Pisces IV submersible observations in the epicentral region of the 1929 Grand Banks earthquake

The PISCES IVsubmersible was used to investigate the upper continental slope around 44 ON, 56 W, near the epicentre of the 1929 Grand Banks earthquake. Four dives in water depths of 800-2000 m were undertaken to observe speci3c features identijied with the SeaMARC I sidescan system in 1983. Two dives were made in the head of Eastern Valley where pebbly mudstones ofprobable Pleistocene age were recognized outcropping on the seafloor. Constructional features of cobbles and boulders, derived by exhumation and reworking of the pebbly mudstone, were also observed. These include gravel/sand bedforms (transverse waves) on the valley floor. Slope failure features in semiconsolidated mudstone were recognized on two dives onto the St. Pierre slope. Exposures in these mudstones are rapidly eroded by intense burrowing by benthic organisms

Contourite or turbidite?: magnetic fabric of fine-grained Quaternary sediments, Nova Scotia continental rise

Samples of three piston cores and one gravity core from the Nova Scotia continental rise (depths 4210-4925 m) have been examined to differentiate parallel-to-slope and downslope depositional processes in Quaternary deposits from a region presently influenced by a strong contour current. Measurement of anisotropy of magnetic susceptibility of samples of a red-brown, silt-laminated lutite 'contourite' facies shows grain alignments which are consistent with both parallel-to-slope (contour current) flow and downslope (turbidity current) flow. We believe that these results provide support for the hypothesis that 'geologically significant' contour currents have influenced continental rise deposition during the Pleistocene. However, our observation that both alongslope and downslope alignments are present in lithologically similar units clearly demonstrates the need for studies on the relationship between lithofacies and process in this geological setting

The magnetic fabric of surficial deep-sea sediments in the HEBBLE area (Nova Scotian continental rise)

The anisotropy of magnetic susceptibility (AMS) of surficial sediments in the HEBBLE area (depth 4820 m, Nova Scotian continental rise) has been measured to study the fabric of these sediments and to relate the sediment fabric to depositional conditions. Previous investigators have established that strong but variable bottom currents are important agents in redistributing bottom sediments in the area. We observe that the upper 1.5 cm of the sediments has a primary fabric (dominantly foliar with horizontal bedding) created by bottom-current activity while sediments deeper than 2.5 cm have a predominantly secondary fabric due to bioturbation. The magnitude of the AMS signal in these sediments is generally low making it difficult to measure some of the fabric elements, especially the direction of the lineated fabric. In the upper 1.5 cm magnetic grains are predominantly oriented parallel to the regional bathymetric contours, but there is also a significant grouping of alignments perpendicular to the contours. Primary fabrics are observed in a few of the samples from the bioturbated sediments with the magnetic grains oriented parallel to the contours. Some of the variability observed between box cores in the magnetic fabric may reflect the variability of depositional conditions within the region. An analysis of the magnitude of the AMS fabric suggests that the parameter Fs, often used to denote bottom-current fabrics, is strongly dependent on the total anisotropy and only weakly dependent on the lineated nature of the fabric. Both primary and secondary fabrics can have relatively large Fs values. Thus Fs does not appear sufficient for delineating bottom current activity in the deep sea

Towards high-speed optical quantum memories

Quantum memories, capable of controllably storing and releasing a photon, are a crucial component for quantum computers and quantum communications. So far, quantum memories have operated with bandwidths that limit data rates to MHz. Here we report the coherent storage and retrieval of sub-nanosecond low intensity light pulses with spectral bandwidths exceeding 1 GHz in cesium vapor. The novel memory interaction takes place via a far off-resonant two-photon transition in which the memory bandwidth is dynamically generated by a strong control field. This allows for an increase in data rates by a factor of almost 1000 compared to existing quantum memories. The memory works with a total efficiency of 15% and its coherence is demonstrated by directly interfering the stored and retrieved pulses. Coherence times in hot atomic vapors are on the order of microsecond - the expected storage time limit for this memory.Comment: 13 pages, 5 figure

