Pleistocene plateau ice fields in the High Atlas, Morocco

Large ice fields (>25 km² ) formed over the Tazaghart and Iouzagner plateaux of the High Atlas, Morocco, during the Late Pleistocene. The plateau ice fields were drained by large valley glaciers forming a series of moraine assemblages. Four moraine units have been mapped and subdivided on the basis of morphostratigraphy and the degree of soil weathering. Soil profile development index (PDI) values indicate that the moraine units are widely separated in time with the oldest moraines deeply weathered and degraded whereas soils are absent on the youngest moraines. The highest moraine unit was formed by a small niche glacier which was present as recently as the mid 20th Century. Pleistocene glaciers are likely to have been associated with wetter conditions than today in addition to colder air temperatures. Combined with ice in neighbouring areas, such as the Toubkal Massif, the SW High Atlas supported some of the largest glaciers in Africa during the Pleistocene. The extent of glaciation with ice exploiting and breaching drainage divides has major implications for landscape development. The evolution of the High Atlas is therefore strongly shaped by glaciation and this is closely intertwined with tectonic, fluvial and slope processes

Pleistocene glaciation of Fenland, England, and its implications for evolution of the region.

Detailed investigation of landforms and their underlying deposits on the eastern margin of Fenland, East Anglia, demonstrated that they represent a series of glaciofluvial delta-fan and related sediments. Associated with these deposits are glacially dislocated sediments including tills, meltwater and pre-existing fluvial sediments. These 'Skertchly Line' deposits occur in the context of a substantial ice lobe that entered Fenland from the N to NE, dammed the streams entering the basin and caused glacial lakes to form in the valleys on the margins. Bulldozing by the ice lobe caused a series of ice-pushed ridges to form at the dynamic margin, especially at the ice maximum and during its retreat phases. Meltwater formed a series of marginal fans that coalesced into marginal accumulations in the SE of the basin. The ice lobe is named the Tottenhill glaciation. Further investigations of the Fenland margin have revealed the extent of the Tottenhill glaciation in the Fenland Basin, to the south and west, in sufficient detail to demonstrate the nature of the Tottenhill ice lobe and the landscape left on deglaciation. The ice lobe is likely to have been prone to surging. This is indicated by the low gradient of the ice lobe, the presence of underlying ductile Mesozoic clays, the evidence of ice-marginal flooding and the presence of arcuate glaciotectonic push moraines. Regional correlation, supported by independent numerical geochronology, indicates that the glaciation occurred ca 160 ka, i.e. during the late Middle Pleistocene, Marine Isotope Stage (MIS) 6, the Wolstonian Stage. Comparison and correlation across the southern North Sea Basin confirms that the glaciation is the equivalent of that during the Late Saalian Drenthe Stadial in The Netherlands. The implications of this correlation are presented. Before the glaciation occurred, the Fenland Basin did not exist. It appears to have been initiated by a subglacial tunnel valley system beneath the Anglian (=Elsterian, MIS 12) ice sheet. During the subsequent Hoxnian (=Holsteinian; approx. MIS 11) interglacial, the sea invaded the drainage system inherited following the glacial retreat. The evolution through the subsequent ca 200 ka Early to Middle Wolstonian substages, the interval between the Hoxnian (Holsteinian) temperate Stage and the Wolstonian glaciation, represents a period during which fluvial and periglacial activity modified the landscape under cold climates, and organic sediments were laid down during a warmer event. Palaeolithic humans were also periodically present during this interval, their artefacts having been reworked by the subsequent glaciation. The deglaciation was followed by re-establishment of the rivers associated with the deposition of Late Wolstonian (Warthe Stadial) gravels and sands, and later, deposits of the Ipswichian interglacial (=Eemian, approx. MIS 5e) including freshwater, then estuarine sediments. Subsequent evolution of the basin occurred during the Devensian Stage (=Weichselian, MIS 5d-2) under predominantly cold, periglacial conditions

Global glacier dynamics during 100 ka Pleistocene glacial cycles

AbstractIce volume during the last ten 100 ka glacial cycles was driven by solar radiation flux in the Northern Hemisphere. Early minima in solar radiation combined with critical levels of atmospheric CO2drove initial glacier expansion. Glacial cycles between Marine Isotope Stage (MIS) 24 and MIS 13, whilst at 100 ka periodicity, were irregular in amplitude, and the shift to the largest amplitude 100 ka glacial cycles occurred after MIS 16. Mountain glaciers in the mid-latitudes and Asia reached their maximum extents early in glacial cycles, then retreated as global climate became increasingly arid. In contrast, larger ice masses close to maritime moisture sources continued to build up and dominated global glacial maxima reflected in marine isotope and sea-level records. The effect of this pattern of glaciation on the state of the global atmosphere is evident in dust records from Antarctic ice cores, where pronounced double peaks in dust flux occur in all of the last eight glacial cycles. Glacier growth is strongly modulated by variations in solar radiation, especially in glacial inceptions. This external control accounts for ~50–60% of ice volume change through glacial cycles. Internal global glacier–climate dynamics account for the rest of the change, which is controlled by the geographic distributions of glaciers.</jats:p

