Pyrolytic elimination of ethylene from ethoxyquinolines and ethoxyisoquinolines: a computational study

This work reports a thermo-kinetic study on unimolecular thermal decomposition of some ethoxyquinolines and ethoxyisoquinolines derivatives (1-ethoxyisoquinoline (1-EisoQ), 2-ethoxyquinoline (2-EQ), 3-ethoxyquinoline (3-EQ), 3-ethoxyisoquinoline (3-EisoQ), 4-ethoxyquinoline (4-EQ), 4-ethoxyisoquinoline (4-EisoQ), 5-ethoxyquinoline (5-EQ), 5-ethoxyisoquinoline (5-EisoQ), 8-ethoxyquinoline (8-EQ) and 8-ethoxyisoquinoline (8-EisoQ)) using density functional theory DFT (BMK, MPW1B95, M06-2X) and ab initio complete basis set-quadratic Becke3 (CBS-QB3) calculations. In the course of the decomposition of the investigated systems, ethylene is eliminated with the production of either keto or enol tautomer. The six-membered transition state structure encountered in the path of keto formation is much lower in energy than the four-membered transition state required to give enol form. Rate constants and activation energies for the decomposition of 1-EisoQ, 2-EQ, 3-EQ, 3-EisoQ, 4-EQ, 4-EisoQ, 5-EQ, 5-EisoQ, 8-EQ, and 8-EisoQ have been estimated at different temperatures and pressures using conventional transition state theory combined with Eckart tunneling and the unimolecular statistical Rice–Ramsperger–Kassel–Marcus theories. The tunneling correction is significant at temperatures up to 1000 K. Rate constants results reveal that ethylene elimination and keto production are favored kinetically and thermodynamically over the whole temperature range of 400–1200 K and the rates of the processes under study increase with the rising of pressure up to 1 atm.This paper is dedicated to the soul of the late Prof. Dr. Ahmed El-Nahas, without whom this project would never have been possible.Scopu

Ciprofioxacin in experimental Pseudomonas aeruginosa meningitis in rabbits

The potential of ciprofloxacin for the therapy of Pseudomonas aeruginosa meningitis was evaluated in an animal model by determining the penetration of the drug into CSF, its concentration-dependent killing characteristics in vivo, and its relative efficacy compared with ceftazidime and tobramycin. Meningitis was produced in 40 rabbits by intracisternal injection of 3 x 10 7 organisms. The drugs were administered intravenously over seven hours, and simultaneous serum and CSF samples were taken at 0, 1, 3, 5, and 7 h for determination of drug concentration and CSF bacterial counts. The percentage penetration of ciprofloxacin (18-4± 12'3; mean±standard deviation) in infected rabbits was substantially increased over that found in uninfected rabbits (4'1 ± 1· 3). The rate of bacterial killing for animals treated with ceftazidime (100 mg/kg/h) and high doses of tobramycin (2·5 mg/kg/h) was -0·51 ±0·13 (lOglO cfu/ml/h). This was similar to the rate of killing (-0-48±0·2) found when ciprofloxacin was infused at 5 mg/kg/h, a dose that produced a mean serum level of 6·7 ± 4·6 mg/I, which corresponds to concentrations achievable in humans. As dosages were increased (15 and 30 mg/kg/h), the rate of bacterial killing also increased (-0'70 ±O'I and -0·89±0·4 respectively; r = 0·7407; P<O·OI). The drug shows promise in the treatment of pseudomonas meningitis

Serotype distribution of Streptococcus pneumoniae causing invasive disease in children in the post-PCV era:A systematic review and meta-analysis

BACKGROUND:Routine immunisation with pneumococcal conjugate vaccines (PCV7/10/13) has reduced invasive pneumococcal disease (IPD) due to vaccine serotypes significantly. However, an increase in disease due to non-vaccine types, or serotype replacement, has been observed. Serotypes' individual contributions to IPD play a critical role in determining the overall effects of PCVs. This study examines the distribution of pneumococcal serotypes in children to identify leading serotypes associated with IPD post-PCV introduction. METHODS:A systematic search was performed to identify studies and surveillance reports (published between 2000 and December 2015) of pneumococcal serotypes causing childhood IPD post-PCV introduction. Serotype data were differentiated based on the PCV administered during the study period: PCV7 or higher valent PCVs (PCV10 or PCV13). Meta-analysis was conducted to estimate the proportional contributions of the most frequent serotypes in childhood IPD in each period. RESULTS:We identified 68 studies reporting serotype data among IPD cases in children. We analysed data from 38 studies (14 countries) where PCV7 was administered and 20 (24 countries) where PCV10 or PCV13 have been introduced. Studies reported early and late periods of PCV7 administration (range: 2001∓13). In these settings, serotype 19A was the most predominant cause of childhood IPD, accounting for 21.8% (95%CI 18.6∓25.6) of cases. In countries that have introduced higher valent PCVs, study periods were largely representative of the transition and early years of PCV10 or PCV13. In these studies, the overall serotype-specific contribution of 19A was lower (14.2% 95%CI 11.1∓18.3). Overall, non-PCV13 serotypes contributed to 42.2% (95%CI 36.1∓49.5%) of childhood IPD cases. However, regional differences were noted (57.8% in North America, 71.9% in Europe, 45.9% in Western Pacific, 28.5% in Latin America, 42.7% in one African country, and 9.2% in one Eastern Mediterranean country). Predominant non-PCV13 serotypes overall were 22F, 12F, 33F, 24F, 15C, 15B, 23B, 10A, and 38 (descending order), but their rank order varied by region. CONCLUSION:Childhood IPD is associated with a wide number of serotypes. In the early years after introduction of higher valent PCVs, non-PCV13 types caused a considerable proportion of childhood IPD. Serotype data, particularly from resource-limited countries with high burden of IPD, are needed to assess the importance of serotypes in different settings. The geographic diversity of pneumococcal serotypes highlights the importance of continued surveillance to guide vaccine design and recommendations

