity environment effectively reflects the trend of droplet ignition temperature variations. Full article

This paper investigates the influence of ventilation conditions, including oxidizer flow speed and oxygen concentration, on major species composition in favor of estimating a risk of flame acceleration at reduced gravity. A two-step chemical reaction for gas phase and a soot formation model based on laminar smoke point are used. To calculate thermal radiation from flame, a discrete-ordinates method is coupled with a non-grey model by taking into account the radiative properties of CO, CO₂, H₂O and soot. The predictions provide further insights into the intimate coupling of fuel types, such as heptane and dodecane, with burning rate, flame structure and toxic emissions as a consequence of changes in ventilation conditions such as oxidizer flow velocity and oxygen concentration. From a boundary-layer microgravity flame, the CO₂ to CO ratio is less than 3, and the unburnt hydrocarbons C_mH_n to CO ratio is less than 2, with a concentration of unburnt fuel that exceeds the Lower Flammability Limit. This finding on the production of unburnt species is contrasted to the case of a buoyancy-controlled flame at Earth gravity. Full article