Pesticides are chemical compounds widely used to combat pests in crops, and they thus play a key role in agricultural production. However, due to their persistence in aquatic environments, even at ...low concentrations, their use has been considered an environmental problem and caused concern regarding the adverse effects on human health. This paper reports, for the first time, the mechanisms, kinetics, and an evaluation of the toxicity of picloram degradation initiated by OH radicals in the aqueous environment using quantum chemistry and computational toxicology calculations. The rate constants are calculated using a combination of formulations derived from the Transition State Theory in a realistic temperature range (250–310 K). The results indicate that the two favorable pathways (R1 and R5) of OH -based reactions occur by addition to the pyridine ring. The calculated rate constant at 298 K is compared with the overall second-order reaction rate constant, quantified herein experimentally via the competition kinetics method and data available in the literature showing an excellent agreement. The toxicity assessment and a photolysis study provide important information: i) picloram and the majority of degradation products are estimated as harmful; however, ii) these compounds can suffer photolysis in sunlight. The results of the present study can help understand the mechanism of picloram, also providing important clues regarding risk assessment in aquatic environments as well as novel experimental information.
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•Rate constants were estimated by experimental and theoretical approaches.•Topological analyses and Fukui functions were calculated.•Toxicity assessment was performed using the ECOSAR computational package.•The photolysis study was performed by TD-DFT.
Abstract
The degradation reaction of CH
2
CN radical with O(
3
P) was firstly studied using quantum chemical methods. The energetics were calculated at CCSD(T)/cc‐pVTZ//B3LYP/6‐311++G(d,p). The ...formation of the intermediate C‐IM1 (CH
2
C(O)N) is the dominant channel by addition between O(
3
P) and the central‐C atom of CH
2
CN. Due to higher barriers, the terminal‐C‐addition/elimination, N‐addition/elimination, substitution and hydrogen abstraction channels are negligible. The rate constants were calculated by means of the RRKM‐TST theory. The total rate constants revealed positive temperature dependence and pressure independence. The calculated results were in good agreement with the experimental values.
A continuous pilot-scale A2O reactor with a two-zone sedimentation tank (A2O-TST) was constructed for the formation of aerobic granular sludge (AGS) to treat real municipal sewage. The ...characteristics of sludge, nutrient removal performance and the corresponding microbial ecology dynamics were studied during granulation process. Experimental results indicated that AGS with a mean particle size of 210 μm and sludge volume index after 30 min of 47.5 mL/g was successfully formed with effluent COD, total nitrogen and total phosphorus concentrations in the reactor reaching 22.8, 3.5 and 0.2 mg/L, respectively. Furthermore, high throughput data indicated that granules in settling tank-1 (ST-1) harbored slow-growing autotrophic organisms like Nitrosomonas and Nitrospira, while the flocs in settling tank-2 (ST-2) were dominated by fast-growing heterotrophic organisms including Ca. Accumulibacter, Dechloromonas, Flavobacterium, Arcobacter and Halomonas. Simulation results using computational fluid dynamics and discrete element method (CFD-DEM) modeling verified that the selection pressure created by the TST separator contributed to the retention of heavy granules (>1.011 kg/m3 density) in ST-1 zone and the withdrawal of light flocs (<1.011 kg/m3 density) from ST-2 zone. Therefore, the segregation of biomass using the TST system provides an opportunity to select for desired microbial populations and to optimize the nitrogen and phosphorus removal performance of the A2O-TST reactor. This study could add a guiding sight into the application of two-sludge system based on AGS technology for upgrading traditional A2O process.
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•AGS is formed successfully in pilot-scale A2O reactor with two-zone settling tank.•A satisfactory effluent COD, TN, TP content of 22.8, 3.5 and 0.2 mg/L was achieved.•Biomass segregation by TST optimized the N and P removal capacity in the reactor.•CFD-DEM modeling showed that density and size are critical for biomass segregation.•A two-sludge system based on AGS gives a feasible plan for upgrading A2O process.
