Detection of mRNA sequences homologous to the human glutathione peroxidase and rat cytochrome P-450IVA1 genes in Mytilus edulis

In this study we have used cloned gene probes for human glutathione peroxidase (GPX), rat cytochrome P-450IVA1 and rat cytochrome P-450IIE1 to detect homologous sequences in RNA from the hepato-pancreas of Mytilus edulis. The presence of sequences hybridising to the GPX and P-450IVA1 probes, but not to the P-450IIE1 probe, confirms the ancient origin of the former genes and indicates that conserved-sequence DNA probes from higher organisms can be used to examine the structure and function of genes of environmental interest in marine organisms.     

Structure and Stability of Non-Transform Discontinuities on the Mid-Atlantic Ridge between 24° N and 30° N

Observations of the median valley within the 24–30° N area ofthe Mid-Atlantic Ridge (MAR), using the IOSDL high resolutionside-scan sonar instrument TOBI, image four separate areas of themedian valley, containing part or all of nine spreading segments, and fivenon-transform discontinuities between spreading segments (NTDs).These high resolution side scan images were interpreted in parallel withmultibeam bathymetry (Purdy et al., 1990), giving a greater degree ofstructural precision than is possible with the multibeam data alone. Threedistinct types of NTD were identified, corresponding in part to typespreviously identified from the multibeam bathymetric survey of the area.Type 1 NTDs are termed septal offsets, and are marked by a topographic ridgeseparating the two spreading segments. The offset between the spreadingsegments ranges from 9 to 14 km. These can be further subdivided into Type1A in which the septa run parallel to the overall trend of the MAR and Type1B in which the septa lie at a high angle to the bulk ridge trend. Type 1ANTDs are characterised by overlap of the neovolcanic zones of the segmentson each side, and strong offaxis traces, while Type 1B NTDs show no overlapof neovolcanic zones, and weak offaxis traces. Type 2 NTDs arebrittle/ductile extensional shear zones, marked by oblique extensionalfractures, and associated with rotation of tectonic and volcanic structuresaway from the overall trend of the MAR. Type 3 NTDs are associated withoffsets of less than 5 km, and show no sign of any accommodating structure.In this type of NTD, the offset zone is covered with undeformed volcanics.The type of NTD developed at any locality along the ridge axis appears todepend on the amount of segment offset and segment overlap, the overalltrend of the mid-ocean ridge, the width of the zone of discontinuity, themedian valley offset and the longevity of the offset. These factorsinfluence the mechanical properties of the lithosphere across thediscontinuity, and ultimately the tectonic style of the NTD that can besupported. Thus brittle/ductile extensional shear zones are long-livedstructures favoured by large segment offsets, and small or negative segmentoverlaps. Septa can be short or long lived, and are associated with largesegment offsets. Segment overlaps vary from negative (an along axis gap) tozero, for Type 1B septal offsets, or positive to zero for Type 1A septaloffsets. Non-tectonised NTDs are generally short lived structures,characterised by small segment offsets and zero or positive overlaps.     

Modelling of run up of steep non-breaking waves

A Navier–Stokes solver is used to examine steep waves as they run up a steep beach (10.54°). The volume of fluid method (VOF) is used to model the free surface. Comparison with experimental results shows reasonable overall agreement in the prediction of the free-surface, velocities and accelerations within the flow. A spurious feature at the free-surface was found which does reduce the quality of the results. For a steep wave we see the transition from a steep wave front to a smooth run-up tongue at the beach that is in qualitative agreement with experiment.     

The Black Band Disease of Atlantic Reef Corals.

Abstract. The cyanophyte (Cyanobaclerium) that causes black band disease of Atlantic reef corals is described under the name Phormidium corallyticum , new species (family Oscillatoriaceae) , and its generic placement is discussed from the standpoint of the GEITLERian (classical) and D rouet systems. Distinguishing characters include densely interwoven filaments that form a blackish mat and trichomes without significant cell wall constrictions, almost isodiametric cells (4.2 μm mean width, 4.0μm mean length) tapering end cells, and thin (0.1 μm or less) mucilaginous wall coating. Transmission electron microscopy shows typical cyanophyte cell walls, sheath, nucleoplasm, and cytoplasmic inclusions, but an unusual thylakoid of straight, and, as seen in cell cross section, radiating lamellae. The dark coloration is due to a high concentration of phycocyanin and some phycoerythrin. The species is similar to Oscillatoria (= Phormidium) submembranacea , which differs in several morphological features and does not infect coral tissue. It is concluded that Phormidium should be used for this and related species that have external mucilage but not the distinct sheath found in Lyngbya.     

