Interstellar reddening is determined for a number of recent novae based upon emission-line ratios which are generally observable using CCDs. Large values of extinction are found for most systems, ...possibly indicative of an intrinsic component of reddening in postoutburst novae. The unusual characteristics of the (O I) lines in novae, which are strong and optically thick, require a large population of very dense globules which are the likely sites of dust formation. These pyroclasts must be ejected from the white dwarf. The total mass of the neutral gas in the globules in some of the objects is substantially larger than the masses normally derived for the ionized ejecta of novae. The distribution of radial velocities of Galactic novae in the Tololo sample, although uncertain, shows an asymmetry in having predominantly negative values. Either high internal absorption in the expanding ejecta skews the emission lines to bluer wavelengths, or most of the novae are moving out from the center of the Galaxy.
A series of analogs of terfenadine has been prepared to probe the structural requirements for hERG and H
1 binding affinity.
In the late 1980’s reports linking the non-sedating antihistamines ...terfenadine and astemizole with torsades de pointes, a form of ventricular tachyarrhythmia that can degenerate into ventricular fibrillation and sudden death, appeared in the clinical literature. A substantial body of evidence demonstrates that the arrhythmogenic effect of these cardiotoxic antihistamines, as well as a number of structurally related compounds, results from prolongation of the QT interval due to suppression of specific delayed rectifier ventricular K+ currents via blockade of the hERG-IKr channel. In order to better understand the structural requirements for hERG and H
1 binding for terfenadine, a series of analogs of terfenadine has been prepared and studied in both in vitro and in vivo hERG and H
1 assays.
The 11B chemical shift assignment for the closo-carborane C,3-Me2-1,2-C2B3H3 structure (1a or 1b) is refuted by ab initio/IGLO, GIAO/NMR evaluations. Attempts to reproduce the literature NMR data by ...examining the computed chemical shifts of many alternative structures failed. Rearrangement of the 1,2-C2B3H5 isomer into the much more stable 1,5-C2B3H5 is computed to involve only a modest energy barrier. Repetition of the thermal (but not the electric discharge) experiments failed to give a compound with the spectroscopic data reported earlier. The original experimental data remain unexplained. Nevertheless, the elimination of the C,3-Me2-1,2-C2B3H3 structural assignment removes the sole exception to four established structural patterns of closo-carboranes: (a) carbons tend to occupy sites with the lowest coordination, (b) carbons tend to be nonadjacent in the most thermodynamically stable closo-carboranes, (c) the 11B NMR of boron atoms with exo-terminal alkyl groups are always found at lower field than those of otherwise identical boron atoms with exo-terminal hydrogens, and (d) exo-terminal δ(1H)'s normally parallel the δ(11B) of the boron nuclei to which they are bound.
Structures of carborane cations derived from the reaction of 2-propyl cation with diborane have been re-investigated by the DFT/IGLO/GIAO-MP2/NMR method. Based on the results the earlier proposed ...compound,
arachno-Me
2CBH
4
+ (
4) was not obtained. The carborane,
arachno-MeC
2BH
7
+ (
5) (3.4 kcal mol
−1 more stable than
4) is a better candidate for the second species observed.
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