Pressure-Dependent Kinetics of the Reaction between CH₃O₂ and OH: TRIOX Formation

Reaction of methyl peroxy radicals with hydroxyl radicals (1) was studied using pulsed laser photolysis coupled to transient UV–vis absorption spectroscopy at 296 K over the 1–100 bar pressure range (bath gas He): CH3O2 + OH → CH3O + HO2 (1a), CH3O2 + OH → CH2OO + H2O (1b), and CH3O2 + OH → CH3OOOH (TRIOX) (1d). Channel 1a is the dominant channel under ambient conditions, while the contribution of channel 1b is less than 5% at 1 bar and 296 K. Channel 1c is strongly pressure-dependent and becomes dominant at high pressures. The measured branching ratio of channel 1c is α1c = 0.87 ± 0.20 at 100 bar and 296 K. The chain termination channel 1c forming important product TRIOX is experimentally evaluated over an extended pressure range (1–100 bar) for the first time. The stabilization channel 1c might play a role at ambient pressures and low temperatures as well as high pressures at ambient and elevated temperatures

Air- and Water-Stable Gold-Coated Gadolinium Metal Nanocrystals

Gold-coated gadolinium nanocrystals, with an average diameter of 3.20 ± 0.35 nm, have been synthesized at ambient temperature by alkalide reduction. Whereas uncoated gadolinium nanoparticles react violently with air and water, the gold-coated gadolinium nanocrystals reported here show no reaction even upon long-term exposure. This is the first example of air- and water-stable lanthanide metal nanocrystals, which may allow for the development of magnetic and biomedical applications of gadolinium and other lanthanide metal and alloy nanocrystals

PIG890721 Supplemental Material2 - Supplemental material for Non-intrusive reduced-order modeling for fluid problems: A brief review

Supplemental material, PIG890721 Supplemental Material2 for Non-intrusive reduced-order modeling for fluid problems: A brief review by Jian Yu, Chao Yan and Mengwu Guo in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering</p

PIG890721 Supplemental Material1 - Supplemental material for Non-intrusive reduced-order modeling for fluid problems: A brief review

Supplemental material, PIG890721 Supplemental Material1 for Non-intrusive reduced-order modeling for fluid problems: A brief review by Jian Yu, Chao Yan and Mengwu Guo in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering</p

Table_1_Environmental pollution and economic growth: Evidence of SO2 emissions and GDP in China.pdf

This study explores the inherent linkage mechanism between environmental pollution and economic growth using a non-linear MS (M)–VAR (p) model. The results indicate that, first, the growth rates of China's gross domestic product (GDP) and SO2 emissions are in a state of significant inertia. Second, when the system was in a medium-growth regime, the growth rates of SO2 emissions and GDP had a positive correlation, characterized by lower probability and weaker durability. Third, when the system was in a high- or low-growth regime, their growth rates were negatively correlated, characterized by higher probability and stronger durability. Overall, economic growth increases environmental pollution emissions, which intensifies as well as inhibits economic growth. The correlation and sustainability of SO2 emissions and GDP are closely related to the regional status of the entire system. This study is helpful in analyzing the reasons for the nonlinear linkage mechanism between environmental pollution and economic growth.</p

Production of Hydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) from Bromophenols by Manganese Dioxide

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are of significant concern because of their enhanced toxicological effects compared to PBDEs. Research to date has attributed the origin of OH-PBDEs to biological metabolism of PBDEs and natural production in the environment. However, it is unclear how OH-PBDEs are formed naturally. In this study, we explored the formation of OH-PBDEs via the oxidative transformation of simple bromophenols (BPs, e.g., 4-BP, 2,4-DBP, and 2,4,6-TBP) by birnessite (δ-MnO₂). Results showed that OH-PBDEs were readily produced by δ-MnO₂ with BPs as precursors. For example, oxidation of 2,4-DBP by δ-MnO₂ yielded 2′-OH-BDE-68 and 2′,5′-OH-BDE-25. Other OH-PBDEs, such as 6-OH-BDE-13, 2′,5′-OH-BDE-3, 4′-OH-BDE-121, and 2′,5′-OH-BDE-69, were detected from the reaction with 4-BP and 2,4,6-TBP. The formation of OH-PBDEs likely resulted from the oxidative coupling of bromophenoxy radicals. Mild acidic conditions enhanced while coexisting cations (e.g., Na⁺, Mg²⁺, and Ca²⁺) suppressed the transformation. Given the ubiquity of BPs and δ-MnO₂, oxidation of BPs by δ-MnO₂ and other metal oxides is likely an abiotic route for the formation of OH-PBDEs in the environment

Effect of Hydrophobic Moieties on the Assembly of Silica Particles into Colloidal Crystals