Optical resolution of oriented enantiomers via photodissociation: Quantum simulations for H2POSD

We demonstrate quantum mechanically how to resolve enantiomers from an oriented racemic mixture taking advantage of photodissociation. Our approach employs a femtosecond ultraviolet (UV) laser pulse with specific linear polarization achieving selective photodissociation of one enantiomer from a mixture of L and D enantiomers. As a result, the selected enantiomer is destroyed in the electronic excited state while the opposite counter enantiomer is left intact in the ground state. As an example we use H2POSD which presents axial chirality. A UV pulse excites the lowest singlet excited state which has nσ* character and is, therefore, strongly repulsive along the P-S bond. The model simulations are performed using wavepackets which propagate on two dimensional potential energy surfaces, calculated along the chirality and dissociation reaction coordinates using CASSCF level of theory

Theoretical study on cation codoped SrTiO₃ photocatalysts for water splitting

The large band gap of SrTiO3 is disadvantageous for photocatalytic applications. We therefore study cation codoping to modify the size of the band gap and extend the absorption to visible light. We identify efficient codoping schemes that guarantee charge compensation to avoid creation of localized states. Using the Heyd-Scuseria-Ernzerhof hybrid functional, we analyze the crystal and electronic structures as well as the optical properties. It is found that (Nb/Ta, Ga/In) codoping does not reduce the band gap, in contrast to (Mo/W, Zn/Cd) codoping. The position of the conduction band edge after (Mo, Cd) codoping impedes a high photocatalytic efficiency, whereas (Mo/W, Zn) and (W, Cd) codoping are found to be favorable.Accepted Author ManuscriptEngineering Thermodynamic

Optimized long-range corrected density functionals for electronic and optical properties of bare and ligated CdSe quantum dots

The reliable prediction of optical and fundamental gaps of finite size systems using density functional theory requires to account for the potential self-interaction error, which is notorious for degrading the description of charge transfer transitions. One solution is provided by parametrized long-range corrected functionals such as LC-BLYP, which can be tuned such as to describe certain properties of the particular system at hand. Here, bare and 3-mercaptoprotionic acid covered Cd33Se33 quantum dots are investigated using the optimally tuned LC-BLYP functional. The range separation parameter, which determines the switching on of the exact exchange contribution, is found to be 0.12 bohr-1 and 0.09 bohr-1 for the bare and covered quantum dot, respectively. It is shown that density functional optimization indeed yields optical and fundamental gaps and thus exciton binding energies, considerably different compared with standard functionals such as the popular PBE and B3LYP ones. This holds true, despite the well established fact that the leading transitions are localized on the quantum dot and do not show pronounced long-range charge transfer character. 2016 American Chemical SocietyGrant: This work was made possible by NPRP grant #NPRP 7-227-1- 034 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Optimized long-range corrected density functionals for electronic and optical properties of bare and ligated CdSe quantum dots

The reliable prediction of optical and fundamental gaps of finite size systems using density functional theory requires to account for the potential self-interaction error, which is notorious for degrading the description of charge transfer transitions. One solution is provided by parametrized long-range corrected functionals such as LC-BLYP, which can be tuned such as to describe certain properties of the particular system at hand. Here, bare and 3-mercaptoprotionic acid covered Cd33Se33 quantum dots are investigated using the optimally tuned LC-BLYP functional. The range separation parameter, which determines the switching on of the exact exchange contribution, is found to be 0.12 bohr-1 and 0.09 bohr-1 for the bare and covered quantum dot, respectively. It is shown that density functional optimization indeed yields optical and fundamental gaps and thus exciton binding energies, considerably different compared with standard functionals such as the popular PBE and B3LYP ones. This holds true, despite the well established fact that the leading transitions are localized on the quantum dot and do not show pronounced long-range charge transfer character