Organic compounds are widespread pollutants in wastewater, causing significant risks for living organisms. In terms of advanced oxidation processes, photocatalysis is known as an effective technology ...for the oxidation and mineralization of numerous non-biodegradable organic contaminants. The underlying mechanisms of photocatalytic degradation can be explored through kinetic studies. In previous works, Langmuir-Hinshelwood and pseudo-first-order models were commonly applied to fit batch-mode experimental data, revealing critical kinetic parameters. However, the application or combination conditions of these models were inconsistent or ignored. This paper briefly reviews kinetic models and various factors influencing the kinetics of photocatalytic degradation. In this review, kinetic models are also systemized by a new approach to establish a general concept of a kinetic model for the photocatalytic degradation of organic compounds in an aqueous solution.
A new approach for kinetics study of photocatalytic degradation of organic compounds.
Low back pain, knee osteoarthritis, and cancer patients suffer from chronic pain. Aberrant nerve growth into intervertebral disc, knee, and tumors, are common pathologies that lead to these chronic ...pain conditions. Axonal dieback induced by capsaicin (Caps) denervation has been FDA-approved to treat painful neuropathies and knee osteoarthritis but with short-term efficacy and discomfort. Herein, we propose to evaluate pyridoxine (Pyr), vincristine sulfate (Vcr) and ionomycin (Imy) as axonal dieback compounds for denervation with potential to alleviate pain. Previous literature suggests Pyr, Vcr, and Imy can cause undesired axonal degeneration, but no previous work has evaluated axonal dieback and cytotoxicity on adult rat dorsal root ganglia (DRG) explants. Thus, we performed axonal dieback screening using adult rat DRG explants in vitro with Caps as a positive control and assessed cytotoxicity. Imy inhibited axonal outgrowth and slowed axonal dieback, while Pyr and Vcr at high concentrations produced significant reduction in axon length and robust axonal dieback within three days. DRGs treated with Caps, Vcr, or Imy had increased DRG cytotoxicity compared to matched controls, but overall cytotoxicity was minimal and at least 88% lower compared to lysed DRGs. Pyr did not lead to any DRG cytotoxicity. Further, neither Pyr nor Vcr triggered intervertebral disc cell death or affected cellular metabolic activity after three days of incubation in vitro. Overall, our findings suggest Pyr and Vcr are not toxic to DRGs and intervertebral disc cells, and there is potential for repurposing these compounds for axonal dieback compounds to cause local denervation and alleviate pain.
Hymexazol is a volatile fungicide widely used in agriculture, causing its abundance in the atmosphere; thus, its atmospheric fate and conversion are of great importance when assessing its ...environmental impacts. Herein, we report a theoretical kinetic mechanism for the oxidation of hymexazol by OH radicals, as well as the subsequent reactions of its main products with O2 and then with NO by using the Rice–Ramsperger–Kassel–Marcus-based Master equation kinetic model on the potential energy surface explored at the ROCBS-QB3//M06-2X/aug-cc-pVTZ level. The predicted total rate constants k total(T, P) for the reaction between hymexazol and OH radicals show excellent agreement with scarcely available experimental values (e.g., 3.6 × 10–12 vs (4.4 ± 0.8) × 10–12 cm3/molecule/s at T = 300 K and P = 760 Torr); thus, the calculated kinetic parameters can be confidently used for modeling/simulation of N-heterocycle-related applications under atmospheric and even combustion conditions. The model shows that 3,4-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-5-yl (IM2), 3,5-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-4-yl (IM3), and (3-hydroxy-1,2-oxazol-5-yl)methyl (P8) are the main primary intermediates, which form the main secondary species of (3,4-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-5-yl)dioxidanyl (IM4), (3,5-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-4-yl)dioxidanyl (IM7), and ((3-hydroxy-1,2-oxazol-5-yl)methyldioxidanyl (IM11), respectively, through the reactions with O2. The main secondary species then can react with NO to form the main tertiary species, namely, (3,4-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-5-yl)oxidanyl (P19), (3,5-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-4-yl)oxidanyl (P21), and (3-hydroxy-1,2-oxazol-5-yl)methyloxidanyl (P23), respectively, together with NO2. Besides, hymexazol could be a persistent organic pollutant in the troposphere due to its calculated half-life τ1/2 of 13.7–68.1 h, depending on the altitude.
The carbonyl-olefin metathesis (COM) reaction is a highly valuable chemical transformation in a broad range of applications. However, its scope is much less explored compared to analogous ...olefin-olefin metathesis reactions. Herein we demonstrate the use of tropylium ion as a new effective organic Lewis acid catalyst for both intramolecular and intermolecular COM and new ring-opening metathesis reactions. This represents a significant improvement in substrate scope from recently reported developments in this field.
