Exchange Pathways Research Articles

Transcriptome reveals the toxicity difference of dimethyl disulfide by contact and fumigation on Meloidogyne incognita through calcium channel-mediated oxidative phosphorylation

The prevention and control of root-knot nematode disease has been posing a severe challenge worldwide. Fumigant dimethyl disulfide (DMDS) has excellent biological activity against nematodes. However, DMDS displays significant differences in contact and fumigation toxicity on nematodes. The specific regulatory mechanisms of DMDS on nematodes were investigated by characterizing the ultrastructure of nematodes, examining the physiological and biochemical indicators, and conducting transcriptome high-throughput sequencing. As indicated by the results, DMDS fumigation exhibited the biological activity of against M. incognita 121 times higher than DMDS contact. DMDS contact destroyed nematode body wall cells. Besides, DMDS fumigation destroyed the structure of pseudocoelom. DMDS treatment expedited the oxygen consumption of nematode while inhibiting acetylcholinesterase activity. As indicated by the analysis of vital signaling pathways based on transcriptome, DMDS based on the contact mode penetrated directly into the nematode through the body wall and subsequently affected calcium channels in the body wall and muscle, disrupting their structure; it serves as an uncoupling agent to interfere with ATP synthase. Moreover, DMDS based on the fumigation mode entered the body through the respiratory pathway of olfactory perception-oxygen exchange and subsequently affected calcium channels in the nerve; eventually, DMDS acted on complex IV or complex I.

Manipulating electron extraction efficiency in microbial electrochemical carbon fixation via single-atom engineering

Microbial electrochemical carbon fixation can directly convert CO2 to renewable fuels, holding the promise of reducing greenhouse gas emissions. Whereas its further development is largely shadowed by the unclear correlation between the coordination environment and carbon-fixation biohybrids. Here, we report a single-atom engineering approach to control extracellular and interspecies charge exchange pathways for high electron efficiency via synergistic effects of Co-N4 coordination and microbiome biohybrids in the electro-methanogenesis system. Optimized carbon-fixation microbial community structures composed of electroactive methanogens and boosted extracellular polymeric substance-mediated charge exchange achieved a 21.49 times methane production rate of 568.7 mmol/m2/day (up to a maximum value of 1014 mmol/m2/day at −1.0 V vs. Ag/AgCl) and a 4.76 times faradic efficiency of 90.1% at −0.9 V vs. Ag/AgCl compared to control groups. Density functional theory calculations indicate that high Co-N/Co-C incorporation promotes the conversion of redox electron carriers for CO2 reduction, and Co-N/Co-C reduced the energy barrier of conductive substances and facilitated the electron storage at the bio/abiotic interface. The synergistic effect between Co-N4 structure and microbiome biohybrids facilitates an effective electron transfer, serving as reliable guiding principles for other microbial electrochemical systems to synthesize sustainable and value-added products.

Exogenous spraying of IAA improved the efficiency of microspore embryogenesis in Wucai (Brassica campestris L.) by affecting the balance of endogenous hormones, energy metabolism, and cell wall degradation

BackgroundMicrospore embryogenesis is an extraordinarily complicated process, comprehensively regulated by a composite network of physiological and molecular factors, among which hormone is one of the most crucial factors. Auxin is required for stress-induced microspore reprogramming, however, the mechanism of its regulation of microspore embryogenesis is still unclear.ResultsIn this study, we found exogenously spraying 100 mg·L− 1 IAA on the buds of Wucai significantly increased the rate of microspore embryogenesis, and moreover accelerated the process of embryogenesis. Physiological and biochemical tests showed that the contents of amino acids, soluble total sugar, soluble protein, and starch were significantly increased after IAA treatment. Furthermore, exogenously spraying 100 mg·L− 1 IAA significantly enhanced IAA, GA4, and GA9 content, increased catalase (CAT) and malondialdehyde (MDA) activity, and reduced abscisic acid (ABA), MDA and soluble protopectin content, H2O2 and O2·− production rate in the bud with the largest population of late-uninucleate-stage microspores. Transcriptome sequencing was performed on buds respectively treated with 100 mg·L− 1 IAA and fresh water. A total of 2004 DEGs were identified, of which 79 were involved in micropores development, embryonic development and cell wall formation and modification, most of which were upregulated. KEGG and GO analysis revealed that 9.52% of DEGs were enriched in plant hormone synthesis and signal transduction pathways, pentose and glucuronic acid exchange pathways, and oxidative phosphorylation pathways.ConclusionsThese findings indicated that exogenous IAA altered the contents of endogenous hormone content, total soluble sugar, amino acid, starch, soluble protein, MDA and protopectin, the activities of CAT and peroxidase (POD), and the production rate of H2O2 and O2·−. Combined with transcriptome analysis, it was found that most genes related to gibberellin (GA) and Auxin (IAA) synthesis and signal transduction, pectin methylase (PME) and polygalacturonase (PGs) genes and genes related to ATP synthesis and electron transport chain were upregulated, and genes related to ABA synthesis and signal transduction were downregulated. These results indicated that exogenous IAA treatment could change the balance of endogenous hormones, accelerate cell wall degradation, promote ATP synthesis and nutrient accumulation, inhibit ROS accumulation, which ultimately promote microspore embryogenesis.

