Compact schemes for variable coefficient convection-diffusion equations

Fourth order accurate compact schemes for variable coefficient convection-diffusion equations are considered. A sufficient condition for stability of the schemes have been derived using a difference equation based approach. The constant coefficient problems are considered as a special case, and the unconditional stability of compact schemes for such case is proved theoretically. The condition number of the amplification matrix is also analysed, and an estimate for the same is derived. In order to verify the derived conditions numerically, MATLAB codes are provided in Appendix of the manuscript. An example is provided to support the assumption taken to assure stability

1-(2-Hy­droxy­eth­yl)-3-phenyl­thio­urea

The title compound, C9H12N2OS, was obtained unexpectedly in a multicomponent reaction of an equimolar ratio of phenyl isothio­cyanate, malononitrile and amino­ethanol. The –C(H2)–N(H)–(C=S)–N(H)– methyl­thio­urea–methane group is almost normal to the phenyl ring, with a dihedral angle of 71.13 (9)°. The N—C—C—O torsion angle is 72.8 (2)°. In the crystal, mol­ecules are connected by N—H⋯O, O—H⋯S and N—H⋯O hydrogen bonds, forming a three-dimensional network

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

BACKGROUND: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. METHODS: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. FINDINGS: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96-1·28). INTERPRETATION: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. FUNDING: National Institute for Health Research Health Services and Delivery Research Programme

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

Background: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. Methods: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. Findings: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96–1·28). Interpretation: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. Funding: National Institute for Health Research Health Services and Delivery Research Programme

Dimethyl-aluminium complexes bearing naphthyl-substituted pyridine-alkylamides as pro-initiators for the efficient ROP of ε-caprolactone

Three sterically-enhanced 2-imino-6-(1-naphthyl)pyridines, 2-{CMe=N(Ar)}-6-(1-C10H7)C5H3N [Ar = 2,6-i-Pr2C6H3 (L1dipp), 2,4,6-i-Pr3C6H2 (L1tripp), 4-Br-2,6-i-Pr2C6H2 (L1Brdipp)], differing only in the electronic properties of the N-aryl group, have been prepared in high yield by the condensation reaction of 2-{CMe=O}-6-(1-C10H7)C5H3N with the corresponding aniline. Treatment of L1dipp, L1tripp and L1Brdipp with two equivalents of AlMe3 at elevated temperature affords the distorted tetrahedral 2-(amido-prop-2-yl)-6-(1-naphthyl)pyridine aluminum dimethyl complexes, [2-{CMe2N(Ar)}-6-(1-C10H7)C5H3N]AlMe2 [Ar = 2,6-i-Pr2C6H3 (1a), 2,4,6-i-Pr3C6H2 (1b), 4-Br-2,6-i-Pr2C6H2 (1c)], in good yield. The X-ray structures of 1a–1c reveal that complexation has resulted in concomitant C–C bond formation via methyl migration from aluminum to the corresponding imino carbon in L1aryl; in solution, the restricted rotation of the pendant naphthyl group in 1 confers inequivalent methyl ligand environments. The ring opening polymerization of ε-caprolactone employing 1, in the presence of benzyl alcohol, proceeded efficiently at 30 °C producing polymers of narrow molecular weight distribution with the catalytic activities dependent on the nature of the substituent located at the 4-position of the N-aryl group with the most electron donating i-Pr derivative exhibiting the highest activity (1b > 1a > 1c); at 50 °C 1b mediates 100% conversion of the monomer to polycaprolactone (poly(CL)) in one hour. In addition to 1a, 1b and 1c, the single crystal X-ray structures are reported for L1dipp and L1tripp

Dimethyl-Aluminium Complexes Bearing Naphthyl-Substituted Pyridine-Alkylamides as Pro-Initiators for the Efficient ROP of epsilon-Caprolactone

Three sterically-enhanced 2-imino-6-(1-naphthyl)pyridines, 2-{CMe=N(Ar)}-6-(1-C10H7)C5H3N [Ar = 2,6-i-Pr2C6H3 (L1dipp), 2,4,6-i-Pr3C6H2 (L1tripp), 4-Br-2,6-i-Pr2C6H2 (L1Brdipp)], differing only in the electronic properties of the N-aryl group, have been prepared in high yield by the condensation reaction of 2-{CMe=O}-6-(1-C10H7)C5H3N with the corresponding aniline. Treatment of L1dipp, L1tripp and L1Brdipp with two equivalents of AlMe3 at elevated temperature affords the distorted tetrahedral 2-(amido-prop-2-yl)-6-(1-naphthyl)pyridine aluminum dimethyl complexes, [2-{CMe2N(Ar)}-6-(1-C10H7)C5H3N]AlMe2 [Ar = 2,6-i-Pr2C6H3 (1a), 2,4,6-i-Pr3C6H2 (1b), 4-Br-2,6-i-Pr2C6H2 (1c)], in good yield. The X-ray structures of 1a–1c reveal that complexation has resulted in concomitant C–C bond formation via methyl migration from aluminum to the corresponding imino carbon in L1aryl; in solution, the restricted rotation of the pendant naphthyl group in 1 confers inequivalent methyl ligand environments. The ring opening polymerization of ε-caprolactone employing 1, in the presence of benzyl alcohol, proceeded efficiently at 30 °C producing polymers of narrow molecular weight distribution with the catalytic activities dependent on the nature of the substituent located at the 4-position of the N-aryl group with the most electron donating i-Pr derivative exhibiting the highest activity (1b > 1a > 1c); at 50 °C 1b mediates 100% conversion of the monomer to polycaprolactone (poly(CL)) in one hour. In addition to 1a, 1b and 1c, the single crystal X-ray structures are reported for L1dipp and L1tripp