Preferred Pathway Research Articles

Orbital-Driven Insights into Enantioselective Hydrofunctionalization of Alkenes Catalyzed by Co-Salen Complexes: Study on Singlet and Triplet States.

The Co(salen) ([LCo(II)]) mediated hydrofunctionalization of alkenes is a highly significant method for forming enantioselective products. In this work, we conducted comprehensive computational investigations to gain insights of the reaction mechanism. The orbital analysis and intrinsic bond orbital analysis (IBO) were utilized to unravel the flow of electrons during the progress of the reaction. We explored various spin state surfaces to understand the possible pathways for the reaction. Initially, [LCo(II)] reacts with an oxidant tertbutyl peroxybenzoate, yielding [LCo(III)OC(O)Ph] and [LCo(III)OtBu]. Subsequently, [LCo(III)OC(O)Ph] reacts with silane to form cobalt hydride ([LCo(III)H]), with the triplet spin state surface being the preferred pathway, featuring an energy barrier of 14.2 kcal mol-1. IBO analysis across this step revealed that it involves the transfer of hydrogen as a hydride. Subsequently, the [LCo(III)H] complex in a triplet spin state undergoes a minimum energy crossing point (MECP) to transition into the singlet spin state, representing its most stable configuration. The [LCo(III)H] complex further reacts with styrene via hydrogen atom transfer on the singlet spin state surface, followed by oxidation and subsequent reaction with indole on the doublet spin surface to yield the hydrofunctionalized product. This work also explores potential enantioselective steps in the reaction.

Synthesis of spiro[oxindole-2,3′-pyrrolidine] derivatives via exo-selective 1,3-dipolar cycloaddition reaction, characterization and DFT investigation

A series of spiro[oxindole-2,3′-pyrrolidine] derivatives (4a-q) were successfully synthesized via an exo-selective 1,3-dipolar cycloaddition reaction between a stabilized azomethine ylide and various (E)-3-arylidene-1-methylpyrrolidine-2,5-diones. The structures and stereochemistry of the cycloadducts were elucidated through 1D and 2D NMR spectroscopic techniques. The preferred reaction pathway was corroborated by DFT calculations using the B3LYP functional with the 6–31 G (d, p) basis set. The results revealed that the cycloaddition reaction follows a normal electron demand mechanism, where the azomethine ylide acts as the nucleophile and the dipolarophile as the electrophile. The Fukui function analysis favors the regio 2, contradicting the experimental observations while, transition state theory aligns perfectly with the experimental results.

Oxygen vacancy and boron dual sites enable efficient oxygen activation for emerging contaminant degradation: Boosted exciton dissociation via built-in electric field modulation

Two-dimensional (2D) layered materials are promising photocatalysts for environmental remediation through O2 activation. However, the inherent robust excitonic effects from the confined-layer structure hinder the generation of highly oxidative free radicals from the preferred charge transfer pathway. Taking 2D BiOBr as a prototype, we implemented a superficial surface boronizing method to incorporate oxygen vacancy (OV)-boron (B) dual sites onto the surface. The OV-B dual sites disorder the surface atomic arrangement of BiOBr and induce strong built-in electric field (BEF). This effectively weakens exciton binding energy, boosts exciton dissociation into free charges, and facilities the transfer and separation of free charges, which collectively enables charge transfer to surpass excitonic effects as the dominant O2 activation pathway. Consequently, BiOBr with OV-B dual sites outperforms pristine and mono-OV modified BiOBr in both O2 activation and emerging contaminant degradation. This work offers insightful strategies for modulating 2D photocatalysts to optimize O2 activation towards efficient contaminant removal.

Efficient photocatalytic degradation of ciprofloxacin using floating α-NiMoO4/mpg-C3N4/EP under visible light