Substituted pyrans and furans are core structures found in a wide variety of natural products and biologically active compounds. Herein, we report a practical and mild catalytic method for the ...synthesis of substituted pyrans and furans using molecular iodine, a simple and inexpensive catalyst. The method described is performed under solvent-free conditions at an ambient temperature and atmosphere, thus offering a facile and practical alternative to currently available reaction protocols. A combination of experimental studies and density functional theory calculations revealed interesting mechanistic insights into this seemingly simple reaction.
Monitoring water surface dynamics is essential for the management of lakes and reservoirs, especially those are intensively impacted by human exploitation and climatic variation. Although modern ...satellites have provided a superior solution over traditional methods in monitoring water surfaces, manually downloading and processing imagery associated with large study areas or long-time scales are time-consuming. The Google Earth Engine (GEE) platform provides a promising solution for this type of “big data” problems when it is combined with the automatic water extraction index (AWEI) to delineate multi-temporal water pixels from other forms of land use/land cover. The aim of this study is to assess the performance of a completely automatic water extraction framework by combining AWEI, GEE, and Landsat 8 OLI data over the period 2014–2018 in the case study of New Zealand. The overall accuracy (OA) of 0.85 proved the good performance of this combination. Therefore, the framework developed in this research can be used for lake and reservoir monitoring and assessment in the future. We also found that despite the temporal variability of climate during the period 2014–2018, the spatial areas of most of the lakes (3840) in the country remained the same at around 3742 km
2
. Image fusion or aerial photos can be employed to check the areal variation of the lakes at a finer scale.
Purpose
The purpose of this study was to inspect the interactions between an anti-breast cancer, TAM, with model of lipid membranes composed of either zwitterionic DPPC LUVs or anionic DPPG LUVs and ...how they depend on ionic strength and cholesterol.
Methods
The K
p
of TAM into DPPC and DPPG LUVs were determined at three different NaCl concentrations by second derivative UV-Vis spectrophotometry. The effect of cholesterol incorporated into these LUVs on TAM’s K
p
was also assessed. The ATR-FTIR measurements were carried out to verify structural changes within the acyl chain and head group regions of the liposomes upon TAM partitioning.
Results
Increasing salt concentration produced negligible impact on the partitioning of TAM into DPPC bilayer as its K
p
remained unaffected whilst induced outstanding reduction of TAM’s K
p
into DPPG liposomes. Furthermore, TAM was found to disorder the lipids’ acyl chains, which could result in an increase in the membrane fluidity, a necessary piece of information to refer to when prescribing TAM dosage for administration. Additionally, cholesterol showed astoundingly opposite contribution to the partitioning of TAM into the LUVs, as its K
p
value reduced in DPPC/Chol bilayer yet increased in DPPG/Chol liposomes.
Conclusion
Ionic strength and cholesterol play a noteworthy role in regulation of TAM partitioning into lipid membranes as they could obstruct or promote such action.
The carbonyl–olefin metathesis reaction could facilitate rapid functional group interconversion and allow construction of complicated organic structures. Herein, we demonstrate that elemental iodine, ...a very simple catalyst, can efficiently promote this chemical transformation under mild reaction conditions. Our mechanistic studies revealed intriguing aspects of the activation mode via molecular iodine and the iodonium ion that could change the previously established perception of catalyst and substrate design for the carbonyl–olefin metathesis reaction.
N-Heterocyclic olefins (NHOs), the alkylidene derivatives of N-heterocyclic carbenes (NHCs), have recently emerged as a new family of promising organocatalysts with strong nucleophilicity and ...Brønsted basicity. The development of a novel method is shown using NHOs as efficient promoters for the direct dehydrogenative silylation of alcohols or hydrosilylation of carbonyl compounds. Preliminary results of the first NHO-promoted asymmetric synthesis are also discussed.
Naphthalene, the most prevalent and smallest member of the Polycyclic Aromatic Hydrocarbons (PAHs) family, has garnered significant scientific attention for its harmful environmental impacts and ...those of its degradation products. In this work, we comprehensively recharacterized the gas-phase reaction of naphthalene with OH radicals in a wide range of conditions (T = 200–2000 K &P = 0.76–7600 Torr), covering both atmospheric and combustion chemistry. Within the Rice–Ramsperger–Kassel–Marcus (RRKM)-based master equation framework, the detailed kinetic model was constructed on the potential energy surface explored at the ROCBS-QB3//M06–2X/aug-cc-pVTZ level of theory. Our model not only helps to resolve the existing large discrepancy (up to ∼1000 times) among the previously reported rate constants but also reveals mechanistic insights, including time-resolved species profiles and product distribution, for naphthalene transformation. It is shown that although naphthalene cannot be considered a persistent organic compound (POP) due to its rapid reaction with OH radicals, its chemical conversion can generate harmful substances such as O3 and carcinogenic derivatives. Also, the detailed conversion of naphthalene in water was investigated for the first time, revealing that naphthalene and its important degradation products pose a significant danger to aquatic life as hazardous pollutants.
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