To boost the implementation of colloidal crystals (CCs) in separation science, the effects of the most common chromatographic reversed phases, that is, butyl and octadecyl, on the assembly of silica particles into CCs and on the optical properties of CCs are investigated. Interestingly, particle surface modification can cause phase separation during sedimentation because the assembly is highly sensitive to minute changes in surface characteristics. Solvent-induced surface charge generation through acid–base interactions of acidic residual silanol groups with the solvent is enough to promote colloidal crystallization of modified silica particles. In addition, solvation forces at small interparticle distances are also involved in colloidal assembly. The characterization of CCs formed during sedimentation or via evaporative assembly revealed that C4 particles can form CCs more easily than C18 particles because of their low hydrophobicity; the latter can only form CCs in tetrahydrofuran when C18 chains with a high bonding density have extra hydroxyl side groups. These groups can only be hydrolyzed from trifunctional octadecyl silane but not from a monofunctional one. Moreover, after evaporative assembly, CCs formed from particles with different surface moieties exhibit different lattice spacings because their surface hydrophobicity and chemical heterogeneity can modulate interparticle interactions during the two main stages of assembly: the wet stage of crystal growth and the late stage of nano dewetting (evaporation of interparticle solvent bridges). Finally, short, alkyl-modified CCs were effectively assembled inside silica capillaries with a 100 μm inner diameter, laying the foundation for future chromatographic separation using capillary columns

From Stereochemically Tunable Homopolymers to Stereomultiblock Copolymers: Lewis Base Regulates Stereochemistry in the Coordination Polymerization of 2‑Vinylpyridine

Excellent isoselectivity (mmmm > 99%) and high activity (TOF > 4000 h–1) were achieved for the first time in the polymerization of the polar 2-vinylpyridine by using the simple lutetium-based catalysts, Lu­(CH2SiMe3)3(THF)x(Py)2–x (x = 0, 1, 2). The isoselectivity (mm) of the polymer could be varied between 37% and 99% through simply altering the quantity of Lewis base (tetrahydrofuran, 1,4-diazabicyclo[2.2.2]­octane, 3-bromopyridine, and pyridine) added. Moreover, a novel method for preparing isotactic–atactic stereomultiblock poly­(2-vinylpyridine)­s was developed by the addition and removal of THF during polymerization. The polymerization process including stereoselective control mechanism was deduced by DFT calculations

Kinetics of the Reaction of CH₃O₂ Radicals with OH Studied over the 292–526 K Temperature Range

Reaction of methyl peroxy radicals with hydroxyl radicals, CH₃O₂ + OH → CH₃O + HO₂ (1a) and CH₃O₂ + OH → CH₂OO + H₂O (1b) was studied using pulsed laser photolysis coupled to transient UV–vis absorption spectroscopy over the 292–526 K temperature range and pressure 1 bar (bath gas He). Hydroxyl radicals were generated in the reaction of electronically excited oxygen atoms O­(¹D), produced in the photolysis of N₂O at 193.3 nm, with H₂O. Methyl peroxy radicals were generated in the reaction of methyl radicals, CH₃, produced in the photolysis of acetone at 193.3 nm, and subsequent reaction of CH₃ with O₂. Temporal profiles of OH were monitored via transient absorption of light from a DC discharge H₂O/Ar low-pressure resonance lamp at ca. 308 nm. The absolute intensity of the photolysis light was determined by accurate in situ actinometry based on the ozone formation in the presence of molecular oxygen. The overall rate constant of the reaction is <i>k</i>_1a+1b = (8.4 ± 1.7) × 10^–11(<i>T</i>/298 K)^−0.81 cm³ molecule^–1 s^–1 (292–526 K). The branching ratio of channel 1b at 298 K is less than 5%

From Stereochemically Tunable Homopolymers to Stereomultiblock Copolymers: Lewis Base Regulates Stereochemistry in the Coordination Polymerization of 2‑Vinylpyridine

Excellent isoselectivity (<i>mmmm</i> > 99%) and high activity (TOF > 4000 h^–1) were achieved for the first time in the polymerization of the polar 2-vinylpyridine by using the simple lutetium-based catalysts, Lu­(CH₂SiMe₃)₃(THF)_<i>x</i>(Py)_2–<i>x</i> (<i>x</i> = 0, 1, 2). The isoselectivity (<i>mm</i>) of the polymer could be varied between 37% and 99% through simply altering the quantity of Lewis base (tetrahydrofuran, 1,4-diazabicyclo[2.2.2]­octane, 3-bromopyridine, and pyridine) added. Moreover, a novel method for preparing isotactic–atactic stereomultiblock poly­(2-vinylpyridine)­s was developed by the addition and removal of THF during polymerization. The polymerization process including stereoselective control mechanism was deduced by DFT calculations