Conventional water treatment processes often fail to effectively remove antibacterial drugs, necessitating advanced strategies. This study presents the synthesis of novel floating, visible light-active α-NiMoO4/mpg-C3N4/EP composites for the removal of ciprofloxacin (CFX), a widely used quinolone antibiotic, from water. These composites are easily recoverable, highly stable, and demonstrate excellent reusability. The optimal photocatalyst, NC-101/EP (α-NiMoO4/mpg-C3N4 = 10:1), achieved 96.2 ± 1.1% degradation of CFX at 1.6 g L−1 within 80 min under visible light, significantly outperforming previous benchmarks. This high efficiency is attributed to the formation of interfacial junctions and a built-in electric field, which enhanced charge transfer and hydroxyl radical generation through an S-scheme mechanism. Fluorescence spectroscopy provided precise monitoring of CFX degradation without interference from coexisting intermediates. Density functional theory (DFT) calculations revealed that hydroxyl radicals initiated highly favorable and spontaneous oxidation of CFX, with a reaction rate constant of 6.04 × 109 M−1 s−1. The preferred oxidation pathway followed the sequence: HO-addition > H-abstraction > single electron transfer. Four degradation pathways were identified, with key intermediates confirmed by high-resolution mass spectrometry. The process also significantly reduced CFX toxicity, ensuring minimal environmental impact. These findings position NC-101/EP as a promising photocatalyst for large-scale water treatment applications targeting antibiotic contamination.

Comparison of the Efficiency of B-O and B-C Bond Formation Pathways in Borane-Catalyzed Carbene Transfer Reactions Using α-Diazocarbonyl Precursors: A Combined Density Functional Theory and Machine Learning Study.

Lewis acidic boranes, especially tris(pentafluorophenyl)borane [B(C6F5)3], have emerged as metal-free catalysts for carbene transfer reactions of α-diazocarbonyl compounds in a variety of functionalization reactions. The established mechanism for how borane facilitates carbene generation for these compounds in the scientific community is based on the formation of a B-O (C=O) intermediate (path O). Herein, we report an extensive DFT study that challenges the notion of a ubiquitous path O, revealing that B-C(=N=N) bond formation (path C) for certain diazocarbonyl substrates proves to be the preferred pathway. This study elucidates, through the introduction of 22 various substituents on each side of the α-diazocarbonyl backbone, how the electron-donating and -withdrawing properties of substituents influence the competition between these B-O and B-C pathways. To elucidate the impact of the electronic features of diazo substrates on the competition between the O and C pathways in the studied dataset, we employed a machine learning approach based on the Random Forest model. This analysis revealed that substrates with higher electron density on the diazo-attached carbon, lower electron density on the carbonyl carbon, and more stable HOMO orbitals tend to proceed via path C. Furthermore, this study not only demonstrates that borane efficiency in facilitating N2 release is greatly affected by the nature of substituents on both sides of the α-diazocarbonyl functionality but also shows that for some substrates, borane is incapable of catalyzing the release of molecular nitrogen.

Investigation of ruthenium loaded beta zeolite catalyst performance in vanillin hydrodeoxygenation yielding both monomeric and dimeric cycloalkanes

The valorization of lignin-derived bio-oil is studied extensively due to its promising contribution to sustainability. Among these studies, many have focused on the hydrodeoxygenation (HDO) of phenolic model compounds as it is a crucial process in obtaining valuable oxygen-free hydrocarbons. In this work, vanillin HDO was performed on various bifunctional ruthenium-based zeolite catalysts with different zeolite supports (Y, ZSM-5, and beta) in a batch reactor. Ru-loaded beta zeolite catalysts (Ru/Hβ) exhibited the highest HDO activity among them, and the formation of dimeric cycloalkanes of high value were also observed specifically when using the Ru/Hβ catalyst. Due to their benefits of direct use in blending of biofuel, factors promoting the dimerization of phenolic monomers were extensively examined through a series of experiments using a mix of phenolic model compounds as HDO reactants. Specific oxygen containing functional groups contributed to the aldol condensation of aromatic species, and the structure and kinetic diameter of the monomers had a profound effect on the ability to participate in dimerization. Additionally, the metal loading of the catalyst and reaction conditions such as temperature and hydrogen pressure were varied to observe each of their effects on the product distribution. The change in metal loading had a remarkable impact on the preferred reaction pathway and product selectivity, while a high temperature of 200 °C and hydrogen pressure of 50 bar was determined to be necessary to fully achieve HDO to cycloalkanes. Consequently, this study has provided useful information on the production of both monomeric and dimeric cycloalkanes and has contributed to the development of the bio-oil upgrading process.

