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Thioacetaldehyde was prepared by the vacuum flash pyrolysis of 1, 3, 5-trimethyl-s-trithiane and was observed spectroscopically in a rapidly flowing system. The 614 nm absorption system of CH3CHS/CH3CDS/CD3CHS/CD3CDS was recorded photographically at path lengths of 72 m. Phosophorescence excitation and emission spectra of CH3CHS were observed with a cw dye laser. The assignment of the first absorption system was made to the spin forbidden transition a 3A‘←X 1A’. The bands observed in the region of the origin proved to have a very complex structure, and were assigned to torsional transitions. The observation of several hot band progressions which could be fitted to levels derived from microwave data gave the parameters V‘3 =534.3 cm-1, F‘=6.9950 cm-1, and ν0=16 293.8 cm-1 for CH3CHS. The fit to the excited state torsional levels was less satisfactory and gave V3 =94.18 cm-1, F’=5.3608 cm-1. An analysis of the data for the other isotopic species showed that the torsional motion in the upper state was coupled to a large amplitude wagging of the aldehydic hydrogen. The observed phase shift in the torsional angle on electronic excitation was attributed to the effects of hyperconjugation between the methyl hydrogens and the π (CS) orbitals. [ABSTRACT FROM AUTHOR]

This Comment notes that Baluschev et al. [J. Appl. Phys. 101, 023101 (2007)] have used an inappropriate model to describe photon upconversion by triplet-triplet annihilation and electronic energy transfer in metalloporphyrin-organic electronic energy acceptor systems. Models that account for aggregation of the metalloporphyrins and coaggregation of the metalloporphyrins with the organic energy acceptors must be employed. Several additional pathways for photon upconversion involving excitons in aggregates are proposed. Heterospecies triplet-triplet annihilation must be considered in the coaggregated metalloporphyrin-diphenylanthracene system. [ABSTRACT FROM AUTHOR]

Introduction: The architecture of joints has potentially the greatest influence on the nature of intraarticular fractures. We analysed a large number of intra-articular fractures with two aims: (1) to determine if the pattern of injuries observed supports our conjecture that the local skeletal architecture is an important factor and (2) to investigate whether associated dislocations further affect the fracture pattern. Methods: A retrospective study of intra-articular fractures over a 3.5-year period; 1003 joints met inclusion criteria and were analysed. Three independent investigators determined if fractures affected the convex dome, the concave socket, or if both joint surfaces were involved. Further review determined if a joint dislocation occurred with the initial injury. Statistical analysis was performed using a one-way frequency table, and the X² test was used to compare the frequencies of concave and convex surface fractures. The odds ratios (ORs) were calculated to establish the association between the frequencies of concave and convex surface fractures, as well as between dislocation and either fracture surface involvement. Results: Of the 1003 fractures analysed, 956 (95.3%) involved only the concavity of the joint; in 21 fractures (2.1%) both joint surfaces were involved; and in 26 fractures (2.6%) only the convexity was involved (X² = 1654.9, df = 2, p < 0.0001). As expected, the concavity was 20.8 times more likely to fail than the convexity (11.2-36.6, 95% CI). However, the risk of fracturing the convex surface was 18.6 times higher (9.8-35.2, 95% CI) in association with a simultaneous joint dislocation, compared to those cases without a joint dislocation. Conclusions: These results very strongly support the study hypotheses: the skeletal architecture of joints clearly plays a highly significant role in determining the nature of intra-articular fractures. Intraarticular fractures involving the convexity are much more likely to be associated with a concurrent joint dislocation. [ABSTRACT FROM AUTHOR]