Upwelling impact and lateral transport of dissolved PAHs in the Taiwan Strait and adjacent South China Sea

The spatial distribution and depth profile of dissolved polycyclic aromatic hydrocarbons (PAHs) were investigated in the western Taiwan Strait (TWS) and northeastern South China Sea (SCS) during the southwest monsoon for a comprehensive study of spatial distribution, potential sources, upwelling, and lateral PAHs transport flux to assess the impacts of oceanic processes. The concentrations of ∑14PAHs were 33 ± 14 ng L−1 and 23 ± 11 ng L−1 in western TWS and northeastern SCS, respectively. A minor difference in potential sources in different areas was shown in principle component analysis results, which illustrated mixed sources (petrogenic and pyrogenic) in western TWS and petrogenic sources in northeastern SCS. An “enrichment in surface or deep but depletion in medium water” distribution pattern of PAHs depth profile during summertime was observed in Taiwan Bank, which was potentially influenced by the upwelling. The greatest lateral ∑14PAHs transport flux was found along the Taiwan Strait Current area (43.51 g s−1), followed by those along South China Sea Warm Current and Guangdong Coastal Current areas. Though the oceanic response to PAHs varied relatively slowly, the ocean current was a less-dominant pathway for PAHs exchange between the SCS and the East China Sea (ECS).

Spin Frustrated Pyrazolato Triangular CuII Complex: Structure and Magnetic Properties, an Overview

The synthesis and structural characterization of a new triangular Cu3–μ3OH pyrazolato complex of formula, [Cu3(μ3−OH)(pz)3(Hpz)3][BF4]2 (1−Cu3), Hpz = pyrazole, is presented. The triangular unit forms a quasi-isosceles triangle with Cu–Cu distances of 3.3739(9), 3.3571(9), and 3.370(1) Å. This complex is isostructural to the hexanuclear complex [Cu3(μ3−OH)(pz)3(Hpz)3](ClO4)2]2 (QOPJIP). A comparative structural analysis with other reported triangular Cu3–μ3OH pyrazolato complexes has been carried out, showing that, depending on the pyrazolato derivative, an auxiliary ligand or counter-anion can affect the nuclearity and/or the dimensionality of the system. The magnetic properties of 1−Cu3 are analyzed using experimental data and DFT calculation. A detailed analysis was performed on the magnetic properties, comparing experimental and theoretical data of other molecular triangular Cu3–μ3OH complexes, showing that the displacement of the μ3−OH− from the Cu3 plane, together with the type of organic ligands, influences the nature of the magnetic exchange interaction between the spin-carrier centers, since it affects the overlap of the magnetic orbitals involved in the exchange pathways. Finally, a detailed comparison of the magnetic properties of 1−Cu3 and QOPJIP was carried out, which allowed us to understand the differences in their magnetic properties.

Neurofluids and the glymphatic system: anatomy, physiology, and imaging.