Tunneling Mechanisms of Quinones in Photosynthetic Reaction Center–Light Harvesting 1 Supercomplexes

In photosynthesis, light energy is absorbed and transferred to the reaction center, ultimately leading to the reduction of quinone molecules through the electron transfer chain. The oxidation and reduction of quinones generate an electrochemical potential difference used for adenosine triphosphate synthesis. The trafficking of quinone/quinol molecules between electron transport components has been a long‐standing question. Here, an atomic‐level investigation into the molecular mechanism of quinol dissociation in the photosynthetic reaction center–light‐harvesting complex 1 (RC–LH1) supercomplexes from Rhodopseudomonas palustris, using classical molecular dynamics (MD) simulations combined with self‐random acceleration MD‐MD simulations and umbrella sampling methods, is conducted. Results reveal a significant increase in the mobility of quinone molecules upon reduction within RC–LH1, which is accompanied by conformational modifications in the local protein environment. Quinol molecules have a tendency to escape from RC–LH1 in a tail‐first mode, exhibiting channel selectivity, with distinct preferred dissociation pathways in the closed and open LH1 rings. Furthermore, comparative analysis of free energy profiles indicates that alternations in the protein environment accelerate the dissociation of quinol molecules through the open LH1 ring. In particular, aromatic amino acids form π‐stacking interactions with the quinol headgroup, resembling the key components in a conveyor belt system. This study provides insights into the molecular mechanisms that govern quinone/quinol exchange in bacterial photosynthesis and lays the framework for tuning electron flow and energy conversion to improve metabolic performance.

Quantum Chemical Characterization of Rotamerism in Thio-Michael Additions for Targeted Covalent Inhibitors.

Myotonic dystrophy type I (DM1) is the most common form of adult muscular dystrophy and is a severe condition with no treatment currently available. Recently, small-molecule ligands have been developed as targeted covalent inhibitors that have some selectivity for and covalently inhibit cyclin-dependent kinase 12 (CDK12). CDK12 is involved in the transcription of elongated RNA sections that results in the DM1 condition. The covalent bond is achieved after nucleophilic addition to a Michael acceptor warhead. Previous studies of the conformational preferences of thio-Michael additions have focused on characterizing the reaction profile based on the distance between the sulfur and β-carbon atoms. Rotamerism, however, has not been investigated extensively. Here, we use high-level quantum chemistry calculations, up to coupled cluster with single, double, and perturbative triple excitations [CCSD(T)], to characterize the nucleophilic addition of an archetypal nucleophile, methanethiolate, to various nitrogen-containing Michael acceptors which are representative of the small-molecule covalent inhibitors. By investigating the structural, energetic, and electronic properties of the resulting enolates, as well as their reaction profiles, we show that synclinal additions are generally energetically favored over other additions due to the greater magnitude of attractive noncovalent interactions permitted by the conformation. The calculated transition states associated with the addition process indicate that synclinal addition proceeds via lower energetic barriers than antiperiplanar addition and is the preferred reaction pathway.

Synthesis of dihydrocarvone over dendritic ZSM-5 Zeolite: A comprehensive study of experimental, kinetics, and computational insights

This study explores the isomerization of limonene-1,2-epoxide (LE) from kinetic and mechanistic viewpoints, using a dendritic ZSM-5 zeolite (d-ZSM-5) as a highly selective catalyst for the formation of dihydrocarvone (DHC) in the form of diastereoisomers (cis + trans). Ethyl acetate, a green solvent, was used at mild reaction temperatures (50–––70 °C). DHC, which can also be extracted from caraway oil, is widely used as an intermediate for epoxylactone production and as a constituent in flavors and perfumes. Kinetic modeling of LE isomerization was performed using a reaction network with eight parallel reactions and the corresponding rate equations, derived from the assumption of the rate-limiting surface reactions. The large standard errors in the statistical results of some kinetic parameters of the initial data fitting suggested that three of those reactions can be neglected to describe the kinetic model more accurately. This refinement resulted in standard errors in the kinetic parameters lower than ca. 11 %, confirming the statistical reliability of the modified kinetic model. Activation energies of 41.1 and 162 kJ/mol were estimated for the formation of cis-DHC and trans-DHC, respectively. Density Functional Theory (DFT) calculations revealed the preferred pathway for both cis and trans-LE conversion to DHC and carveol. The rate-determining step, carbocation formation (ΔEact = 234 kJ/mol), precedes near-instantaneous dihydrocarvone formation under the studied conditions.

Identifying biochemical changes in the kidney using proton nuclear magnetic resonance in an adenine diet chronic kidney disease mouse model.