Изменение микроструктуры пружинного Сr-Ni сплава после старения

Установлено, что старение закаленного сплава 47ХНМ при температуре 500 °С в течение 5...10 ч не приводит к распаду пересыщенного твердого раствора, при повышении температуры старения до 600 °С начинают проявляться признаки распада в частицах ?-фазы гомогенного типа. Показано, что после старения при 700 °С закаленных образцов интенсивно развивается прерывистый распад с выделением некогерентной ?-фазы на основе хрома, причем объемная доля его возрастает с увеличением времени старения, достигая максимальных значений за 5...10 ч старения

Structure and Transport in Coatings from Multiscale Computed Tomography of Coatings-New Perspectives for Eelectrochemical Impedance Spectroscopy Modeling?

Computed Tomography (CT) is an approach that has been extensively applied in many areas of science from understanding structures in living organisms to materials science. In materials science, the study of structures within coatings presents challenges on at least two different levels. First, the structure of the coatings needs to be understood from the atomic scale, where dissolution reactions begin, up to length scales which cover the aggregation of inhibitors and other additives, which take place at ∼10−5 m, i.e. 4 to 5 orders of magnitude. CT is a favourable imaging technique since it allows multiscale information to be obtained non-destructively down to tens of nanometres. In this study X-ray absorption contrast imaging has been used to examine structures created using strontium chromate (SrCrO4) particles embedded in an epoxy film. It has been found that SrCrO4 particles can form clusters that extend a few hundred microns in the plane of the film, span the thickness of the film and have fractal characteristics. There are also volumes of low density epoxy of similar sizes and characteristics to the SrCrO4 clusters. The SrCrO4 clusters have a strong influence on the leaching behaviour since the release changes with time. Initially, leaching is controlled by direct dissolution but, as the clusters dissolve, the release is dominated by the fractal dimension of the cluster. The dissolved clusters leave behind voids filled with electrolyte that provide alternative transport pathways for corrosive ions through the polymer. In this paper, the nature of these clusters will be reviewed and the implication for transport properties and electrochemical assessment will be explored

Theoretical size distribution of fossil taxa: analysis of a null model

BACKGROUND: This article deals with the theoretical size distribution (of number of sub-taxa) of a fossil taxon arising from a simple null model of macroevolution. MODEL: New species arise through speciations occurring independently and at random at a fixed probability rate, while extinctions either occur independently and at random (background extinctions) or cataclysmically. In addition new genera are assumed to arise through speciations of a very radical nature, again assumed to occur independently and at random at a fixed probability rate. CONCLUSION: The size distributions of the pioneering genus (following a cataclysm) and of derived genera are determined. Also the distribution of the number of genera is considered along with a comparison of the probability of a monospecific genus with that of a monogeneric family

The Impact of Lab4 Probiotic Supplementation in a 90-Day Study in Wistar Rats

The anti-inflammatory and cholesterol lowering capabilities of probiotic bacteria highlight them as potential prophylactics against chronic inflammatory diseases, particularly cardiovascular disease. Previous studies in silico, in vitro, and in vivo suggest that the Lab4 probiotic consortium may harbour such capabilities and in the current study, we assessed plasma levels of cytokines/chemokines, short chain fatty acids and lipids and faecal levels of bile acids in a subpopulation of healthy Wistar rats included in 90-day repeat dose oral toxicity study. In the rats receiving Lab4, circulating levels of pro-inflammatory interleukin-6, tumour necrosis factor-α and keratinocyte chemoattractant/growth regulated oncogene were significantly lower compared to the control group demonstrating a systemic anti-inflammatory effect. These changes occurred alongside significant reductions in plasma low density lipoprotein cholesterol and increases in faecal bile acid excretion implying the ability to lower circulating cholesterol via the deconjugation of intestinal bile acids. Correlative analysis identified significant associations between plasma tumour necrosis factor-α and the plasma total cholesterol:high density lipoprotein cholesterol ratio and faecal levels of bifidobacteria in the Lab4 rats. Together, these data highlight Lab4 supplementation as a holistic approach to CVD prevention and encourages further studies in humans