First described in 2012, the glymphatic system is responsible for maintaining homeostasis within the central nervous system, including nutrient delivery, waste clearance, and consistency of the ionic microenvironment. It is comprised of glial cells and barrier systems that modulate neurofluid production, circulation, and exchange. Experimental interrogation of neurofluid dynamics is restricted to ex vivo and in vitro studies in animals and humans, therefore diagnostic imaging plays an important role in minimally invasive evaluation. This review article will synthesize current knowledge and theories regarding neurofluid circulation and implications for neuroimaging. First, we will discuss the anatomy of the neurogliovascular unit, including paravascular and perivascular pathways of fluid exchange. In addition, we will summarize the structure and function of barrier systems including the blood-brain, blood-cerebrospinal fluid, and brain-cerebrospinal fluid barriers. Next, we will mention physiologic factors that yield normal variations in neurofluid circulation, and how various disease pathologies can disrupt glymphatic drainage pathways. Lastly, we will cover the spectrum of diagnostic imaging and interventional techniques with relevance to glymphatic structure, flow, and function. We conclude by highlighting current barriers and future directions for translational imaging and applications to neurologic disorders.

Evidence for a novel cranial thermoregulatory pathway in thalattosuchian crocodylomorphs.

Thalattosuchian crocodylomorphs were a diverse clade that lived from the Early Jurassic to the Early Cretaceous. The subclade Metriorhynchoidea underwent a remarkable transition, evolving from semi-aquatic ambush predators into fully aquatic forms living in the open oceans. Thalattosuchians share a peculiar palatal morphology with semi-aquatic and aquatic fossil cetaceans: paired anteroposteriorly aligned grooves along the palatal surface of the bony secondary palate. In extant cetaceans, these grooves are continuous with the greater palatine artery foramina, arteries that supply their oral thermoregulatory structures. Herein, we investigate the origins of thalattosuchian palatal grooves by examining CT scans of six thalattosuchian species (one teleosauroid, two early-diverging metriorhynchoids and three metriorhynchids), and CT scans of eleven extant crocodylian species. All thalattosuchians had paired osseous canals, enclosed by the palatines, that connect the nasal cavity to the oral cavity. These osseous canals open into the oral cavity via foramina at the posterior terminus of the palatal grooves. Extant crocodylians lack both the external grooves and the internal canals. We posit that in thalattosuchians these novel palatal canals transmitted hypertrophied medial nasal vessels (artery and vein), creating a novel heat exchange pathway connecting the palatal vascular plexus to the endocranial region. Given the general hypertrophy of thalattosuchian cephalic vasculature, and their increased blood flow and volume, thalattosuchians would have required a more extensive suite of thermoregulatory pathways to maintain stable temperatures for their neurosensory tissues.

Thermochemically driven layer structure collapse via sulfate roasting toward the selective extraction of lithium and cobalt from spent LiCoO2 batteries

With the rapid development of new energy devices, a large amount of spent lithium-ion batteries (LIBs) are produced every year. Recovering valuable metals from spent LIBs is significant for achieving environmental protection and alleviating resource shortages. In this study, a novel approach by in situ thermal reduction technology with waste copperas is developed to recycle valuable metals from spent LiCoO2 (LCO) batteries. The mechanism study through in situ x-ray diffractometer and thermal analysis reveal that the sulfation of LCO underwent two pathways i.e., ion exchange and gas-solid reactions. In the ion exchange pathway, the layered structure of LCO collapse due to the reduction by divalent iron in copperas, and the detachment of lithium ions result in a larger lattice spacing of transition metal layer and formation of a stable spinel structure. Furthermore, the SO2 generated from the decomposition of iron sulfates reduces the unreacted LCO through gas-solid interactions, realizing the sulfation of lithium and cobalt completely. Economic analysis indicates the potential benefit of this process is approximately 8266$/t spent LCO. This study provides an alternative technological route and a new approach to green recovery of the spent LCO batteries, exhibiting great potential for wide applications.

Neutron scattering sum rules, symmetric exchanges, and helicoidal magnetism in MnSb2O6

MnSb$_{2}$O$_{6}$ is based on the noncentrosymmetric $P321$ space group with magnetic Mn$^{2+}$ ($S={5/2}$, $L\approx 0$) spins ordering below $T_{\mathrm{N}}=12$ K in a helicoidal structure. The ground state magnetic structure, expected to be built and originate from 7 Heisenberg exchange constants, has been shown to be coupled to the underlying crystallographic chirality with polar domain switching being reported. We apply neutron spectroscopy to extract these symmetric exchange constants. Given the high complexity of the magnetic exchange network, crystallographic structure and complications fitting linear spin-wave models, we take advantage of multiplexed neutron instrumentation to use the first moment sum rule of neutron scattering to estimate the 7 exchange constants. We then use these parameters to calculate the low-energy spin-waves in the N\'eel state to reproduce the neutron response without strong antisymmetric coupling. Using Green's response functions, the stability of long-wavelength excitations in the context of proposed magnetic structures is then discussed. The results show the presence of strong exchange constants for the chiral exchange pathways and illustrate an underlying coupling between crystallographic and magnetic ``chirality" through predominantely symmetric exchange.

