Trying to contribute to an overall picture of solvation in ionic liquids, we report a review of the main recent results in the field of molecular dynamics simulations of structural and dynamic ...properties of mixtures of ionic liquids with molecular cosolvents or salts. The majority of reported results indicate that solvation of neutral molecules and salt ions takes place selectively in the bulk nanoregions of the dense ionic solvents, fitting the parts of the solute's moieties to the similar regions of the dense ionic solvent, in what has been called nanostructured solvation Méndez-Morales et al. J. Phys. Chem. B 118 (2014) 761–770.
On the example of 40 ion pairs (5 cations times 8 anions), this study demonstrates how the core‐level binding energy values can be calculated and used to plot theoretical spectra at low computational ...cost using density functional theory methods. Three approaches for obtaining the binding energy values are based on delta Kohn–Sham (ΔKS) calculations, 1s KS orbital energies, and atomic charges. The ΔKS results show reasonable agreement with the available experimental X‐ray photoelectron data. The 1s KS orbital energies correlate well with the ΔKS results. Atomic charge correlation with ΔKS is improved by accounting for the charges of neighboring atoms. Assignment of binding energies to atoms and the applicability of the mentioned methods to model systems of ionic liquids are discussed.
This study shows how the core‐level binding energy values can be calculated and used to plot theoretical spectra using three density functional theory‐based approaches: delta Kohn–Sham (ΔKS) calculations, 1s KS orbital energies, and atomic charges. Good agreement with the experimental X‐ray photoelectron data is established for the ΔKS results.
In this Letter, we report the first observation of the capacitance–potential hysteresis at the ionic liquid | electrode interface in atomistic molecular dynamics simulations. While modeling the ...differential capacitance dependence on the potential scan direction, we detected two long-living types of interfacial structure for the BMImPF6 ionic liquid at specific charge densities of the gold Au(111) surface. These structures differ in how counterions overscreen the surface charge. The high barrier for the transition from one structure to another slows down the interfacial restructuring process and leads to the marked capacitance–potential hysteresis.
The complex nature of electrode charge screening is well-known for ionic liquids (ILs). Due to strong ion–ion correlations, these electrolytes form a distinctive layered structure at interfaces. ...Variations in electrode potential cause structural changes that are reflected in a peculiar shape of differential capacitance–potential dependence with characteristic peaks. Although the differential capacitance for various ILs in conjunction with metal electrodes accessed via molecular dynamics (MD) simulations has been reported in the literature, retrieving a capacitance-potential curve, C(U), from the MD trajectories is not a trivial task. In this work, we present the results of the MD simulations of the IL 1-butyl-3-methylimidazolium hexafluorophosphate at a single-crystalline Au (100) surface. The discussion focuses on the simulation data treatment for C(U) curve fitting. It is shown that the resulting C strongly depends on the fitting method used. Four capacitance peaks and three structural reorganization types were identified in the studied system. With the help of a semi-quantitative approach in the framework of the original bilayer model of electric double layer (EDL), it is argued that the ions’ reorientation is in the origin of the capacitance peaks. Also, it is shown that under the conditions of this study, the multilayer structure, characteristic of EDL in ILs on the whole, is far from the “lattice saturation” regime. The multilayer structure possesses a steric packing effect that impedes structural changes, decreasing the capacitance.
Mixtures of alkylammonium-based protic ionic liquids and alkylmethylimidazolium-based aprotic ionic liquids near neutral and charged graphene interfaces were studied by means of molecular dynamics ...simulations. Effects previously observed for bulk mixtures were found to have a pronounced impact on the liquid's interfacial structure. Hydrogen bonding effects were found to affect the composition of the electric double layer (EDL). The lateral structure of the innermost layer of the EDL was found to be rich, showing transitions from solid-like to more fluid configurations, in which low mobility or high mobility anions give rise to hexagonal or striped patterns, respectively. Finally, two-dimensional nanoscale segregation, into polar/apolar domains but also into protic/aprotic domains, was seen at the graphene-liquid interface, resulting in a highly heterogeneous interfacial structure. The integral EDL capacitance vs. electrode potential was seen to nonlinearly increase with protic ionic liquid concentration due to the rearrangements of the three-dimensional ionic density distribution of species with different charge geometries close to the electrode.
