The role of errors related to DFT methods in calculations involving ion pairs of ionic liquids.

Ionic liquids (ILs) play a key role in many chemical applications. As regards the theoretical approach, ILs show added difficulties in calculations due to the composition of the ion pair and to the fact that they are liquids. Although density functional theory (DFT) can treat this kind of systems to predict physico-chemical properties, common versions of these methods fail to perform accurate predictions of geometries, interaction energies, dipole moments, and other properties related to the molecular structure. In these cases, dispersion and self-interaction error (SIE) corrections need to be introduced to improve DFT calculations involving ILs. We show that the inclusion of dispersion is needed to obtain good geometries and accurate interaction energies. SIE needs to be corrected to describe the charges and dipoles in the ion pair correctly. The use of range-separated functionals allows us to obtain interaction energies close to the CCSD(T) level. © 2017 Wiley Periodicals, Inc.

Understanding the Structure and Properties of Cholinium Amino Acid Based Ionic Liquids.

The molecular structure of novel ionic liquids based on cholinium amino acids (ChAA-ILs) has been analyzed. The polarization charge density for all ion pairs has been examined as a function of the hydrophobicity of the anion. The COnductor-like Screening MOdel σ-profiles and σ-potentials have been obtained and used to interpret the chemical behavior of ChAA-ILs. Some physicochemical properties such as density and viscosity have been estimated using the COnductor-like Screening MOdel for Realistic Solvation method. Furthermore, the effects of polarization on the molecular structure, physicochemical properties, and hydrophobicities have been evaluated. Finally, the results obtained have been compared with experimental data.

On the chemical behavior of C60 hosting H2O and other isoelectronic neutral molecules.

The density functional theory (DFT) was used to investigate the chemical behavior of C60 hosting neutral guest molecules (NGM). The deformed atoms in molecules (DAM) allowed identifying the regions of electron density depletion and accumulation. The studied NGM are CH4, NH3, H2O, and HF. Based on dipole moment and polarizabilities analyses it is predicted that the NGM@C60 should be more soluble in polar solvents than C60. The deformations on the surface electron density of the fullerenes explain this finding, which might be relevant for further applications of these systems. It was found that the intrinsic reactivity of studied NGM@C60 is only moderately higher than that of C60. This trend is supported by the global reactivity indexes and the frontier orbitals analyses. The free radical scavenging activity of the studied systems, via single electron transfer, was found to be strongly dependent on the chemical nature of the reacting free radical. The presence of the studied NGM inside the C60 influences only to some extent the reactivity of C60 toward free radicals. The distortion of the electron density on the C60 cage, caused by the NGM, is directly related to the electron withdrawing capacity of the later.

Electron density analysis of 1-butyl-3-methylimidazolium chloride ionic liquid.

An analysis of the electron density of different conformers of the 1-butyl-3-methylimidazolium chloride (bmimCl) ionic liquid by using DFT through the BVP86 density functional has been obtained within the framework of Bader's atom in molecules (AIM), localized orbital locator (LOL), natural bond orbital (NBO), and deformed atoms in molecules (DAM). We also present an analysis of the reduced density gradients that deliver the non-covalent interaction regions and allow to understand the nature of intermolecular interactions. The most polar conformer can be characterized as ionic by AIM, LOL, and DAM methods while the most stable and the least polar shows shared-type interactions. The NBO method allows to comprehend what causes the stabilization of the most stable conformer based on analysis of the second-order perturbative energy and the charge transferred among the natural orbitals involved in the interaction.

Accuracy of urea breath test performed immediately after emergency endoscopy in peptic ulcer bleeding.

AIMS: The aim of this work is to investigate the accuracy of the urea breath test (UBT) performed immediately after emergency endoscopy in peptic ulcer bleeding (PUB). METHODS: Urea breath test was carried out right after emergency endoscopy in patients with PUB. The accuracy of this early UBT was compared to a delayed one after hospital discharge that was considered the gold standard. Clinical and epidemiological factors were analyzed in order to study their influence on the accuracy of the early UBT. RESULTS: Early UBT was collected without any complication and good acceptance from all the 74 patients included. In 53 of the patients (71.6%), a delayed UBT was obtained. Comparing concordance between the two tests we have calculated an accuracy of 83% for the early UBT. Sensibility and specificity were 86.36 and 66%, respectively, with a positive predictive value of 92.68% and negative predictive value of 50% (Kappa index = 0.468; p = 0.0005; CI: 95%). We found no influence of epidemiological factors, clinical presentation, drugs, times to gastroscopy, Forrest classification, endoscopic therapy, hemoglobin, and urea levels over the accuracy of early UBT. CONCLUSIONS: Urea breath test carried out right after emergency endoscopy in PUB is an effective, safe, and easy-to-perform procedure. The accuracy of the test is not modified by clinical or epidemiological factors, ulcer stage, or by the type of therapy applied. However, we have found a low negative predictive value for early UBT, so a delayed test is mandatory for all negative cases.