BiMn7O12 : Polar antiferromagnetism by inverse exchange striction

Despite extensive research on magnetically induced ferroelectricity there exist relatively few studies on how a preexisting electric polarization affects magnetic order. Given that well-established magnetoelectric coupling schemes can in principle work in reverse, one might anticipate that primary, polar magnetic structures could be uniquely stabilized in ferroelectric crystals, however, this scenario is apparently rare. Here, we show that in ferroelectric $\mathrm{Bi}{\mathrm{Mn}}_{7}{\mathrm{O}}_{12}$, a pure, polar $E$-type antiferromagnetic order emerges below ${T}_{1}=59$ K, and we present a phenomenological model of trilinear magnetoelectric coupling consistent with ${\mathrm{Bi}}^{3+}$ lone-pair driven polar distortions uniquely stabilizing the polar antiferromagnetism via modulation of Heisenberg exchange pathways, i.e., inverse exchange striction. In addition, below ${T}_{2}=55$ K there occurs large commensurate canting of the $E$-type structure due to the onset of ferrimagnetic order on a separate crystallographic sublattice that may be exploited for additional magnetoelectric functionality.

Megafossils of Betulaceae from the Oligocene of Qaidam Basin and their paleoenvironmental and phytogeographic implications

Understanding the paleoenvironment and phytogeographical history of the Tibetan Plateau, China relies on discovering new plant fossils. The Qaidam Basin has long been regarded as an ideal ‘field laboratory’ to investigate the paleoclimate and paleobiological evolution of the northern Tibetan Plateau. However, fossil angiosperms from the Qaidam Basin are rare, and our knowledge of its paleovegetation is poor. Here, we report fossil leaves and fruits of Betulaceae found from the Oligocene Shangganchaigou Formation of northwestern Qaidam Basin (Huatugou area). Comparative morphological analysis led us to assign the fruits to the Betula subgenus Betula and the leaves to Carpinus grandis. These findings, together with other reported fossil plants from the same locality, reveal a close floristic linkage between the Qaidam Basin and Europe during the Oligocene. The northern pathway of this floristic exchange may have crossed through the Qaidam Basin during the late Paleogene. This floristic linkage may have been facilitated by the continuous narrowing of the Turgai Strait and stronger westerlies, which transported moisture and provided favorable climatic conditions. Indeed, fossil plants collected from the Qaidam Basin suggest that during the Oligocene this region had warm and humid deciduous broad-leaf forest, which differs from the region’s modern vegetation and indicates that the Qaidam Basin may have been a suitable region for these plants to flourish and spread during the Oligocene.

Effects of several superabsorbent polymers on soil exchangeable cations and crop growth

Owing to their excellent water absorption and water retention properties, superabsorbent polymers have become an important technology for realizing agricultural water savings. To explore the exchange pathways of exchangeable cations in soil caused by different superabsorbent polymers and their effects on crop nutrient uptake and growth, three types of superabsorbent polymers, sodium acrylate, potassium acrylate and acrylamide–sodium acrylate, were used in this project to study the effects of different dosages on crop growth, root morphology and the distributions of Na+, K+, Ca2＋ and Mg2+ in the root tips. The results were as follows: among all the treatments, the inhibition effect of the sodium acrylate superabsorbent polymer was the most obvious. Compared with CK, the biomass decreased by 70.3% (AN2), the root length and root surface area decreased by 62.7% and 61.1% respectively, plant K+ and Na+ increased by 18.5% and 2423% respectively, and Ca2+ and Mg2+ decreased by 27.6% and 18.7% respectively. Adsorption experiments with Ca2＋ and Mg2+ further proved that the superabsorbent polymers adsorbed more than 95% of the Ca2＋ and Mg2+ in the soil while releasing Na+ and K+ into the soil after swelling.