La gestión de las temperaturas, crucial en el contexto de cambio climático, ha centrado la atención de las políticas urbanas, relegando a un segundo plano los espacios periurbanos, como los campus ...universitarios. A través de la teledetección y del análisis estadístico, el artículo examina los efectos de los usos del suelo y las políticas medioambientales en el comportamiento espacial de las temperaturas superficiales en el campus de la Universitat Autònoma de Barcelona entre 2014 y 2022. Se identifica una relación directa entre usos del suelo urbanizados y desnudos con anomalías térmicas superiores a la media, mientras que las zonas cubiertas de vegetación natural están relacionadas con temperaturas superficiales inferiores a la media, señalando áreas críticas no consideradas por la agenda medioambiental universitaria. Este artículo propone estrategias de mitigación con el fin de mejorar las políticas medioambientales y aumentar el confort térmico de la comunidad universitaria.
The reactions of pyrazine, pyridazine, and pyrimidine with hydroxyl radicals are theoretically studied. The barrier heights obtained with different electronic structure methods indicate that the ...reactions can competitively proceed via either ion of a hydrogen atom by an OH radical or OH addition to carbon sites. However, the rate constants computed within the temperature range 200 to 1500 K suggest that tunneling play a role resulting in large branching ratios in favor of hydrogen ion channels at lower temperatures.
Due to the complex and highly heterogeneous land cover in urban areas, the single-temporal pixel-wise and parcel-wise classification cannot realize high-precision recognition of ground objects. ...Semantic segmentation of satellite image time series (SITS), can distinguish objects with similar spectral reflection and temporal evolution. However, optical SITS have problems of uneven time-frequency distribution and incomplete, which makes it impossible to directly use existing models to carry out time-series semantic segmentation. This study proposes a semantic segmentation network that combines optical and radar SITS, named multisource temporal attention (TA) fusion-based temporal-spatial transformer (MTAF-TST), to achieve high-precision land cover classification in urban areas. First, MTAF-TST uses the transformer spatial semantic segmentation module to extract the spatial context information of ground objects to realize pixel-level land cover classification, which relieves the salt-and-pepper phenomenon that is easy to occur in traditional pixel-by-pixel classification in complex scenes. Second, MTAF-TST uses the transformer time feature extraction module to mine long-range time-dependent and high-level semantic information, overcoming the drawbacks of traditional convolutional and recurrent neural networks that cannot mine long-range time-dependent features of SITS. Finally, MTAF-TST uses a multisource TA fusion module to fuse the depth features of optical and radar SITS, which overcomes the shortcomings of traditional direct feature stitching methods that cannot make full use of time-correlated features, achieving high-precision land cover classification. The experimental results show that the MTAF-TST can realize the complementarity of radar and optical SITS in terms of timing integrity, color, and texture, and effectively improve the accuracy of SITS classification.
The ultimate goal in cancer therapy and diagnosis is to achieve highly specific targeting to cancer cells. Coated with the source cancer cell membrane specifically derived from the homologous tumors, ...the nanoparticles are identified with the self-recognition internalization by the source cancer cell lines in vitro and the highly tumor-selective targeting “homing” to the homologous tumor in vivo even in the competition of another heterologous tumor. As the result, MNP@DOX@CCCM nanovehicle showed strong potency for tumor treatment in vivo and the MR imaging. This bioinspired strategy shows great potential for precise therapy/diagnosis of various tumors merely by adjusting the cell membrane source accordingly on the nanoparticle surface.