Selective serotonin reuptake inhibitors and gastrointestinal bleeding: a case-control study.

BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs) have been associated with upper gastrointestinal (GI) bleeding. Given their worldwide use, even small risks account for a large number of cases. This study has been conducted with carefully collected information to further investigate the relationship between SSRIs and upper GI bleeding. METHODS: We conducted a case-control study in hospitals in Spain and in Italy. Cases were patients aged ≥18 years with a primary diagnosis of acute upper GI bleeding diagnosed by endoscopy; three controls were matched by sex, age, date of admission (within 3 months) and hospital among patients who were admitted for elective surgery for non-painful disorders. Exposures to SSRIs, other antidepressants and other drugs were defined as any use of these drugs in the 7 days before the day on which upper gastrointestinal bleeding started (index day). RESULTS: 581 cases of upper GI bleeding and 1358 controls were considered eligible for the study; no differences in age or sex distribution were observed between cases and controls after matching. Overall, 4.0% of the cases and 3.3% of controls used an SSRI antidepressant in the week before the index day. No significant risk of upper GI bleeding was encountered for SSRI antidepressants (adjusted odds ratio, 1.06, 95% CI, 0.57-1.96) or for whichever other grouping of antidepressants. CONCLUSIONS: The results of this case-control study showed no significant increase in upper GI bleeding with SSRIs and provide good evidence that the magnitude of any increase in risk is not greater than 2.

Effects of a high-fiber diet on symptoms of irritable bowel syndrome: a randomized clinical trial.

OBJECTIVE: We investigated the effects of dietary fiber on symptoms of irritable bowel syndrome. METHODS: A single-blind randomized clinical trial was designed. Fifty-six subjects with irritable bowel syndrome were prospectively and randomly assigned to one of two groups: group 1 received a diet containing 10.4 g/d of fiber and group 2 received a diet containing 30.5 g/d of fiber. Patients' body weights, nutritional intakes as assessed with 3-d written food records, and symptom scores were assessed at baseline and at 3 mo. RESULTS: There were no dropouts during the study. Total energy intake and the distribution of macronutrients were not significantly different between groups. Total dietary fiber intake did not reach recommended levels in either group but was higher in group 2 than in group 1 (25.95 +/- 2.12 g/d versus 6.06 +/- 2.7 g/d, P < 0.05). Initial fiber intake did not differ significantly between groups. Pain scores, bowel scores, and general scores improved in both groups (from baseline to 3 mo), and no significant differences were detected between groups. CONCLUSIONS: A modest fiber intake in patients with irritable bowel syndrome relieved symptoms, but this therapeutic benefit of fiber may have been due to a placebo effect because the results were similar in the low-fiber group.

Effect of soluble fiber intake in lipid and glucose levels in healthy subjects: a randomized clinical trial.

OBJECTIVE: The aim of our work was to carry out a randomized clinical trial with two diets, one enriched in fiber (total fiber 30 g and soluble fiber 4 g) to investigate the effect on lipid and glucose levels in healthy subjects. RESEARCH DESIGN AND METHODS: Fifty-three subjects were prospectively randomized to two groups (see Table 1). Group I received a diet with 10.4 g of fiber given as 1.97 g soluble fiber (pectins, gums and mucilages) and 8.13 g of insoluble fiber (hemicelullose, cellulose and lignins) and Group II received a diet with 30.5 g of fiber of which 4.11 g were soluble fiber and 25.08 g insoluble fiber. Prospective serial assessment of weight and nutritional intake (3 days written food records) were made. These determinations were performed at baseline and at 3 months. All enrolled subjects underwent the following examinations; fasting blood samples were drawn for measurement of total cholesterol, triglyceride concentrations and other lipid fractions, low density lipoprotein (LDL-cholesterol), high density lipoprotein (HDL-cholesterol), glucose, and insulin. RESULTS: Total calorie and fat consumption were lower than recommended in both groups (calories; group I 1633+/-417 kcal per day versus group II 1707.5 +/- 579 kcal per day:ns) and (fats; group I 73.4 +/- 22.7 g per day versus group II [72.6 +/- 28 g per day:ns), without differences in fatty acid intake profile. Total fiber intake did not reach that recommended in both diets but it was higher in group II ( 9.06 +/- 2.7 g per day versus 25.95 +/- 7.12 g per day: P < 0.05). Soluble fiber intake did not reach that recommended in both diets but it was higher in group II (1.7 +/- 0.58 g per day versus 3.5 +/- 0.96 g per day: P < 0.05). Body weight did not change in both groups during treatment. During treatment, in group II a significant change was detected from baseline in LDL-cholesterol and fasting glucose levels. LDL-cholesterol decreased by 12.8% (P < 0.05) and glucose decreased by 12.3% (P < 0.05). No statistical differences were detected among triglycerides, HDL-cholesterol, and insulin levels. CONCLUSIONS: Modest increases in soluble fiber intake in healthy subjects improved LDL cholesterol and glucose levels.