Luminescence Measurements of the Hyperthermal Reactions of N/N+ + NH3.

Chemiluminescence from a system of collisions, N+/N/Kr+/Kr/Xe+/Xe + NH3, at collision energies between 10 and 170 eV (center of mass, COM), was measured in the spectral range 300-1000 nm. The energy dependence of the emission excitation cross sections was quantified, and molecular signatures were fit to known spectroscopic constants to determine vibrational-state populations. For both N and N+ collision species, the strongest features were assigned to emissions from NH (A-X) and the atomic hydrogen Balmer series. For each of the spectra resulting from collisions with primary cations, the NH (A-X) emissions had the largest cross sections reaching values of (1.0-1.5) × 10-18 cm2 by 100 eV. Additional features originating from atomic nitrogen and NH (c-a) emissions were also observed. The NH (c-a) emissions accounted for about 8%, 13%, and 15% for total excited populations in collisions with Xe+, N+, and Kr+, respectively. These transitions were consistent with short-range interactions resulting in collision-induced dissociation of the NH3 molecule with apparent energy thresholds between 20 and 30 eV and emission cross sections decreasing with ion mass. Evidence of charge exchange in the N+ + NH3 collisions was observed in the resulting spectra as broad transitions between 420 and 480 nm and were assigned to NH+ emitting from the (B) state. Differences between the spectra were observed as changes in the emission signal with the neutral collisions producing only 30% or 65% of the NH (A-X) emission cross sections compared to the cation results for xenon and krypton, respectively. For N and N+, NH (A) was created in equal amounts at lower collision energies, but the emission for the neutral system increases above that of the cation at collision energies greater than 80 eV COM. In both cases, the threshold energy for appearance was below 10 eV, suggesting an additional pathway for NH (A) formation, namely, hydrogen abstraction or charge exchange and abstraction for the N and N+, respectively. In all cases, the neutral NH (c-a) emission intensity was similar between neutral and cation pairs. The H-α emission line (n = 3-2) decreased to about 10%, 33%, and 50% of the corresponding cation spectra for xenon, krypton, and nitrogen, respectively.

Ocean warming and acidification affect the transitional C:N:P ratio and macromolecular accumulation in the harmful raphidophyte Heterosigma akashiwo

Despite an increase in ocean warming and acidification that is expected to increase the number of harmful algal species worldwide, the population of the raphidophyte Heterosigma akashiwo has been reported to be reduced. However, how this species physically and metabolically modifies transitional C:N:P ratio and macromolecule accumulation is unknown. Considering 1st, 10th, and 20th culture generations under present (low-temperature; low-carbon-dioxide [LTLC] 21 °C; pCO2 400 ppm) and future (high-temperature; high-carbon-dioxide [HTHC] 25 °C; pCO2 1000 ppm) ocean conditions, we examined transitional C:N:P ratio and macromolecule level changes and performed transcriptome sequencing. The results showed that compared to 1st generation cells, 20th generation cells under HTHC conditions showed a large decrease in carbon quota (QC: 34%), nitrogen quota (QN: 36%), and phosphorus quota (QP: 32%), which were reflected in an overall reduction in DNA and RNA quantity. Decreased activation of photosynthetic, carbon fixation and lipid metabolic pathways coincided with changes in photosynthetic efficiency, carbon concentration, and lipid accumulation after long-term (20th generation) exposure to HTHC conditions. We observed that these variations in internal metabolic pathways were caused by external changes in temperature, which activated the (Ca+) signaling pathway, and external changes in pCO2, which altered proton exchange pathways. Our results suggest that H. akashiwo in a temperate environment will undergo profound changes in C:N:P ratio and macromolecular properties, leading to programmed cell death, in the future.