Fault scarp identification in side-scan sonar and bathymetry images from the Mid-Atlantic Ridge using wavelet-based digital filters

Digital filters designed using wavelet theory are applied to high resolution deep-towed side-scan sonar data from the median valley walls, crestal mountains, and flanks of the Mid-Atlantic Ridge at 29°10 N. With proper tuning, the digital filters are able to identify the location, orientation, length, and width of highly reflective linear features in sonar images. These features are presumed to represent the acoustic backscatter from axis-facing normal faults. The fault locations obtained from the digital filters are well correlated with visual geologic interpretation of the images. The side-scan sonar images are also compared with swath bathymetry from the same area. The digitally filtered bathymetry images contain nine of the eleven faults identified by eye in the detailed geologic interpretation of the side-scan data. Faults with widths (measured perpendicular to their strike) of less than about 150 m are missed in the bathymetry analysis due to the coarser resolution of these data. This digital image processing technique demonstrates the potential of wavelet-based analysis to reduce subjectivity and labor involved in mapping and analyzing topographic features in side-scan sonar and bathymetric image data.     

Cadmium, copper, and zinc interactions with marine humus as a function of ligand structure

The interactions in seawater of cadmium, copper, and zinc with natural levels of marine humus (fulvic and humic acids) were studied using differential pulse anodic stripping voltammetry (DPASV). Interactions with Cu were also examined by ultraviolet spectrophotometry. The degree of interaction relates to the structure of the particular fulvic or humic acid tested. Marine fulvic and humic acids with different equivalent weights and varying degrees of aromaticity and heteroatom substitution were tested to assess the relative importance of these fundamental structural features in determining the degree of interaction. An index of heteroatom substitution, derived from proton magnetic resonance spectra of these materials, when combined with equivalent weights correlated with the nature and degree of metal interaction. Both marine fulvic and humic acids appreciably interacted with Zn. In contrast, the extent of interaction of fulvic acids with Cu appears to be related to their structure while humic acids appear to interact with Cu regardless of structure. Cadmium interacts only with mature, highly crosslinked humic acids.     

Applying a science-forward approach to groundwater regulatory design

Hydrogeology Journal - Groundwater sustainability is challenged by the difference between legal and scientific understanding of groundwater, as well as the lack of focused attention to regulatory...     

Microvertebrates from the Rhaetian basal bone bed of Saltford,near Bath,SW England

The famous Rhaetian bone bed (Late Triassic, 205 Ma) is well known because it marks a major switch in depositional environment from terrestrial red beds to fully marine conditions throughout the UK and much of Europe. The bone bed is generally cemented and less than 10 cm thick. However, we report here an unusual case from Saltford, near Bath, S.W. England where the bone bed is unconsolidated and up to nearly 1 m thick. The exposure of the basal beds of the Westbury Formation, Penarth Group includes a bone bed containing a diverse Rhaetian marine microvertebrate fauna dominated by sharks, actinopterygian fishes and reptiles. Despite the unusual sedimentary character of the bone bed, we find similar proportions of taxa as in other basal Rhaetian bone beds (55–59 % Lissodus teeth, 13–16 % Rhomphaiodon teeth, 12–14 % Severnichthys teeth, 6–9% Gyrolepis teeth, 3–4% undetermined sharks’ teeth, 1–3% undetermined bony fish teeth, and < 1% of each of Hybodus, Parascylloides, and Sargodon), the only differences being in the proportions of Rhomphaiodon teeth, which can represent 30–40 % of specimens elsewhere. This suggests that taphonomic bias of varying Rhaetian bone beds may be comparable despite different sedimentary settings, and that the proportions of taxa say something about their original proportions in the ecosystem.     

Titan solar occultation observed by Cassini/VIMS: Gas absorption and constraints on aerosol composition

A solar occultation by Titan's atmosphere has been observed through the solar port of the Cassini/VIMS instrument on January 15th, 2006. Transmission spectra acquired during solar egress probe the atmosphere in the altitude range 70 to 900 km at the latitude of 71° S. Several molecular absorption bands of CH₄ and CO are visible in these data. A line-by-line radiative transfer calculation in spherical geometry is used to model three methane bands (1.7, 2.3, 3.3 μm) and the CO 4.7 μm band. Above 200 km, the methane 2.3 μm band is well fit with constant mixing ratio between 1.4 and 1.7%, in agreement with in situ and other Cassini measurements. Under 200 km, there are discrepancies between models and observations that are yet fully understood. Under 480 km, the 3.3 μm CH₄ band is mixed with a large and deep additional absorption. It corresponds to the C-H stretching mode of aliphatic hydrocarbon chains attached to large organic molecules. The CO 4.7 μm band is observed in the lower stratosphere (altitudes below 150 km) and is well fit with a model with constant mixing ratio of 33±10 ppm. The continuum level of the observed transmission spectra provides new constraints on the aerosol content of the atmosphere. A model using fractal aggregates and optical properties of tholins produced by Khare et al. [Khare, B.N., Sagan, C., Arakawa, E.T., Suits, F., Callcott, T.A., Williams, M.W., 1984. Icarus 60, 127-137] is developed. Fractal aggregates with more than 1000 spheres of radius 0.05 μm are needed to fit the data. Clear differences in the chemical composition are revealed between tholins and actual haze particles. Extinction and density profiles are also retrieved using an inversion of the continuum values. An exponential increase of the haze number density is observed under 420 km with a typical scale height of 60 km.