This study aimed to investigate the metabolic changes in the kidneys in a murine adenine-diet model of chronic kidney disease (CKD). Kidney fibrosis is the common pathological manifestation across CKD aetiologies. Sustained inflammation and fibrosis cause changes in preferred energy metabolic pathways in the cells of the kidney. Kidney cortical tissue from mice receiving a control or adenine-supplemented diet for 8weeks (late inflammation and fibrosis) and 12 weeks (8weeks of treatment followed by 4weeks recovery) were analysed by 2D-correlated nuclear magnetic resonance spectroscopy and compared with histopathology and biomarkers of kidney damage. Tissue metabolite and lipid levels were assessed using the MestreNova software. Expression of genes related to inflammation, fibrosis, and metabolism were measured using quantitative polymerase chain reaction. Animals showed indicators of severely impaired kidney function at 8 and 12 weeks. Significantly increased fibrosis was present at 8weeks but not in the recovery group suggesting some reversal of fibrosis and amelioration of inflammation. At 8weeks, metabolites associated with glycolysis were increased, while lipid signatures were decreased. Genes involved in fatty acid oxidation were decreased at 8weeks but not 12 weeks while genes associated with glycolysis were significantly increased at 8weeks but not at 12 weeks. In this murine model of CKD, kidney fibrosis was associated with the accumulation of triglyceride and free lactate. There was an up-regulation of glycolytic enzymes and down-regulation of lipolytic enzymes. These metabolic changes reflect the energy demands associated with progressive kidney disease where there is a switch from fatty acid oxidation to that of glycolysis.

Photo-reductive decomposition of perfluorooctane sulfonate (PFOS) and its common alternatives by UV/VUV/sulfite process: Mechanism, kinetic modeling, and water matrix effects

The present study investigated the photo-reduction of perfluorooctane sulfonate (PFOS) and its alternatives, focusing on decomposition mechanisms, active species involvement, the influence of background water constituents, and kinetic model development. The decomposition and defluorination rates followed the order of PFOS > PFHxS > 6:2 FTSA > PFBS, with shorter chains and CH2 linkers enhancing the resistance of PFOS alternatives against the attack of hydrated electrons (eaq−). Two primary pathways were identified during the photodegradation of PFAS: (i) H/F exchange at CF bonds with the lowest bond dissociation energies (BDEs) and (ii) functional group cleavage followed by short-chain PFCAs formation, with OH playing a crucial role in transforming intermediates. Adding iodide and elevated temperatures demonstrated a synergistic effect on PFBS decomposition and defluorination, with high temperatures promoting functional group cleavage as the preferred defluorination pathway. The study examined the impact of background water constituents in different aqueous environments, from surface waters to wastewater streams and ion-exchange brine concentrates. Chloride exhibited a concentration-based dual impact on the UV/VUV/sulfite process: promotive effects at low dosages (1–10 mM) by acting as a secondary eaq− mediator, and adverse effects at high dosages (20–500 mM) due to the scavenging effect of generated chlorine radicals (Cl). High ionic strength adversely affected eaq− quantum efficiency. Additionally, bicarbonate and natural organic matter (NOM) had opposing effects on PFOS photo-reduction, primarily through eaq− scavenging and pH alteration. Kinetic modeling revealed reaction rate constants of the studied PFAS with eaq− ranging from 1.8 × 106 to 1.3 × 109 M−1 s−1, corroborating the concentration profiles of active species and highlighting the reductive nature of sulfite-mediated processes.

Computational Exploration on Coupling Formic Acid Production with Propylene Synthesis via Catalytic Transfer Hydrogenation: The Role of CO2 beyond Reverse Water Gas Shift Reaction.

CO2-assisted propane dehydrogenation (CO2-ODHP) is emerging as an alternative route to the direct dehydrogenation of propane. Previous studies on CO2-ODHP have shown that the role of CO2 is to shift the reaction equilibrium toward the product side by consuming the produced H2 molecules via reverse water gas shift (RWGS) reaction. Since the ultimate fate of CO2 is to get reduced, we herein propose another pathway of CO2 reduction in the realm of CO2-ODHP─CO2 hydrogenation to formic acid (FA). With the objective of investigating the feasibility of this process, we, for the first time, carry out a computational investigation on coupling propane dehydrogenation with CO2 hydrogenation using a Ti-alkoxide-functionalized UiO-67 metal-organic framework. Analysis using the distortion/interaction model confirms that CO2 hydrogenation to FA is a preferred pathway over the RWGS reaction and hence can be realized in practice. Our study also highlights the importance of intersystem crossing, which provides an opportunity to access nonground state potential energy surfaces while undergoing chemical transformations. Again, subsequent addition of water molecules has shown to ease product desorption by 41 kcal/mol. Our study, therefore, hints at an unexplored role of CO2 beyond the RWGS reaction in oxidative propane dehydrogenation.

