Fluorescence-properties and excited state interactions of 7-hydroxy-4-methylcoumarin laser dye

The effect of solvent on some photophysical properties of 7-hydroxy-4-methylcoumarin (4-methylumbelliferone) is examined. Light absorption results in the population of a locally excited (LE) first singlet state (S 1, ππ*) mixed with nπ*. This is characterized by extensive non-radiative energy dissipation on the subnanosecond time scale, which shows a sensitivity to environmental factors (solvent polarity and hydrogen-bonding ability) that may be exploited profitably in various systems of industrial and biological importance. Moreover, excellent linear correlations are established between some photophysical properties of 7-hydroxy-4-methylcoumarin and some solvent properties. The results of discussed on the basis of quantum chemical data obtained by application of the CNDO method. The fluorescence spectra in alcoholic solvents and water show complex formation via hydrogen-bonding interactions. The equilibrium constants K for complex formation (dye—water followed by ultrafast proton transfer) are determined at various temperatures. Small K values in the range 13 - 19 1 mol −1 are obtained. Some thermodynamic parameters are also determined. The results indicate an associative excited state complex with a dissociative ground state. The weak excited state complex formed with water is characterized by an extended strong blue-green fluorescence which can be attributed to tautomer formation via intramolecular proton transfer

Exploring the cost-effectiveness of high versus low perioperative fraction of inspired oxygen in the prevention of surgical site infections among abdominal surgery patients in three low- and middle-income countries

Background: This study assessed the potential cost-effectiveness of high (80–100%) vs low (21–35%) fraction of inspired oxygen (FiO2) at preventing surgical site infections (SSIs) after abdominal surgery in Nigeria, India, and South Africa. Methods: Decision-analytic models were constructed using best available evidence sourced from unbundled data of an ongoing pilot trial assessing the effectiveness of high FiO2, published literature, and a cost survey in Nigeria, India, and South Africa. Effectiveness was measured as percentage of SSIs at 30 days after surgery, a healthcare perspective was adopted, and costs were reported in US dollars ($). Results: High FiO2 may be cost-effective (cheaper and effective). In Nigeria, the average cost for high FiO2 was$216 compared with $222 for low FiO2 leading to a −$6 (95% confidence interval [CI]: −$13 to −$1) difference in costs. In India, the average cost for high FiO2 was $184 compared with$195 for low FiO2 leading to a −$11 (95$15 to −$6) difference in costs. In South Africa, the average cost for high FiO2 was$1164 compared with $1257 for low FiO2 leading to a −$93 (95% CI: −$132 to −$65) difference in costs. The high FiO2 arm had few SSIs, 7.33% compared with 8.38% for low FiO2, leading to a −1.05 (95% CI: −1.14 to −0.90) percentage point reduction in SSIs. Conclusion: High FiO2 could be cost-effective at preventing SSIs in the three countries but further data from large clinical trials are required to confirm this