This work reveals the role of hydrogen in the N2 desorption using DFT calculations at the B3LYP/6-31G(d) level of theory as implemented in Gaussian 16 programme. The addition of one hydrogen on the ...active site, exothermicity by ≈380 kJ/mol, favors the hydrogenation of nearby active sites (ΔE ≈ 480 kJ/mol) but inhibits the hydrogenation of itself (ΔE ≈ 220 kJ/mol). N1 exposure with the highest barrier of 232.0 kJ/mol is the rate-determining step. By paying attention to this step, the potential roles are clarified: (1) two hydrogen attached to the same site creating a highly hydrogenated environment retards the overall reaction; (2) the attachment of one hydrogen to C2 site inhibits the overall reaction; and (3) the addition of one hydrogen on C1 and C3 sites favors the overall reaction. The proposed mechanism will help to explain various reported findings on the gasification of the carbonaceous surface.
•The hydrogenation of the armchair surface is studied by DFT modeling.•The overall N2 formation from the clean armchair surface is determined.•The role of hydrogen addition on the energetics of N2 formation is investigated.
BACKGROUNDAn estimated one fourth of the world's population is infected with Mycobacterium tuberculosis, and 5-10% of those infected develop tuberculosis in their lifetime. Preventing tuberculosis is ...one of the most underutilized but essential components of curtailing the tuberculosis epidemic. Moreover, current evidence illustrates that tuberculosis manifestations occur along a dynamic spectrum from infection to disease rather than a binary state as historically conceptualized. Elucidating determinants of transition between these states is crucial to decreasing the tuberculosis burden and reaching the END-TB Strategy goals as defined by the WHO. Vaccination, detection of infection, and provision of preventive treatment are key elements of tuberculosis prevention.OBJECTIVESThis review provides a comprehensive summary of recent evidence and state-of-the-art updates on advancements to prevent tuberculosis in various settings and high-risk populations.SOURCESWe identified relevant studies in the literature and synthesized the findings to provide an overview of the current state of tuberculosis prevention strategies and latest research developments.CONTENTWe present the current knowledge and recommendations regarding tuberculosis prevention, with a focus on M. bovis Bacille-Calmette-Guérin vaccination and novel vaccine candidates, tests for latent infection with M. tuberculosis, regimens available for tuberculosis preventive treatment and recommendations in low- and high-burden settings.IMPLICATIONSEffective tuberculosis prevention worldwide requires a multipronged approach that addresses social determinants, and improves access to tuberculosis detection and to new short tuberculosis preventive treatment regimens. Robust collaboration and innovative research are needed to reduce the global burden of tuberculosis and develop new detection tools, vaccines, and preventive treatments that serve all populations and ages.
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•Unimolecular mechanisms of DMM combustion were studied using DFT and CBS-QB3 methods.•Rate constants of complex (R1–R4) and simple bond fission (R5–R11) were calculated.•Results show ...comparable rates using TST and the RRKM theories for different reactions.•Pressure and temperature dependence on reaction mechanisms were investigated.•Branching ratio analysis shows domination of P5 with competition from P6/P7 channels.
Many recent studies have been considered dimethoxymethane (DMM) as a potent fuel additive which reduces soot production and nitrogen oxides (NOx) emissions of diesel and biodiesel fuel. This study reports thermo-kinetic investigation of DMM pyrolysis in temperature range 300–2000 K using M06-2X and ωB97XD density functional methods and modest cost ab initio/complete basis set-quadratic Becke3 (CBS-QB3) procedure. The energy profile has been constructed using possible unimolecular H-atom transfer reactions (R1–R4) and simple bond fission reactions (R5–R11). Rate constant calculations were conducted at high-pressure (HP) limit and in the fall-off regimes using classical transition state (TST) and the statistical Rice-Ramsperger-Kassel-Marcus (RRKM) theories, respectively. Based on CBS-QB3 energies, branching ratios analysis reveals unimportance of all H-atom transfer reactions at T ≥ 400 K, while the homolytic bond cleavage reaction R5 which produces CH3 and gauche– OCH2OCH3 fragments is considered the main dominated decomposition channel with high competition from R6 (CH3 and trans– CH3OCH2O) and R7 (CH3O and CH2OCH3) channels especially at elevated temperature.