Aging mechanisms and kinetics of bis(2,2 dinitropropyl) formal facilitated by transition state bifurcation and HONO catalysis

Serving as energetic plasticizer, revealing the aging mechanisms and kinetics of bis(2,2-dinitropropyl) formal is helpful to remove the safety hazards. Here, based on the DFT barrier of methylene-H abstraction by nitro group (HONO elimination) and the continuous reaction model, an experimentally comparable half-life of BDNPF is reported by transition state theory simulation. Rather than the HONO elimination-addition reactions, HONO bimolecular decompositions are preferred, where the energetically preferred pathway involves formation of N2O3, and generation of N2O4 and HNO catalyzed by HONO. Interestingly, newly reported transition state bifurcations lower the barriers and accelerate HONO decomposition, which also leads to the rate constant of generating HNO consistent with experiments. Moreover, HNO undertakes hydrogen transferred bimolecular pathway and HONO-catalyzed pathway to decompose into N2O and H2O. This work clarifies the degradation pathways and species, and is helpful to the deep understanding of the aging procedures of energetic materials.

Influence of Catalyst Surface Structure on the Electrochemical Hydrogenation of Cis,Cis-Muconic Acid

Adipic acid (AA) production from petroleum-based cyclohexane is one of the largest chemical processes in terms of annual volumetric turnover accounting for 3 million tons as of 2022. The current commercial approach to synthesize AA is through the oxidation of petroleum-derived cyclohexane using nitric acid. The release of N2O in stoichiometric amounts makes it one of the most significant greenhouse gas (GhG) emitting processes. The abundance of biomass in the Midwestern United States has driven significant research efforts to synthesize bio-derived and sustainable commodity products and lower the chemical industry’s carbon footprint.1 cis,cis-Muconic acid (ccMA), a biobased C6 diunsaturated diacid platform molecule can be transformed to commodity chemicals like caprolactam, adipic acid, and terephthalic acid, with AA being of particular interest for the synthesis of nylon 6,6.2 For the first time in literature, we demonstrate appreciable production of AA (conversion: 91%, selectivity: >95%) through electrochemical hydrogenation (ECH) of ccMA on PGM catalysts. Carbon-supported palladium (Pd/C) and platinum (Pt/C) selectively produced AA while bulk Pd and Pt yielded the monounsaturated trans-3-hexenedioic acid (t3HDA) intermediate and H2 under all tested conditions. Such an influence of surface structure on the electrochemistry of organics is not unprecedented. Koper et. al3 studied Pt single crystals for the electrochemical hydrogenation of acetone and showed how activity, selectivity, and extent of catalytic poisoning are highly sensitive to the Pt surface structure. Similarly, we used density functional calculations to elucidate the structure-sensitive nature of ccMA ECH and its intermediates by identifying thermodynamically preferred reaction pathways as a function of surface geometry (terrace vs steps). The energetics coupled with experimental observations suggest that the reduction of ccMA to t3HDA occurs through an outer sphere proton-coupled electron transfer mechanism, while the reduction of HDA to AA preferentially occurs on Pd and Pt (111), the most abundant facet in Pd/C and Pt/C. Our calculations also explain the exceptional performance of Pd/C compared to Pt/C by the weaker binding of Pd terrace sites compared to Pt. Overall, combining renewable electricity, in-situ hydrogen generation from water, and a biologically-produced intermediate enabled us to open a sustainable route for bio-adipic acid production. This allows us to further design and optimize the catalyst for the selective production of biobased AA.

Sociodemographic Differences in Perspectives on Postpartum Symptom Reporting.