Climatology of Transport in the Strait of Belle Isle

AbstractThe Strait of Belle Isle (SBI) is an important pathway for water mass exchanges between the Labrador Shelf and the Gulf of St. Lawrence (GSL), particularly for transport toward the GSL. Seasonal and inter‐annual variability of transport in the SBI are examined using 15 years of moored acoustic Doppler current profiler data. Tidal currents are largely along strait and homogeneous with depth. Transports are toward the GSL on average, lowest (−1.0 ± 0.8 dSv) from April to July, and highest (−4.0 ± 1.1 dSv) from September to January. Averaged seasonal transports are usually within one standard deviation of previously published modeled values. The volume of winter Labrador Shelf water (LShW) entering the GSL is computed by transport integration and compares well with integrated volumes that meet LShW temperature‐salinity criteria during an annual March survey of the GSL. Integrating over the whole year showed that on average 649 ± 397 km3 enters the GSL after the March surveys are conducted, independently of the volume that has entered up to March; this addition represents on average about a third of the total volume. Annual volumes of LShW calculated from transport suggest that flow through the SBI accounts for 12%–18% of the GSL winter surface mixed layer. Cross‐strait current shear may affect transport integration values, but sea surface temperature data suggests this bias is limited to the summer. Corrections are empirically derived to account for cross‐strait shear in our transport calculation. The corrected time series suggests that the average transport may be flowing toward the Labrador Shelf in July (0.6 ± 1.0 CI [0.1 1.1] dSv).

TAGNet: Learning Configurable Context Pathways for Semantic Segmentation.

State-of-the-art semantic segmentation methods capture the relationship between pixels to facilitate contextual information exchange. Advanced methods utilize fixed pathways for context exchange, lacking the flexibility to harness the most relevant context for each pixel. In this paper, we present Configurable Context Pathways (CCPs), a novel model for establishing pathways for augmenting contextual information. In contrast to previous pathway models, CCPs are learned, leveraging configurable regions to form information flows between pairs of pixels. We propose TAGNet to adaptively configure the regions, which span over the entire image space, driven by the relationships between the remote pixels. Subsequently, the information flows along the pathways are updated gradually by the information provided by sequences of configurable regions, forming more powerful contextual information. We extensively evaluate the traveling, adaption, and gathering (TAG) stages of our network on the public benchmarks, demonstrating that all of the stages successfully improve the segmentation accuracy and help to surpass the state-of-the-art results. The code package is available at: https://github.com/dilincv/TAGNet.

Abstract 120: Tissue Kallikrein Attenuates Early Ischemic Edema Progression By Increasing The Glymphatic System Kinetics In Pmcao Mice

The glymphatic system (GS) is a perivascular fluid exchange pathway, that is crucial for maintaining brain homeostasis, and may contribute to ischemic edema. Tissue Kallikrein treatment provides cerebral infarction patients with vasodilatory activity, which may facilitate the kinetics in GS. We hypothesized that Tissue Kallikrein could attenuate early ischemic edema following blood interruption by altering the kinetics of the GS. In this study, we evaluated the effects of Tissue Kallikrein on mice acute ischemic edema in pMCAO mice. A fluorescent tracer was injected into the striatum of mice, and the proportion of area infused by the fluorescent tracer in the brain parenchyma was measured to assess the kinetics of the GS. The effect of Tissue Kallikrein on edema was determined by DWI/T2 mismatch, ischemic edema progression was indicated by a mismatch between diffusion-weighted imaging (DWI) and T2-weighted imaging (T2WI), that is, an acute ischemic lesion on DWI without a corresponding lesion on T2WI. Concurrently, correlation analysis was performed for the kinetics and the time windows of DWI/T2 mismatch. Our results indicated that Tissue Kallikrein attenuated brain edema was associated with improved GS kinetics in mice with pMCAO. In brief, this study shows the neuroprotective effects of Tissue Kallikrein in ischemic edema for the first time in pMCAO mice by boosting the GS kinetics.

Solid‐State Confinement Effects in Selective exo‐H/D Exchange in the Rhodium σ‐Norbornane Complex [(Cy2PCH2CH2PCy2)Rh(η2:η2‐C7H12)][BArF4