Botanical supplements derived from grapes are functional in animal model systems for the amelioration of neurological conditions, including cognitive impairment. Rats fed with grape extracts ...accumulate 3′-O-methyl-quercetin-3-O-β-d-glucuronide (3) in their brains, suggesting 3 as a potential therapeutic agent. To develop methods for the synthesis of 3 and the related 4′-O-methyl-quercetin-7-O-β-d-glucuronide (4), 3-O-methyl-quercetin-3′-O-β-d-glucuronide (5), and 4′-O-methyl-quercetin-3′-O-β-d-glucuronide (6), which are not found in the brain, we have evaluated both enzymatic semisynthesis and full chemical synthetic approaches. Biocatalysis by mammalian UDP-glucuronosyltransferases generated multiple glucuronidated products from 4′-O-methylquercetin, and is not cost-effective. Chemical synthetic methods, on the other hand, provided good results; 3, 5, and 6 were obtained in six steps at 12, 18, and 30% overall yield, respectively, while 4 was synthesized in five steps at 34% overall yield. A mechanistic study on the unexpected regioselectivity observed in the quercetin glucuronide synthetic steps is also presented.
Botanical supplements derived from grapes are functional in animal model systems for the amelioration of neurological conditions, including cognitive impairment. Rats fed with grape extracts ...accumulate 3'-O-methyl-quercetin-3-O-β-Dglucuronide (3) in their brains, suggesting 3 as a potential therapeutic agent. To develop methods for the synthesis of 3 and the related 4'-O-methyl-quercetin-7-O-β-D-glucuronide (4), 3-O-methyl-quercetin-3'-O-β-D-glucuronide (5), and 4'-O-methylquercetin-3'-O-β-D-glucuronide (6), which are not found in the brain, we have evaluated both enzymatic semisynthesis and full chemical synthetic approaches. Biocatalysis by mammalian UDP-glucuronosyltransferases generated multiple glucuronidated products from 4'-O-methylquercetin, and is not cost-effective. Chemical synthetic methods, on the other hand, provided good results; 3, 5, and 6 were obtained in six steps at 12, 18, and 30% overall yield, respectively, while 4 was synthesized in five steps at 34% overall yield. Furthermore, a mechanistic study on the unexpected regioselectivity observed in the quercetin glucuronide synthetic steps is also presented.
Abstract
Background
The optimal treatment of anastomotic leak after rectal cancer resection is unclear. This worldwide cohort study aimed to provide an overview of four treatment strategies applied.
...Methods
Patients from 216 centres and 45 countries with anastomotic leak after rectal cancer resection between 2014 and 2018 were included. Treatment was categorized as salvage surgery, faecal diversion with passive or active (vacuum) drainage, and no primary/secondary faecal diversion. The primary outcome was 1-year stoma-free survival. In addition, passive and active drainage were compared using propensity score matching (2 : 1).
Results
Of 2470 evaluable patients, 388 (16.0 per cent) underwent salvage surgery, 1524 (62.0 per cent) passive drainage, 278 (11.0 per cent) active drainage, and 280 (11.0 per cent) had no faecal diversion. One-year stoma-free survival rates were 13.7, 48.3, 48.2, and 65.4 per cent respectively. Propensity score matching resulted in 556 patients with passive and 278 with active drainage. There was no statistically significant difference between these groups in 1-year stoma-free survival (OR 0.95, 95 per cent c.i. 0.66 to 1.33), with a risk difference of −1.1 (95 per cent c.i. −9.0 to 7.0) per cent. After active drainage, more patients required secondary salvage surgery (OR 2.32, 1.49 to 3.59), prolonged hospital admission (an additional 6 (95 per cent c.i. 2 to 10) days), and ICU admission (OR 1.41, 1.02 to 1.94). Mean duration of leak healing did not differ significantly (an additional 12 (−28 to 52) days).
Conclusion
Primary salvage surgery or omission of faecal diversion likely correspond to the most severe and least severe leaks respectively. In patients with diverted leaks, stoma-free survival did not differ statistically between passive and active drainage, although the increased risk of secondary salvage surgery and ICU admission suggests residual confounding.
The optimal treatment strategy for anastomotic leakage after restorative rectal cancer surgery remains unknown. This large, international collaborative study investigated various outcomes after four predefined treatment strategies for anastomotic leakage. Substantial differences were observed in patient and leakage characteristics, as well as outcomes following the four treatment strategies. However, no statistically significant differences were reported in stoma-free survival rates between active (vacuum) drainage and passive drainage.
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