The overall goal of this work is to create a patient-reported outcome (PRO) and decision support system to help postpartum patients determine when to seek care for concerning symptoms. In this case study, we assessed differences in perspectives for application design needs based on race, ethnicity, and preferred language. A sample of 446 participants who reported giving birth in the past 12 months was recruited from an existing survey panel. We sampled participants from four self-reported demographic groups: (1) English-speaking panel, Black/African American race, non-Hispanic ethnicity; (2) Spanish-speaking panel, Hispanic-ethnicity; (3) English-speaking panel, Hispanic ethnicity; (4) English-speaking panel, non-Black race, non-Hispanic ethnicity. Participants provided survey-based feedback regarding interest in using the application, comfort reporting symptoms, desired frequency of reporting, reporting tool features, and preferred outreach pathway for concerning symptoms. Fewer Black participants, compared with all other groups, stated that they had used an app for reporting symptoms (p = 0.02), were least interested in downloading the described application (p < 0.05), and found a feature for sharing warning sign information with friends and family least important (p < 0.01). Black and non-Hispanic Black participants also preferred reporting symptoms less frequently as compared with Hispanic participants (English and Spanish-speaking; all p < 0.05). Spanish-speaking Hispanic participants tended to prefer calling their professional regarding urgent warning signs, while Black and English-speaking Hispanic groups tended to express interest in using an online chat or patient portal (all p < 0.05) CONCLUSION: Different participant groups described distinct preferences for postpartum symptom reporting based on race, ethnicity, and preferred languages. Tools used to elicit PROs should consider how to be flexible for different preferences or tailored toward different groups.

Effect of local chemical order on monovacancy diffusion in CoNiCrFe high-entropy alloy

High-entropy alloys (HEAs) are promising materials for nuclear applications. Understanding the influence of local chemical order (LCO) on defect diffusion and evolution in these alloys is crucial for enhancing their resistance to radiation damage. In this study, we used molecular dynamics simulation to investigate the effect of LCO on monovacancy diffusion in CoNiCrFe HEA. Alongside the Warren-Cowley parameter, which quantifies the degree of local elemental ordering, we propose a new parameter to characterize the spatial scale of LCOs. Based on their degree, LCO structures have been classified as either chemical medium-range order (CMRO) or chemical short-range order (CSRO). Our study reveals a non-monotonic variation in vacancy diffusion coefficients, transitioning from random solid solution to CSRO and then to CMRO structures. Moreover, we observe a preference for vacancy diffusion in low-energy Fe, Co-rich regions, with their spatial distribution and spatial connectivity significantly influencing the vacancy diffusion. Due to the spatial scale of the inhomogeneity introduced by LCO, both global average diffusion parameters and single migration barriers cannot fully reflect the actual diffusion dynamics. Therefore, our study emphasizes the importance of understanding the preferred diffusion pathways and the associated energy landscapes to fully assess the defect diffusion dynamics in HEAs. This deeper investigation into localized diffusion behaviors influenced by LCO is crucial for evaluating and enhancing the radiation damage tolerance of HEAs.

Monchique alkaline magmatic intrusion (SW Iberia): Geophysical modeling and relationship with active seismicity and hydrothermalism

Monchique is a prominent 902 m topographic high in SW Iberia, which stands out in the general flat landscape of southern Portugal. It lies to the north of the Africa-Eurasia plate boundary, which locally accommodates a slow oblique convergence (∼5 mm/yr). Monchique comprises alkaline magmatic rocks of Late Cretaceous age, intruded in a post-rift context. It hosts the most active seismic cluster in mainland Portugal and important hydrothermal activity.This work investigates the relationship between the alkaline intrusion, local seismicity and hydrothermalism.We present magnetic and gravity modeling based on new drone-borne magnetic data and ground gravity data. New magnetic mapping of Monchique shows a ∼ 15 km long dipolar anomaly with 7–8 km wavelength and 2000 nT amplitude. 3D magnetic inversion models the main Monchique intrusion as a high-susceptibility body, 15 km long and 6 km wide, located below the Monchique mountain and extending 5–7 km depth. 2D forward modeling and geological interpretation further support the existence of ENE-WSW oriented dike-like gabbroic bodies that may extend deeper, around which syenite units have later emplaced.We relocate the seismicity using NonLinLoc and a 3D regional tomographic model, and find that earthquakes align along four main lineations that radiate outwards from the intrusion. We also find that most earthquakes cluster between 8 and 18 km depth, below the magmatic intrusion. The b-value at the core of the seismic cluster is higher than at the surrounding region, possibly related to the local hydrothermalism. We present five new focal mechanisms that are compatible with the regional stress field, supporting a regional tectonic control.The emplacement of the Monchique alkaline intrusion left fractures in the lithosphere that currently act as preferred pathways for fluids. In the context of the present-day stress field, the enhanced fracturing and fluid circulation facilitate the localization of small-magnitude earthquakes.

