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• BVOCs emissions in a subtropical pristine forest of southern China were measured in situ by using dynamic branch enclosures. • Representative mature evergreen trees were measured at four altitudes. • Monoterpenes were the dominant BVOCs emitted by most broad-leaved trees. • Localized emission factors of speciated BVOCs were obtained. Emission characteristics of biogenic volatile organic compounds (BVOCs) from dominant tree species in the subtropical pristine forests of China are extremely limited. Here we conducted in situ field measurements of BVOCs emissions from representative mature evergreen trees by using dynamic branch enclosures at four altitude gradients (600–1690 m a.s.l.) in the Nanling Mountains of southern China. Composition characteristics as well as seasonal and altitudinal variations were analyzed. Standardized emission rates and canopy-scale emission factors were then calculated. Results showed that BVOCs emission intensities in the wet season were generally higher than those in the dry season. Monoterpenes were the dominant BVOCs emitted from most broad-leaved trees, accounting for over 70% of the total. Schima superba, Yushania basihirsuta and Altingia chinensis had relatively high emission intensities and secondary pollutant formation potentials. The localized emission factors of isoprene were comparable to the defaults in the Model of Emissions of Gases and Aerosols from Nature (MEGAN), while emission factors of monoterpenes and sesquiterpenes were 2 to 58 times of those in the model. Our results can be used to update the current BVOCs emission inventory in MEGAN, thereby reducing the uncertainties of BVOCs emission estimations in forested regions of southern China. [Display omitted] [ABSTRACT FROM AUTHOR]

Bioactive peptides are short amino acid sequences that play important roles in various physiological processes, including antioxidant and protective effects. These compounds can be obtained through protein hydrolysis and have a wide range of potential applications in a variety of areas. However, despite the potential of these compounds, more in-depth knowledge is still necessary to better understand details regarding their chemical reactivity and electronic properties. In this study, we used molecular modeling techniques to investigate the electronic structure of isolated amino acids (AA) and short peptide sequences. Details on the relative alignments between the frontier electronic levels, local chemical reactivity and donor–acceptor properties of the 20 primary amino acids and some di- and tripeptides were evaluated in the framework of the density functional theory (DFT). Our results suggest that the electronic properties of isolated amino acids can be used to interpret the reactivity of short sequences. We found that aromatic and charged amino acids, as well as Methionine, play a key role in determining the local reactivity of peptides, in agreement with experimental data. Our analyses also allowed us to identify the influence of the relative position of AA and terminations on the local reactivity of the sequences, which can guide experimental studies and help to propose/evaluate possible mechanisms of action. In summary, our data indicate that the position of active sites of polypeptides can be predicted from short sequences, providing a promising strategy for the synthesis and bioprospection of new optimized compounds. [ABSTRACT FROM AUTHOR]

Fukui functions are related to electron densities, and their interpretation permits the determination of reactivity of atomic centres. However, negative values cannot be interpreted by an "electron density based" model and represent a phenomenon that has been little investigated and understood. Previous works in the literature suggest that they are related to nodes in the wave function. In our investigations we can relate negative values to nitro groups and their position on aromatic systems, as it is a moiety with HOMO electron densities close to "0" related to "electron attracting" groups. This work can help us understand and predict this phenomenon and the associated chemical reactivities. We also pay attention to the influence of the nitro group angle vs. the aromatic ring. [ABSTRACT FROM AUTHOR]

In this work, we introduce the q-Rényi's divergence, which results from the conjunction of Rényi's divergence and Jackson's integral. The resultant equation can be employed as a measure of chemical similarity, which consists of comparing two or more chemical species with a set of molecules that have been characterized to find two or more molecules that could have similar chemical or physical properties. To carry out our study, we applied q-Rényi's divergence using a set of Tetrodotoxin variants and a set of 1641 organic molecules. Our results suggest that q-Rényi's divergence could be a valuable tool to complement chemical similarity studies. [ABSTRACT FROM AUTHOR]