Quantum Communication

Quantum communication, and indeed quantum information in general, has changed the way we think about quantum physics. In 1984 and 1991, the first protocol for quantum cryptography and the first application of quantum non-locality, respectively, attracted a diverse field of researchers in theoretical and experimental physics, mathematics and computer science. Since then we have seen a fundamental shift in how we understand information when it is encoded in quantum systems. We review the current state of research and future directions in this new field of science with special emphasis on quantum key distribution and quantum networks.Comment: Submitted version, 8 pg (2 cols) 5 fig

Drug Resistance in Eukaryotic Microorganisms

Eukaryotic microbial pathogens are major contributors to illness and death globally. Although much of their impact can be controlled by drug therapy as with prokaryotic microorganisms, the emergence of drug resistance has threatened these treatment efforts. Here, we discuss the challenges posed by eukaryotic microbial pathogens and how these are similar to, or differ from, the challenges of prokaryotic antibiotic resistance. The therapies used for several major eukaryotic microorganisms are then detailed, and the mechanisms that they have evolved to overcome these therapies are described. The rapid emergence of resistance and the restricted pipeline of new drug therapies pose considerable risks to global health and are particularly acute in the developing world. Nonetheless, we detail how the integration of new technology, biological understanding, epidemiology and evolutionary analysis can help sustain existing therapies, anticipate the emergence of resistance or optimize the deployment of new therapies

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Bottom currents and abyssal sedimentation processes south of Iceland

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology October 1979An investigation was carried out to observe the geologic effects of steady bottom currents on sediments of East Katla Ridge on the southern insular rise of Iceland. Near-bottom southwest to west-flowing currents exceeded 20 cm sec-1 for two weeks over a 25-kilometer wide section of the ridge flank between approximately 1400 and 1800 meters water depth; maximum density and minimum temperature were observed at 1800 meters. Total transport of Iceland-Scotland Overflow Water was calculated to be 5.0 x 106 m3 sec-1; suspended sediment transport is approximately 0.4 x 106 grams sec-1, with a net deposition of 10 to 15 cm/1000 years estimated from the flux difference in and out of the station array. Sediment distribution patterns indicate that the current axis, where flow exceeds approximately 15 cm sec-1, is a site of erosion and winnowing (sand layer formation) while the current margin is a site of rapid accumulation (from observed Holocene rates of 25 to 35 cm per 1000 yr to estimated rates of greater than 100 cm/1000 yr based on 3.5 kHz echo-sounder records). Holocene silty turbidites are locally thick in a sub-marine channel; sandy turbidites and current-winnowed 'sandy contourites' are present in the axis of the major submarine canyon. ‘ Sandy contourite' deposits beneath the axis of the Iceland-Scotland Overflow Current are very poorly sorted muddy sands lacking primary sedimentary structures. Bioturbation is inferred to cause the unique characteristics of these deposits, as well as the absence of fine silt laminae in 'muddy contourites' at the current margin.Financial support for shipboard operations and most of the post-cruise data analysis was provided by NSF Grant OCE76-Sl49l to Dr. Charles Hollister. Sediment trap and hydrocast operations received partial support under ONR Contract N00014-74-C-0262

Simultaneous Operation of the Sea Beam Multibeam Echo-Sounder and the SeaMARC II Bathymetric Sidescan Sonar System

An experiment aboard the Scripps Institution of Oceanography\u27s RV Thomas Washington has demonstrated the seafloor mapping advantages to be derived from combining the high-resolution bathymetry of a multibeam echo-sounder with the sidescan acoustic imaging plus wide-swath bathymetry of a shallow-towed bathymetric sidescan sonar. To a void acoustic interference between the ship\u27s 12-kHz Sea Beam multibeam echo-sounder and the 11-12-kHz SeaMARC II bathymetric sidescan sonar system during simultaneous operations, Sea Beam transmit cycles were scheduled around SeaMARC II timing events with a sound source synchronization unit originally developed for concurrent single-channel seismic, Sea Beam, and 3.5-kHz profile operations. The scheduling algorithm implemented for Sea Beam plus SeaMARC II operations is discussed, and the initial results showing their combined seafloor mapping capabilities are presented