Weathering characteristics and lithology of samples from the Rauer Group, Antarctica, obtained in February/March 2007, and conducted with field support of POLARSTERN cruise ANT-XXIII/9

The presence of glacial sediments across the Rauer Group indicates that the East Antarctic ice sheet formerly covered the entire archipelago and has since retreated at least 15 km from its maximum extent. The degree of weathering of these glacial sediments suggests that ice retreat from this maximum position occurred sometime during the latter half of the last glacial cycle. Following this phase of retreat, the ice sheet margin has not expanded more than ~1 km seaward of its present position. This pattern of ice sheet change matches that recorded in Vestfold Hills, providing further evidence that the diminutive Marine Isotope Stage 2 ice sheet advance in the nearby Larsemann Hills may have been influenced by local factors rather than a regional ice-sheet response to climate and sea-level change.

Physical oceanography, sea-bed photographs and videos of benthos from the Weddell Sea taken with remote operated vehicle CHEROKEE during POLARSTERN cruise ANT-XXIII/8

The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabenthic shelf species interspersed. Antarctic Minke whales and seals utilised the Larsen A/B area to feed on presumably newly established krill and pelagic fish biomass. Ecosystem impacts also extended well beyond the zone of ice-shelf collapse, with areas of high benthic disturbance resulting from scour by icebergs discharged from the Larsen embayments.

An Empirical Investigation of Learning From the Semantic Web

Peer reviewed

Teenagers and dog take refuge from the rain in Central Park, New York

Inscriptions: Verso: [stamped] Photograph by Freda Leinwand. [463 West Street, Studio 229G, New York, NY 10014].

Analyses of hydrocarbon gases and sulphate in sediments from the King George Basin, Antarctica

Thermogenic hydrocarbons, formed by the thermal alteration of organic matter, are encountered in several piston core stations in the King George Basin, Anatarctica. These hemipelagic sediments are being deposited in an area of active hydrothermalism, associated with the back-arc spreading in the Bransfield Strait. The lateral extent of sediments infiltrated by the hydrothermally influenced interstitial fluids is characterized by basalt diapiric intrusions and is delineated by an acoustically turbid zone in the sediments of the eastern part of the basin. Iron-sulphide-bearing veins and fractures cut across the sediment in several cores; they appear to be conduits for flow of hydrothermally altered fluids. These zones have the highest C2+ and ethene contents. The thermogenic hydrocarbons have molecular C1/(C2 + C3) ratios typically < 50 and delta13CH4 values between -38? and -48?, indicating an organic source which has undergone strong thermal stress. Several sediment cores also have mixed gas signatures, which indicate the presence of substantial amounts of bacterial gas, predominantly methane. Hydrocarbon generation in the King George Basin is thought to be a local phenomenon, resulting from submarine volcanism with temperatures in the range 70-150°C. There are no apparent seepages of hydrocarbons into the water column, and it is not believed that significant accumulation of thermogenic hydrocarbons reside in the basin.

Paleotemperatures, stable isotopes and alkenones of samples from the South Atlantic

Carbon dioxide is one of the most important greenhouse gases which are increasing in atmospheric concentration due to human activities. For using natural CO2 dynamics as a key to understanding the climatic consequences of anthropogenic pCO2 rise, the ocean plays an important role due to its much larger carbon pool compared to the atmosphere. By studying the ratio of stable carbon isotopes in organic matter from marine sediments, it is possible to estimate the partial pressure of CO2 in surface waters during ancient times. The organic compound C37:2 alkenone, whose sole origin is from autotrophic marine algae, was chosen for d13C analysis and its isotopic composition used to reconstruct past PCO2 levels in the surface layer of the eastern Angola Basin for the last 200,000 years. In addition to the variation of ancient concentrations of dissolved CO2 ([CO2(aq)] = ce), the effect of carbon demand which depends on algal growth rate was considered. Here to, carbon isotopic fractionation of C37:2 alkenones (ep) in core-top sediments from the equatorial and the South Atlantic was calibrated against pre-industrial [CO2(aq)] and phosphate concentrations in surface waters. From these data, a variable b = (25 per mil - ep) * ce which reflects intracellular carbon demand was calculated. This variable b correlates with the ambient concentration of seawater phosphate and depends on growth rates. The bulk sediment d15N was used as a proxy parameter for calculating ancient b-values, taking into account that d15N in core-top sediments is correlated to phosphate concentration in modern surface waters. On this basis, the alkenone d13C record of GeoB1016-3 documents a permanent oceanic source for atmospheric carbon dioxide during the last 200,000 years. As a consequence of using d15N derived b-values instead of b = constant, the Angola Basin appears to have been an even stronger CO2 source during glacial periods than at present. Qualitatively similar results were reported by Jasper et al. (1994) for the central Equatorial Pacific. These observations suggest that enhanced productivity of low-latitude upwelling areas during glacial periods is not responsible for the lower CO2 content of the glacial atmosphere.

The association between spastic Cerebral Palsy, intellectual impairment, and gestational age: results from the Northern Ireland Cerebral Palsy Register

Background
Studies suggest a complex relationship between Cerebral Palsy sub-types, severity of impairment, and risk factors such as gestational age. To investigate these relationships, we conducted analyses on over 1,100 children included in the Northern Ireland Cerebral Palsy Register (NICPR) whose clinical CP subtype was Bilateral Spastic or Spastic Hemiplegia, and for whom information was available on the relevant variables.
Methods
We tested for the association between Bilateral and Hemiplegia subtypes, severe intellectual impairment, and gestational age (term; moderately preterm; very or extremely preterm) while controlling for gender, socio-economic deprivation, year of birth, and birth weight (using a standardized birth-weight score based on deviance from the birth weight average within each gestational age band). Severity of intellectual impairment was dichotomised (severe intellectual delay vs. moderate or no delay).
Results
Logistic regressions indicated a good fit of the model, and the predictors included explained approximately 19% of variability in the outcome. The results indicated a strong association between the Bilateral subtype and severe intellectual impairment: compared to children with the Hemiplegia subtype, those with Bilateral Spastic CP displayed a 10-fold increase in the odds of severe intellectual impairment. The results revealed a significant interaction between CP subtype and gestational age: for the Bilateral CP subtype, being born at term was associated with increased probability of severe intellectual impairment.
Discussion
Results are consistent with other studies (Hemming et al., 2008) in indicating that the likelihood of cognitive impairments increases with increasing gestational age at delivery of Bilateral Spastic CP children. The results are discussed in light of hypotheses that suggest the brain might be able to reorganise and compensate the effects of lesions and injuries when it is still less developed.