Context: The analysis of the changes in the electronic structure along intrinsic reaction coordinate (IRC) paths for model reactions: (i) ethylene + butadiene cycloaddition, (ii) prototype SN2 reaction Cl− + CH3Cl, (iii) HCN/CNH isomerization assisted by water, (iv) CO + HF → C(O)HF was performed, in terms of changes in the deformation density (Δr) and the deformation of MEP (ΔMEP). The main goal was to further examine the utility of the ΔMEP as a descriptor of chemical bonding, and to compare the pictures resulting from Δr and ΔMEP. Both approaches clearly show that the main changes in the electronic structure occur in the TS region. The ΔMEP picture is fully consistent with that based on Δρ for the reactions of the neutral species leading to the neutral products without large charge transfer between the fragments. In the case of reactions with large electron density displacements, the ΔMEP picture is dominated by charge transfer leading to more clear indication of charge shifts than the analysis of Δr. Methods: All the calculations were performed using the ADF package. The Becke–Perdew exchange–correlation functional was used with the Grimme's dispersion correction (D3 version) with Becke-Johnson damping. The Slater TZP basis sets defined within the ADF program were applied. For the analysed reactions, the stationary points were determined and verified by frequency calculations, and the IRC was determined. Further analysis was performed for the structures of reactants, TS, products, and the points corresponding to the minimum and maximum of the reaction force. For each point, two fragments, A and B, corresponding to the reactants were considered. The deformation density was calculated as the difference between the electron density of the system AB and the sum of densities of A and B, Δ ρ r = ρ AB r - ρ A r - ρ B r , with the same fragment definition as in the ETS-NOCV method. Correspondingly, deformation in MEP was determined as Δ V r = V AB r - V A r - V B r . [ABSTRACT FROM AUTHOR]

• Novel organoammonium-Cd(II) hybrid material synthesized and characterized. • Crystal structure elucidated via X-ray diffraction and Hirshfeld analysis. • Crystal morphology predicted using Bravais-Friedel-Donnay-Harker (BFDH) model. • Optical, electronic properties explored experimentally and theoretically. • Chemical reactivity assessed with conceptual-DFT calculations. This study reports the synthesis and characterization of an organoammonium-cadmium(II) hybrid material, (BPH₂)₂[Cd₂Cl₈] (BP = 1-butylpiperazine), using a combination of experimental and theoretical techniques. Single-crystal X-ray diffraction shows a centrosymmetric crystal structure in the P 1 ¯ space group, featuring a zero-dimensional (0D) arrangement where binuclear [Cd₂Cl₈]⁴⁻ anions and (C₈H₂₀N₂⁺) cations are linked by N—H···Cl and C—H···Cl hydrogen bonds. Hirshfeld surface analysis further elucidates these intermolecular noncovalent interactions, highlighting the dominant role of H···Cl contacts in the molecular packing. The crystal morphology is further investigated via the Bravais-Friedel-Donnay-Harker (BFDH) model. Infrared (IR) spectroscopic analysis was conducted to identify vibrational modes, confirm structure, and elucidate bonding features. Additionally, Experimental UV–visible study indicates an optical band gap energy of 4.75 eV, and density functional theory (DFT) calculations corroborate these findings, predicting a direct band gap of 4.45 eV. Moreover, theoretical calculations, including the complex dielectric function, band structure, and total density of states (DOS), were performed to explore the electrical and optical properties. Finally, the chemical reactivity was evaluated using conceptual-DFT descriptors at the B3LYP/SDD/aug-cc-pVTZ level of theory. [Display omitted] [ABSTRACT FROM AUTHOR]

