Ultra-shallow-marine anoxia in an Early Triassic shallow-marine clastic ramp (Spitsbergen) and the suppression of benthic radiation

Lower Triassic marine strata in Spitsbergen accumulated on a mid-to-high latitude ramp in which high-energy foreshore and shoreface facies passed offshore into sheet sandstones of probable hyperpycnite origin. More distal facies include siltstones, shales and dolomitic limestones. Carbon isotope chemostratigraphy comparison allows improved age dating of the Boreal sections and shows a significant hiatus in the upper Spathian. Two major deepening events, in earliest Griesbachian and late Smithian time, are separated by shallowing-upwards trends that culminated in the Dienerian and Spathian substages. The redox record, revealed by changes in bioturbation, palaeoecology, pyrite framboid content and trace metal concentrations, shows anoxic phases alternating with intervals of better ventilation. Only Dienerian–early Smithian time witnessed persistent oxygenation that was sufficient to support a diverse benthic community. The most intensely anoxic, usually euxinic, conditions are best developed in offshore settings, but at times euxinia also developed in upper offshore settings where it is even recorded in hyperpycnite and storm-origin sandstone beds: an extraordinary facet of Spitsbergen's record. The euxinic phases do not track relative water depth changes. For example, the continuous shallowing upwards from the Griesbachian to lower Dienerian was witness to several euxinic phases separated by intervals of more oxic, bioturbated sediments. It is likely that the euxinia was controlled by climatic oscillations rather than intra-basinal factors. It remains to be seen if all the anoxic phases found in Spitsbergen are seen elsewhere, although the wide spread of anoxic facies in the Smithian/Spathian boundary interval is clearly a global event

An abrupt extinction in the Middle Permian (Capitanian) of the Boreal Realm (Spitsbergen) and its link to anoxia and acidification

The controversial Capitanian (Middle Permian, 262 Ma) extinction event is only known from equatorial latitudes, and consequently its global extent is poorly resolved. We demonstrate that there were two, severe extinctions amongst brachiopods in northern Boreal latitudes (Spitsbergen) in the Middle to Late Permian, separated by a recovery phase. New age dating of the Spitsbergen strata (belonging to the Kapp Starostin Formation), using strontium isotopes and d13C trends and comparison with better-dated sections in Greenland, suggests that the first crisis occurred in the Capitanian. This age assignment indicates that this Middle Permian extinction is manifested at higher latitudes. Redox proxies (pyrite framboids and trace metals) show that the Boreal crisis coincided with an intensification of oxygen depletion, implicating anoxia in the extinction scenario. The widespread and near-total loss of carbonates across the Boreal Realm also suggests a role for acidification in the crisis. The recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors, and an increased mollusk dominance, resulting in an assemblage reminiscent of younger Mesozoic assemblages. The subsequent end-Permian mass extinction terminated this Late Permian radiation

Technique for producing highly planar Si/SiO0.64Ge0.36/Si metal–oxide–semiconductor field effect transistor channels

Si/Si0.64Ge0.36/Si heterostructures have been grown at low temperature (450 °C) to avoid the strain-induced roughening observed for growth temperatures of 550 °C and above. The electrical properties of these structures are poor, and thought to be associated with grown-in point defects as indicated in positron annihilation spectroscopy. However, after an in situ annealing procedure (800 °C for 30 min) the electrical properties dramatically improve, giving an optimum 4 K mobility of 2500 cm2 V – 1 s – 1 for a sheet density of 6.2 × 1011 cm – 2. The low temperature growth yields highly planar interfaces, which are maintained after anneal as evidenced from transmission electron microscopy. This and secondary ion mass spectroscopy measurements demonstrate that the metastably strained alloy layer can endure the in situ anneal procedure necessary for enhanced electrical properties. Further studies have shown that the layers can also withstand a 120 min thermal oxidation at 800 °C, commensurate with metal–oxide–semiconductor device fabrication

Effective mobilities in pseudomorphic Si/SiGe/Si p-channel metal-oxide-semiconductor field-effect transistors with thin silicon capping layers

The room-temperature effective mobilities of pseudomorphic Si/Si0.64Ge0.36/Si p-metal-oxidesemiconductor field effect transistors are reported. The peak mobility in the buried SiGe channel increases with silicon cap thickness. It is argued that SiO2/Si interface roughness is a major source of scattering in these devices, which is attenuated for thicker silicon caps. It is also suggested that segregated Ge in the silicon cap interferes with the oxidation process, leading to increased SiO2/Si interface roughness in the case of thin silicon caps

Steps to a neurochemistry of personality [Letter]

Depue & Collins's (D&C's) work relies on extrapolation from data obtained through studies in experimental animals, and needs support from studies of the role of dopamine (DA) neurotransmission in human behaviour. Here we review evidence from two sources: (1) studies of patients with Parkinson's disease and (2) positron emission tomography (PET) studies of DA neurotransmission, which we believe lend support to Depue & Collins's theory, and which can potentially form the basis for a true neurochemistry of personality