Machine Learning-Boosted Design of Ionic Liquids for CO2 Absorption and Experimental Verification.

Efficient CO2 capture is indispensable for achieving a carbon-neutral society while maintaining a high quality of life. Since the discovery that ionic liquids (ILs; room-temperature molten salts) can absorb CO2, various solvents composed of molecular ions have been studied. However, it is challenging to observe the properties of each isolated ion component to control the function of ILs as they are mixtures of ions. Finding the optimal cation-anion combination for the CO2 absorbent from their enormous chemical space had been impossible in a practical sense. This study applied electronic structure informatics to explore ILs with high CO2 solubility from 402,114 IL candidates. The feature variables were determined by a set of cheap quantum chemistry calculations for isolated small-ion fragments, and the importance of molecular geometries and electronic states governing molecular interactions was identified via the wrapper method. As a result, it was clearly shown that the electronic states of ionic species must have essential roles in the CO2 physisorption capacity of ILs. Considering synthetic easiness for the candidates narrowed by the machine learning model, trihexyl(tetradecyl)phosphonium perfluorooctanesulfonate was synthesized. Using a magnetic suspension balance, it was experimentally confirmed that this IL has higher CO2 solubility than trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide, which is the previous best IL for CO2 absorption.

Clinicopathological study and management of liver abscess in a tertiary care center.

BACKGROUND: Liver abscess is a burning problem in tropical nations, with often lethal consequences and diagnostic/therapeutic challenges. We have determined etiopathology, clinical, radiological, and bacteriological characteristics of this condition and review its management strategies. MATERIALS AND METHODS: During the period of the month from May 2007 to September 2009, a prospective study was performed involving 125 patients admitted to the in-patient ward of the Department of General Surgery of N.R.S Medical College their diagnosis was made on the basis of clinical features (such as right upper abdomen pain, and fever), laboratory investigations and radiological evidence of liver abscess. RESULTS: Amoebic liver abscess was the most common (88%) type of liver abscess among the study groups. There was a strong correlation with the occurrence of liver abscesses and addiction to alcohol, history of diabetes mellitus and low socioeconomic status. The most common etiology of pyogenic liver abscess was Escherichia coli. Ultrasonography (USG) of the abdomen was accurate and cost-effective in diagnosis of liver abscesses. Percutaneous catheter drainage was the most effective method of treatment (with a 100% success rate). CONCLUSION: Most patients in our study had liver abscess of amoebic origin and had temporal relationship with diabetes, alcoholism, and staggering socioeconomic status. We suggest early recognition of clinical features and prompt abdominal USG as cost-effective means for treatment initiation and reducing complications.

Mechanical bowel preparation versus no preparation before colorectal surgery: A randomized prospective trial in a tertiary care institute.

BACKGROUND: In the first half of 20(th) century; mortality from colorectal surgery often exceeded 20%, mainly due to sepsis. Modern surgical techniques and improved perioperative care have significantly lowered the mortality rate. Mechanical bowel preparation (MBP) is aimed at cleansing the large bowel of fecal content thus reducing morbidity and mortality related to colorectal surgery. We carried out a study aimed to investigate the outcomes of colorectal surgery with and without MBPs, to avoid unpleasant side-effects of MBP and also to design a protocol for preparation of a patient for colorectal surgery. MATERIALS AND METHODS: This was a prospective study over a period of March 2008-May 2010 carried out at Department of General Surgery of our institution. A total of 63 patients were included in this study; among those 32 patients were operated with MBPs and 31 without it; admitted in in-patient department undergoing resection of left colon and rectum for benign and malignant conditions in both emergency and elective conditions. RESULTS: Anastomotic leakage, intra-abdominal collections was detected clinically and radiologically in 2 and 4 patients in each group respectively. P > 0.5 in both situations, indicating statistically no difference between results of two groups. Wound infections were detected in 12 (37.5%) patients with MBP group and 11 (35.48%) patients without MBP. CONCLUSION: The present results suggest that the omission of MBP does not impair healing of colonic anastomosis; neither increases the risk of leakage.

Ab initio study of CO2 capture mechanisms in aqueous monoethanolamine: reaction pathways for the direct interconversion of carbamate and bicarbonate.

Ab initio molecular orbital calculations combined with the polarizable continuum model (PCM) formalism have been carried out for a comprehensive understanding of the mechanism of carbon dioxide (CO2) absorption by aqueous amine solutions. CO2 is captured by amines to generate carbamates and bicarbonate. We have examined the direct interconversion pathways of these two species (collectively represented by a reversible hydrolysis of carbamate) with the prototypical amine, monoethanolamine (MEA). We evaluate both a concerted and a stepwise mechanism for the neutral hydrolysis of MEA carbamate. Large activation energies (ca. 36 kcal/mol) and lack of increase in catalytic efficiency with the inclusion of additional water molecules are predicted in both the mechanisms. We also examined the mechanism of alkaline hydrolysis of MEA carbamate at high concentrations of amine (high pH). The addition of OH(-) ion to carbamate anion was theoretically not allowed due to the reduction in the nucleophilicity of the former as a result of microsolvation. We propose an alternative pathway for hydrolysis: a proton transfer from protonated MEA to carbamate to generate the carbamic acid that initially undergoes a nucleophilic addition of OH(-) and subsequent low-barrier reactions leading to the formation of bicarbonate and free MEA. On the basis of the calculated activation energies, this pathway would be the most efficient route for the direct interconversion of carbamate and bicarbonate without the intermediacy of the free CO2, while the actual contributions will be dependent on the concentrations of protonated MEA and OH(-) ions.

Computational investigation of carbon dioxide absorption in alkanolamine solutions.

We investigated CO2 absorption in aqueous alkanolamine solutions using density functional theory with dielectric continuum solvation models (SMD/IEF-PCM and COSMO-RS). We varied the alkyl chain length (m = 2, 3, 4) and the alcohol chain length (n = 2, 3, 4) in the alkanolamine structures, H(CH2) m NH(CH2) n OH. Using the SMD/IEF-PCM/B3LYP/6-311++G(d,p) and COSMO-RS/BP/TZVP levels of theory, our calculations predict that the product of CO2 absorption (carbamate or bicarbonate) is strongly affected by the alcohol length but does not differ significantly by varying the alkyl chain length. This prediction was confirmed experimentally by (13)C-NMR. The observed sensitivity to the alcohol chain length can be attributed to hydrogen bonding effects. The intramolecular hydrogen bonds of HN · · · HO, NH2 (+) · · · OH, and NCOO(-) · · · HO induce ring structure formation in neutral alkanolamines, protonated alkanolamines, and carbamate anions, respectively. The results from our studies demonstrate that intramolecular hydrogen bonds play a key role in CO2 absorption reactions in aqueous alkanolamine solutions.