Persistence and pathway of glyphosate degradation in the coastal wetland soil of central Delaware

Glyphosate is a globally dominant herbicide. Here, we studied the degradation and microbial response to glyphosate application in a wetland soil in central Delaware for controlling invasive species (Phragmites australis). We applied a two-step solid-phase extraction method using molecularly imprinted polymers designed for the separation and enrichment of glyphosate and aminomethylphosphonic acid (AMPA) from soils before their analysis by ultra-high-performance liquid chromatography (UHPLC) and Q Exactive Orbitrap mass spectrometry methods. Our results showed that approximately 90 % of glyphosate degraded over 100 d after application, with AMPA being a minor (<10 %) product. Analysis of glyphosate-specific microbial genes to identify microbial response and function revealed that the expression of the phnJ gene, which codes C-P lyase enzyme, was consistently dominant over the gox gene, which codes glyphosate oxidoreductase enzyme, after glyphosate application. Both gene and concentration data independently suggested that C-P bond cleavage—which forms sarcosine or glycine—was the dominant degradation pathway. This is significant because AMPA, a more toxic product, is reported to be the preferred pathway of glyphosate degradation in other soil and natural environments. The degradation through a safer pathway is encouraging for minimizing the detrimental impacts of glyphosate on the environment.

Mechanism and kinetics of polycarbonate synthesized from isosorbide: Identification on the reactivity of terminal groups

AbstractChallenges in the mechanistic and kinetic study on the polymerization with multiple functional monomers hinder the scale‐up for the controllable reaction process. Herein, poly (isosorbide carbonate) synthesized from isosorbide (ISB) was employed to investigate the reaction behavior of functional monomers during polymerization. DFT calculations not only determined the energetically preferable pathways but also provided explanations for the significant differences between terminal groups at the molecular level. Subsequently, the characteristic absorption bands were detected from 1000 to 1100 cm−1 for hydroxyls on ISB, providing a quantitative measure for asymmetric hydroxyls. The reaction network indicated that the reactivity was dominated by the types of terminal groups instead of the chain length. Thereafter, a functional group model with six kinetic parameters was built, acting a crucial role in reaction control and reactor design. This method can be promoted to other functional monomers, conducing to the industrialization of high‐performance polymers.

Retention forestry as a climate solution: Assessing biomass, soil carbon and albedo impacts in a northern temperate coniferous forest

Forest management pathways for nature-based climate solutions, such as variable retention harvesting (VRH), have been gaining traction in recent years; however, their net biochemical and biophysical impacts remain unknown. Here, we use a combination of close-range and satellite remote sensing, eddy covariance technique, and ground-based biometric measurements to investigate forest thinning density and aggregation that maintain ecosystem nutrients, enhance tree growth and provide a negative feedback to the local climate in a northern temperate coniferous forest stand in Ontario, Canada. Our results showed that soil carbon (C) and nitrogen (N) in VRH plots were significantly lower (p < 0.05) for all VRH treatments compared to unharvested plots. On average, soil C was reduced by −0.64 ± 0.22 Δ% C and N by −0.023 ± 0.008 Δ% N in VRH plots. We also observed the largest loss of soil C and N in open areas of aggregate plots. Furthermore, the changes in albedo resulting from VRH treatment were equivalent to removing a large amount of C from the atmosphere, ranging from 1.3 ± 0.2 kg C yr−1 m−2 in aggregate 33 % crown retention plots to 3.4 ± 0.5 kg C yr−1 m−2 in dispersed 33 % crown retention plots. Our findings indicate that spatially dispersed VRH resulted in minimal loss of soil C and N and the highest understory growth and C uptake, while enhanced tree growth and local cooling through increased albedo were observed in dispersed VRH plots with the fewest residual trees. These findings suggest that using the harvested trees from VRH in a way that avoids releasing C into the atmosphere makes dispersed VRH the preferred forest management pathway for nature-based climate solutions.