Computational Study of Copper(II) Complexation and Hydrolysis in Aqueous Solutions Using Mixed Cluster/Continuum Models

We use density functional theory (B3LYP) and the COSMO continuum solvent model to characterize the structure and stability of the hydrated Cu(II) complexes [Cu(MeNH_2)(H_2O)_(n−1)]^(2+) and [Cu(OH)_x(H_2O)_(n−x)]^(2−x) (x = 1−3) as a function of metal coordination number (4−6) and cluster size (n = 4−8, 18). The small clusters with n = 4−8 are found to be the most stable in the nearly square-planar four-coordinate configuration, except for [Cu(OH)_3(H_2O)]^−, which is three-coordinate. In the presence of the two full hydration shells (n = 18), however, the five-coordinate square-pyramidal geometry is the most favorable for Cu(MeNH_2)^(2+) (5, 6) and Cu(OH)^+ (5, 4, 6), and the four-coordinate geometry is the most stable for Cu(OH)_2 (4, 5) and Cu(OH)_3^− (4). (Other possible coordination numbers for these complexes in the aqueous phase are shown in parentheses.) A small energetic difference between these structures (0.23−2.65 kcal/mol) suggests that complexes with different coordination numbers may coexist in solution. Using two full hydration shells around the Cu^(2+) ion (18 ligands) gives Gibbs free energies of aqueous reactions that are in excellent agreement with experiment. The mean unsigned error is 0.7 kcal/mol for the three consecutive hydrolysis steps of Cu^(2+) and the complexation of Cu^(2+) with methylamine. Conversely, calculations for the complexes with only one coordination shell (four equatorial ligands) lead to a mean unsigned error that is >6.0 kcal/mol. Thus, the explicit treatment of the first and the second shells is critical for the accurate prediction of structural and thermodynamic properties of Cu(II) species in aqueous solution

Influence of the Fiscal System on Income Distribution in Regions and Small Areas: Microsimulated CGE Model for Côte d'Ivoire

The objective of this paper is to examine how a small open economy such as Côte d’Ivoire (CI) can obtain growth-based internal tax resources, and how the tax system affects households and individuals through relative prices. A microsimulated CGE model is used to analyse the effects of an alternative tax system on households by utilizing a survey. It is postulated that the military and political crisis that started in 1999 with the first coup d’etat in Côte d’Ivoire is transitory and that CI has an internal tax policy capacity. This paper indicates that an alternative tax structure can reduce distortion in regional poverty, inequality for households, and in cities and small areas of the country. A model is formulated using Côte d’Ivoire’s 1998-based social accounting matrix and the 1998 population survey of 4,200 households. The main findings of this study are that the post-crisis tax policies envisioned by the government (reducing the tax rate on firms, reducing import taxes and increasing taxes on household income) result in an increase in poverty and inequality at the regional, city and small area levels.

PAMAM Dendrimers Undergo pH Responsive Conformational Changes without Swelling

Atomistic molecular dynamics (MD) simulations of a G4-NH2 PAMAM dendrimer were carried out in aqueous solution using explicit water molecules and counterions (with the Dreiding III force field optimized using quantum mechanics). Our simulations predict that the radius of gyration (R_g) of the dendrimer changes little with pH from 21.1 Å at pH 10 (uncharged PAMAM) to 22.1 Å at pH 5 (charged with 126 protons), which agrees quantitatively with recent small angle neutron scattering (SANS) experiments (from 21.4 Å at pH 10 to 21.5 Å at pH 5). Even so we predict a dramatic change in the conformation. The ion pairing in the low pH form leads to a locally compact dense shell with an internal surface area only 37% of the high pH form with a dense core. This transformation from “dense core” at high pH to “dense shell” at low pH could facilitate the encapsulation and release of guest molecules (e.g., drugs) using pH as the trigger, making dendrimers a unique drug delivery vehicle

Evaluation of B3LYP, X3LYP, and M06-class density functionals for predicting the binding energies of neutral, protonated, and deprotonated water clusters

In this paper we assess the accuracy of the B3LYP, X3LYP, and newly developed M06-L, M06-2X, and M06 functionals to predict the binding energies of neutral and charged water clusters including (H_2O)_n, n = 2−8, 20), H_3O+(H_2O_)n, n = 1−6, and OH−(H_2O)_n, n = 1−6. We also compare the predicted energies of two ion hydration and neutralization reactions on the basis of the calculated binding energies. In all cases, we use as benchmarks calculated binding energies of water clusters extrapolated to the complete basis set limit of the second-order Møller−Plesset perturbation theory with the effects of higher order correlation estimated at the coupled-cluster theory with single, double, and perturbative triple excitations in the aug-cc-pVDZ basis set. We rank the accuracy of the functionals on the basis of the mean unsigned error (MUE) between calculated benchmark and density functional theory energies. The corresponding MUE (kcal/mol) for each functional is listed in parentheses. We find that M06-L (0.73) and M06 (0.84) give the most accurate binding energies using very extended basis sets such as aug-cc-pV5Z. For more affordable basis sets, the best methods for predicting the binding energies of water clusters are M06-L/aug-cc-pVTZ (1.24), B3LYP/6-311++G(2d,2p) (1.29), and M06/aug-cc-PVTZ (1.33). M06-L/aug-cc-pVTZ also gives more accurate energies for the neutralization reactions (1.38), whereas B3LYP/6-311++G(2d,2p) gives more accurate energies for the ion hydration reactions (1.69)

Post-operative maternal morbidity and mortality after caesarean delivery and laparotomy for uterine rupture at the gynecology and obstetrics service of the Ignace Deen National Hospital in Guinea

Background: The aim of the work was to study post-operative maternal morbidity and mortality after caesarean delivery and laparotomy for uterine failure, to describe the main causes and to analyze the risk factors.Methods: It was a descriptive, comparative and analytical study lasting 2 years with data collection in 2 phases, one of which was a retrospective study lasting one year from July 2018 to June 2019 and the other a prospective study also lasting one year, from July 2019 to June 2020. It concerned all pregnant women who had been caesarized or had had a laparotomy for uterine rupture with complications and those who had not developed any complications. The parameters studied were types of complications, risk factors and maternal mortality. The Chi-square test was used to compare the two populations with a significance level p=0.05.Results: During the study period, 6141 hospitalizations were recorded among which 5682 surgical procedures were performed, i.e. 92.52% of hospitalizations. Caesarean delivery accounted for 90.55% of surgical procedures and laparotomy for uterine rupture for 1.10%. The overall maternal post-operative morbidity rate was 7.60%. Post-operative anemia was by far the most common complication (75.76%) followed by infection (23.46%). The maternal death rate was 0.92% with a ratio of 409.97 maternal deaths per 100,000 live births and more than 2/3 of these deaths were due to caesarean delivery. Anemia and septic shock were the main causes of death. Factors related to this post-operative maternal morbidity were: age greater than or equal to 40 years, multi-parity, illiteracy, emergency obstetric evacuation, low socio-economic level, poor quality of prenatal follow-up and rupture of membranes before admission.Conclusion: In the emergency context concerning majority of our cesarean deliveries and the totality of uterine ruptures predispose the mother to high significant morbidity and mortality