• The rate-limiting step of sulfate reactions with alkanes at low temperatures is the oxidation of SO 4 2− to SO 3 2−. • The reaction pathway of TSR reaction between SO 4 2− and CH 4 at low temperatures is SO 4 2− → SO 3 2− → HSO 2 − → HSO− → HS− → H 2 S. • The oxidation order of sulfate in low temperature TSR reaction is HSO 4 − > [MgSO 4 ] CIP >SO 4 2−. • The sequence of alkanes participating in TSR reactions is n -C 5 H 12 > n -C 4 H 10 > C 3 H 8 > C 2 H 6 > CH 4. To reduce the energy consumption of heavy oil thermal recovery, low-temperature hot water flooding is becoming popular. The occurrence of thermochemical sulfate reduction (TSR) reactions during the hot water flooding process generates H 2 S, which can corrode equipment and jeopardize personnel safety. Preventing and managing H 2 S requires studying TSR reactions. The study investigated the reactivity of SO 4 2-, HSO 4 -, and [MgSO 4 ] CIP in the TSR reaction during heavy oil low-temperature hot water flooding. The results indicated that during low-temperature hot water flooding, no significant thermal cracking of heavy oil occurs, only a minor aquathermolysis takes place, while the TSR reaction proceeds vigorously. The TSR reaction leads to increased yields of H 2 S, CH 4 , and CO 2 , as well as a higher S content in the heavy oil. Based on experimental results, numerical simulations of the reaction process between SO 4 2- and CH 4 were conducted using density functional theory and transition state theory. The results indicated that the reduction of SO 4 2- to produce SO 3 2- is the rate-limiting step in the entire reaction pathway between SO 4 2- and CH 4. Further analysis of the reaction barriers and chemical reaction rates of the three sulfates (SO 4 2-, HSO 4 -, and [MgSO 4 ] CIP) and C1-C5 alkanes was conducted based on the limiting step. Through macro and micro analysis, this study not only confirmed previous findings regarding the order of alkanes participating in TSR reactions from the perspective of microscopic molecular but also clarified the oxidation order of sulfate species under heavy oil low-temperature thermal water flooding conditions, with the sequence being HSO 4 - > [MgSO 4 ] CIP >SO 4 2-. This study provides a foundational understanding of TSR reactions during heavy oil low-temperature hot water flooding and is of significance for the prediction and management of H 2 S. [ABSTRACT FROM AUTHOR]

The incorporation of supplementary cementitious materials (SCMs) in cement-based construction is fast becoming an environmentally friendly option to reduce CO 2 emissions associated with cement production. Fifteen raw materials i.e. two conventional (blast furnace slag and fly ash) and thirteen non-conventional (fayalite slag, glass wool, stone wool, ladle slag, municipal solid waste incineration bottom ash, waste glass, high silicate mine tailings, high magnesium mine tailings, high alumina mine tailings, volcanic pozzolan Iceland, calcined Finnish clay, stainless steel slags, and precast concrete sludge) available in the Nordics were investigated as SCMs. The reactivity of the materials was compared using R 3 test while the fresh and hardened properties of cementitious pastes with a 30% SCM replacement level were investigated via isothermal calorimetry, setting time, rheology, electrical resistivity, compressive strength, thermogravimetry and differential thermogravimetry (TG-DTG), x-ray diffraction (XRD), and scanning electron microscope coupled with energy-dispersive x-ray spectroscopy (SEM-EDS). The results showed that there exists a difference in the reactivities, and properties among the samples, attributed to the differences in the chemical and mineralogical composition of the SCM. Based on R 3 test, blast furnace slag, fly ash, ladle slag, glass wool, stone wool, volcanic pozzolan Iceland, and calcined Finnish clay are classified as reactive materials (higher heat release and bound water) while the remaining SCMs are classified as inert or slow reacting materials. Strong correlations were found between chemical reactivity and paste properties as paste samples containing reactive materials as SCM performed better, exhibiting a reduction in setting time while having higher reactivity, compressive strength, electrical resistivity, and denser microstructure than those containing inert or slow reacting materials. Moreover, sustainable performance index based on the relationship between the availability and reactivity criteria of SCMs was developed., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Priyadharshini Perumal reports financial support was provided by Interreg Northern Periphery and Arctic Project Ar2CorD. Adeolu Adediran reports financial support was provided by Auramo Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.)