Ueber die Zuverl?ssigkeit der Rauchgasanalysen

Ohne Zusammenfassung     

Measurement of franck-condon factors for the υ′= 0 progression in the BX system of PO

Laser fluorescence of PO produced in a microwave discharge through organophosphonate esters has been studied. The flourescence was pumped in the B²Σ⁺-X²Π 3250 Å system. Relative intensities of fluorescence for the υ′= 0 progression were measured. These intensities were used to derive Franck-Condon factors for the υ′= 0 progression.     

A pseudoatom approach to molecular truncation: application in ab initio MBPT methods

In this paper, we test the performance of the molecular truncation method of Mallik et al., which was originally applied at the semiempirical NDDO level, in ab initio MBPT methods. Pseudoatoms developed for the replacement of -OCH(3) and -OCH(2)CH(3) functional groups are used in optimizations of selected clusters, and the resulting geometries are compared to reference values taken from the full molecules. It is shown that the pseudoatoms, which consist of parametrized effective core potentials for the nearest neighbor interactions and an external charge field for long-range Coulomb effects, perform well at the MP2 and CCSD levels of theory for the suite of molecules to which they were applied. Representative timings for some of the pseudoatom-terminated clusters are presented, and it is seen that there is a significant reduction in computational time, yet the geometric configurations and deprotonation energies of the pseudoatom-terminated clusters are comparable to the more computationally expensive all-atom molecules.     

Die Werthbestimmung der Kohle

Ohne Zusammenfassung     

A liposomal dispersion formulation of propofol: formulation, pharmacokinetics, stability, and identification of an oxidative degradant

Propofol is a common and highly effective anesthetic. Commercially available formulations of propofol, which is only sparingly soluble in aqueous systems, utilize emulsion technology. A liposome based dispersion formulation of propofol has been produced which exhibits good long term colloidal and chemical stability and pharmacokinetcs indistinguishable from the emulsion systems. Inclusion of 0.01% ascorbic acid in the final formulation arrests the growth of an oxidative degradant of propofol both during production and on stability. This degradant is identified as being the dimer 4,4′-dihydroxy-3,3′, 5,5′-tetraisopropylbiphenyl by mass spectroscopy and comparison of the infrared spectrum of the purified degradant to predicted spectra generated using density functional theory.     

A Re‐Examination of the Reaction of 3,4‐Diamino[1,2,5]oxadiazole with Glyoxal

Reaction coordinate mapping was used to study the reaction of 3,4‐diamino[1,2,5]oxadiazole (3,4‐diaminofurazan) and 3,4‐diamino[1,2,5]thiadiazole with glyoxal. The thiadiazole was known to give a good yield of [1,2,5]thiadiazolo[3,4‐b]pyrazine, whereas the oxadiazole had not yielded, until now, [1,2,5]oxadiazolo[3,4‐b]pyrazine (or furazano[2,3‐b]pyrazine). The calculations suggested that the diols, 5,6‐dihydroxy‐4,5,6,7‐tetrahydro[1,2,5]oxadiazolo[3,4‐b]pyrazine and 5,6‐dihydroxy‐4,5,6,7‐tetrahydro[1,2,5]thiadiazolo[3,4‐b]pyrazine should be stable intermediates, and once formed, should provide a pathway to the target compounds via two dehydration steps, under forcing conditions. With this information in mind, the reactions of 3,4‐diamino[1,2,5]oxadiazole with glyoxal and pyruvic aldehyde were re‐examined. The reaction of 3,4‐diamino[1,2,5]oxadiazole with glyoxal and pyruvic aldehyde produced, under slightly basic conditions, a near quantitative yield of the expected initial products, 5,6‐dihydroxy‐4,5,6,7‐tetrahydro[1,2,5]oxadiazolo[3,4‐b]pyrazine and the 5‐methyl analog, respectively. The diols were easily isolated by lyophilizing the aqueous reaction mixture. The diols were pyrolized on silica gel at 160°C to give the desired [1,2,5]oxadiazolo[3,4‐b]pyrazine and the 5‐methyl analog. Both compounds were easily reduced to the corresponding 4,5,6,7‐tetrahydro‐derivative using sodium borohydride in THF/methanol. The [1,2,5]oxadiazolo[3,4‐b]pyrazine also displayed other interesting chemistry.