AbstractDensity functional theory calculations modelling selective exo‐H/D exchange observed in the Rh σ‐alkane complex [(Cy2PCH2CH2PCy2)Rh(η2:η2‐endo‐NBA)][BArF4], [1‐NBA][BArF4], are reported, where ArF=3,5‐C6H3(CF3)2 and NBA=norbornane, C7H12. Two models were considered 1) an isolated molecular cation, [1‐NBA]+ and 2) a full model in which [1‐NBA][BArF4] is treated in the solid state through periodic DFT. After an initial endo‐exo rearrangement, both models predict H/D exchange to proceed through D2 addition and oxidative cleavage followed by a rate‐limiting C−H activation of the norbornane through a σ‐CAM step to form a [1‐Rh(D)(η2‐HD)(norbornyl)]+ intermediate. HD rotation followed by a σ‐CAM C−D bond formation, HD reductive coupling and HD loss then complete the H/D exchange process. exo‐H/D exchange is facilitated by a supporting agostic interaction and is consistently more accessible kinetically than the potentially competing endo‐H/D exchange (isolated cation: ΔG≠exo=+15.9 kcal/mol, ΔG≠endo=+18.4 kcal/mol; solid state: ΔG≠exo=+22.1 kcal/mol, ΔG≠endo=+25.1 kcal/mol). The solid‐state environment has a significant impact on the computed energetics, with barriers increasing by ca. 7 kcal/mol, while only the solid‐state model correctly predicts the endo‐bound NBA complex to be the resting state of the system. These outcomes reflect solid‐state confinement effects within the pocket occupied by the [1‐NBA]+ cation and defined by the pseudo‐octahedral array of neighbouring [BArF4]− anions. The asymmetry of the solid‐state environment also requires a second H/D exchange pathway to be defined to account for reaction at all four exo‐C−H bonds. These entail slightly higher barriers (ΔG≠exo=+24.8 kcal/mol, ΔG≠endo=+27.5 kcal/mol) but retain a distinct preference for exo‐ over endo‐H/D exchange.

Understanding surface complexation of antimony on Mg(OH)2: Insights from first-principles molecular dynamics

Sorption processes at the mineral–water interface are of great importance in dominating the fate and availability of metalloid contaminants in natural environment. Aiming at a thorough understanding of the complexation of antimony (Sb) on metal hydroxide, we conducted first-principles molecular dynamic (FPMD) simulations and batch adsorption experiments to elucidate the quantitative mechanism of Sb complexation on Mg(OH)2. Batch experiments showed the sorption of Sb(III) is nearly pH-independent, while increasing pH markedly weakened Sb(V) sorption; the measured sorption isotherm curves were well fitted by Langmuir model. Subsequently, molecular-level mechanism of Sb(V)/Sb(III) on brucite basal and edge surfaces were revealed by FPMD, including microscopic surface reactive sites, local complexing structures and coordination geometries, and complexing free energies. Results showed that Sb(III)/Sb(V) can form outer-sphere complexation on basal surface by hydrogen bonding. On edge surface, Sb(III)/Sb(V) formed stable inner-sphere mononuclear monodentate and binuclear bidentate complexes. The calculated free energies indicated that the binuclear bidentate complexing was more favorable than monodentate structure, and the complexation of Sb(III) was more stable than Sb(V). Accordingly, reaction pathway of the ligand exchange and thermodynamic stability of the different inner-sphere complexes were clarified. This study provides theoretical basis for evaluating the environmental risk of Sb and improving the engineering efficiency of Sb-contaminated water management.

Multimetallic post-synthetic modifications of copper selenide nanoparticles.

In this report, we investigate the addition of two metal cations, simultaneously and sequentially to Cu2-xSe nanoparticles. The metal combinations (Ag-Au, Ag-Pt, Hg-Au and Hg-Pt) are chosen such that one metal adds to the structure via cation exchange and the other adds to the structure via metal deposition when added individually to Cu2-xSe nanoparticles. Surprisingly, we find that for each metal combination, across all three synthesis routes, cation exchange and metal deposition products are obtained without deviation from the outcomes seen in the binary metal systems. However, within those outcomes the data show several types of heterogeneities in the morphologies formed including extent and composition of cation exchange products as well as the extent and composition of the metal deposited products. Taken together, these results suggest a hierarchical control for nanoheterostructure morphologies where the pathways of cation exchange or metal deposition in post-synthetic modification of Cu2-xSe exhibit relatively general outcomes as a function of metal, regardless of synthetic approach or metal combination. However, the detailed composition and interface populations of the resulting materials are more sensitive to both metal identities and synthetic procedure (e.g. order of reagent addition), suggesting that certain principles of metal chalcogenide post-synthetic modification are excitingly robust, while also revealing new avenues for both mechanistic discovery and structural control.