Rapid comprehensive characterization of crude oils by thermogravimetry coupled to fast modulated gas chromatography-single photon ionization time-of-flight mass spectrometry.

Comprehensive multi-dimensional hyphenation of a thermogravimetry device (i.e. a thermobalance) to gas chromatography and single photon ionization-time-of-flight mass spectrometry (TG-GC×SPI-MS) has been used to investigate two crude oil samples of different geographical origin. The source of the applied vacuum ultraviolet radiation is an electron beam pumped rare gas excimer lamp (EBEL). The soft photoionization favors the formation of molecular ions. Introduction of a fast, rapidly modulated gas chromatographic separation step in comparison with solely TG-SPI-MS enables strongly enhanced detection especially with such highly complex organic matrices as crude oil. In contrast with former TG-SPI-MS measurements, separation and identification of overlying substances is possible because of different GC retention times. The specific contribution of isobaric compounds to one mass signal is determined for alkanes, naphthalenes, alkylated benzenes, and other compounds.

Photoreceptor cell types in the retina of the tuatara (Sphenodon punctatus) have cone characteristics.

The tuatara Sphenodon punctatus, restricted to a few New Zealand offshore islands and now strictly protected, belongs to the Rhynchocephalia, the smallest order of extant reptiles. Earlier light microscopical studies on the retina of this species described photoreceptors with both rod- and cone-like features and the presence of a fovea. A limited amount of retinal material from S. punctatus has now allowed us to prepare the first-ever electron microscopic observations on the eye of this reptile. We were able to distinguish three types of photoreceptor, all with fine structural features characteristic of cone cells. Large single cones as well as double cones had open discs in their outer segments and straight axons with pedicle-type terminals. An additional cone type, characterized by somewhat more slender inner and outer segments, vitreally-displaced cell bodies and oblique axons, resembled short-wavelength cones known from other sauropsids. No cells with rod characteristics could be confirmed in the samples, although they might occur in retinal regions not available for this study. We conclude that the tuatara has cone-like photoreceptors, which-as in other crepuscular or nocturnal reptiles-have acquired rod-like features. The phenotypic adaptations notwithstanding, the set of photoreceptor types is quite typical of the reptilian eye and in some respects reminiscent of those seen in lizards and turtles.