Estimating the depth and shape of subglacial Lake Vostok's water cavity from aerogravity data

We use aerogravity data to estimate the water depth of subglacial Lake Vostok in East Antarctica. The inversion produces the first bathymetry map covering the entire lake. Lake Vostok consists of two sub-basins separated by a ridge with very shallow water depths. The deeper southern sub-basin is approximately double the spatial area of the smaller northern sub-basin. The close correlation between the pattern of basal melting and freezing and the bathymetric structure has important ramifications for the water circulation and the sediment deposition. We estimate the lake volume to be 5400 ± 1600 km^3

Enantioselective Protein-Sterol Interactions Mediate Regulation of Both Prokaryotic and Eukaryotic Inward Rectifier K+ Channels by Cholesterol

Cholesterol is the major sterol component of all mammalian cell plasma membranes and plays a critical role in cell function and growth. Previous studies have shown that cholesterol inhibits inward rectifier K+ (Kir) channels, but have not distinguished whether this is due directly to protein-sterol interactions or indirectly to changes in the physical properties of the lipid bilayer. Using purified bacterial and eukaryotic Kir channels reconstituted into liposomes of controlled lipid composition, we demonstrate by 86Rb+ influx assays that bacterial Kir channels (KirBac1.1 and KirBac3.1) and human Kir2.1 are all inhibited by cholesterol, most likely by locking the channels into prolonged closed states, whereas the enantiomer, ent-cholesterol, does not inhibit these channels. These data indicate that cholesterol regulates Kir channels through direct protein-sterol interactions likely taking advantage of an evolutionarily conserved binding pocket

IODP Expeditions 309 and 312 drill an intact section of upper oceanic basement into gabbros

The Integrated Ocean Drilling Program's (IODP) Expeditions 309 and 312 successfully completed the first sampling of an intact section of upper oceanic crust, through lavas and the sheeted dikes into the uppermost gabbros. Hole 1256D, which was initiated on the Ocean Drilling Program's (ODP) Leg 206, now penetrates to >1500 mbsf and >1250 m sub-basement. The first gabbroic rocks were encountered at 1407 mbsf. Below this, the hole penetrates 3c100 m into a complex zone of fractionated gabbros intruded into contact metamorphosed dikes

Additivity in classical-quantum wiretap channels

Due to Csiszár and Körner, the capacity of classical wiretap channels has a single-letter characterization in terms of the private information. For quantum wiretap channels, however, it is known that regularization of the private information is necessary to reach the capacity. Here we study hybrid classical-quantum wiretap channels in order to resolve how much quantumness is needed to witness non-additivity phenomena in Shannon information theory. For wiretap channels with quantum inputs but classical outputs, we prove that the characterization of the capacity in terms of the private information stays single-letter. Hence, entangled input states are of no asymptotic advantage in this setting. For wiretap channels with classical inputs, we show by means of explicit examples that the private information already becomes non-additive when either one of the two receivers becomes quantum (with the other receiver staying classical). This gives non-additivity examples that are not caused by entanglement and illustrates that in the wiretap model quantum adversaries are strictly different from classical adversaries

Seafloor spreading in the Weddell Sea from magnetic and gravity data

A re-compilation of magnetic data in the Weddell Sea is presented and compared with the gravity field recently derived from retracked satellite altimetry. The previously informally named 'Anomaly-T,' an cast-west trending linear positive magnetic and gravity anomaly lying at about 69degreesS, forms the southern boundary of the well-known Weddell Sea gravity herringbone. North of Anomaly-T, three major E-W linear magnetic lows are shown, and identified with anomalies cl2r, c21-29(r) and c33r. On the basis of these, and following work by recent investigators, isochrons c13, 08, c20, c21, c30, c33 and c34 are identified and extended into the western Weddell Sea. Similarly, a linear magnetic low lying along the spine of the herringbone is shown and provisionally dated at 93-96 Ma. Anomaly-T is tentatively dated to be M5n, in agreement with recent tectonic models. Although current tectonic models are generally in good agreement to the north of T, to the south interpretations differ. Some plate tectonic models have only proposed essentially north-south spreading in the region, whilst others have suggested that a period of predominantly east-west motion (relative to present Antarctic geographic coordinates) occurred during the mid-Mesozoic spreading between East and West Gondwana. We identify an area immediately to the south of T which appears to be the southerly extent of N-S spreading in the herringbone. Following recent work, the extreme southerly extent of the N-S directed spreading of the herringbone is provisionally dated M9r/M10. In the oldest Weddell Sea, immediately to the north and east of the Antarctic shelf, we see subtle features in both the magnetic and gravity data that are consistent with predominantly N-S spreading in the Weddell Sea during the earliest opening of East and West Gondwana. In between, however, in a small region extending approximately from about 50 km south of T to about 70degreesS and from approximately 40degrees to 53degreesW, the magnetic and gravity data appear to suggest well-correlated linear marine magnetic anomalies (possible isochrons) perpendicular to T, bounded and offset by less well-defined steps and linear lows in the gravity (possible fracture zones). These magnetic and gravity data southwest of T suggest that the crust here may record an E-W spreading episode between the two-plate system of East and West Gondwana prior to the initiation of the three-plate spreading system of South America, Africa and Antarctica. The E-W spreading record to the east of about 35degreesW would then appear to have been cut off at about M10 time during the establishment of N-S three-plate spreading along the South American-Antarctic Ridge and then subducted under the Scotia Ridge