Oceanography Research Summary

The Oceanography Department has developed a broad research program focused on physical oceanography to meet the anticipated future needs of the Navy. Our priority basic research themes are the development of scientific capabilities to measure, analyze and forecast fields of littoral ocean variables which occur in association with synoptic/mesoscale processes over limited regional and temporal domains. The areas of emphasis include coastal and nearshore ocean dynamics, air-sea interaction phenomena and boundary currents. Regions of interest include the marginal sea ice zone, coastal ocean regions and strategic straits of the world

Using mixed methods for analysing culture : The Cultural Capital and Social Exclusion project

This paper discusses the use of material generated in a mixed method investigation into cultural tastes and practices, conducted in Britain from 2003 to 2006, which employed a survey, focus groups and household interviews. The study analysed the patterning of cultural life across a number of fields, enhancing the empirical and methodological template provided by Bourdieu’s Distinction. Here we discuss criticisms of Bourdieu emerging from subsequent studies of class, culture and taste, outline the arguments related to the use of mixed methods and present illustrative results from the analysis of these different types of data. We discuss how the combination of quantitative and qualitative methods informed our analysis of cultural life in contemporary Britain. No single method was able to shed light on all aspects of our inquiry, lending support to the view that mixing methods is the most productive strategy for the investigation of complex social phenomena

Properties of layer-by-layer vector stochastic models of force fluctuations in granular materials

We attempt to describe the stress distributions of granular packings using lattice-based layer-by-layer stochastic models that satisfy the constraints of force and torque balance and non-tensile forces at each site. The inherent asymmetry in the layer-by-layer approach appears to lead to an asymmetric force distribution, in disagreement with both experiments and general symmetry considerations. The vertical force component probability distribution is robust and in agreement with predictions of the scalar q model while the distribution of horizontal force components is qualitatively different and depends on the details of implementation.Comment: 18 pages, 12 figures (with subfigures), 1 table. Uses revtex, epsfig,subfigure, and cite. Submitted to PRE. Plots have been bitmapped. High-resolution version is available. Email [email protected] or download from http://rainbow.uchicago.edu/~mbnguyen/research/vm.htm

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset

Analysis of shared heritability in common disorders of the brain

Paroxysmal Cerebral Disorder

Rip Currents, Mega-Cusps, and Eroding Dunes

Submitted to Marine Geology 1 November 2006Dune erosion is shown to occur at the embayment of beach mega-cusps O(200m alongshore) that are associated with rip currents. The beach is the narrowest at the embayment of the mega-cusps allowing the swash of large storm waves coincident with high tides to reach the toe of the dune, to undercut the dune and to cause dune erosion. Field measurements of dune, beach, and rip current morphology are acquired along an 18 km shoreline in southern Monterey Bay, California. This section of the bay consists of a sandy shoreline backed by extensive dunes, rising to heights exceeding 40 m. There is a large increase in wave height going from small wave heights in the shadow of a headland, to the center of the bay where convergence of waves owing to refraction over the Monterey Bay submarine canyon result in larger wave heights. The large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale. The strongly refracted waves and narrow bay aperture result in near normal wave incidence, resulting in well-developed, persistent rip currents along the entire shoreline

Energetics of breaking waves within the surf zone

The article of record as published may be found at http://dx.doi.org/10.1029/JC084iC08p04931Surface elevations and velocities were measured for a variety of breaking wave conditions including collapsing, plunging, and spilling breakers. Turbulent and wave-induced velocity components are separated by associating the wave-induced velocities with contribution coherent with the surface. Most of the measurements were made in the lower half of the water column and are indicative of conditions in this region. The average velocity intensity for all experiments was 85% wave induced, indicating that the kinetic energy is primarily wave induced. Remarkably little difference was found between collapsing, plunging, and spilling breakers in terms of percent wave-induced velocity intensity. Breaking waves can be characterized as highly nonlinear with strong wave-wave interactions resulting in energy being transferred away from the primary wave frequency, resulting in a saturation region at higher frequencies. Similarity arguments assuming kinematic instability with phase speed the only relevant parameter suggest a -3 slope for the log-log frequency spectrum of both the surface and horizontal velocities in shallow water. The surface elevation spectra of collapsing and plunging breakers have a slope more closely approximated by a -7/3 slope, indicating the possible importance of surface tension in the breaking processes: the velocity spectra show a -3 slope. The saturation region for spilling breakers surfaces elevation spectra varied from -3 at lower frequencies to -5 at highest frequencies

Modelling infragravity motions on a rip-channel beach

The article of record as published may be located at http://dx.doi.org/10.1016/j.coastaleng.2005.10.010A non-linear shallow water wave model operating on the time-scale of wave groups is compared with measurements of infragravity motions on a rip-channel beach to verify the model concepts and assess the model performance. The measurements were obtained during the RIP-current EXperiment (RIPEX) in concert with the Steep Beach Experiment (SBE) performed at Sand City, Monterey Bay, CA, during the spring of 2001. The nearshore bathymetry was made up of shore-connected shoals incised by relatively narrow rip-channels spaced approximately 125 m apart. The comparison considers a 20-day period during which significant changes in both the offshore wave climate and nearshore bathymetry occurred. The temporal variation in infragravity conditions during the experiment is strong, with computational results typically explaining 70% to 80% of the observed infragravity motions within the nearshore. In contrast to the temporal variation, the alongshore spatial variation in infragravity intensity during the experiment is generally weak, even though the underlying bathymetry shows strong depth variations. Model computations suggest preferential coupling between the computed edge wave motions and the quasi-periodic bathymetry is present, a prerequisite for strong spatial variability. However, the infragravity field is dominated by cross-shore infragravity motions, which are only weakly coupled to the quasiperiodic bathymetry, resulting in a weak alongshore variability of the total infragravity motions.The Steep Beach Experiment and EBT and TPS were funded by the Office of Naval Research, Coastal Science Program, under contract N00014-01-WR-20023. JM was funded by the Florida Sea Grant Program. Part of the work presented here was done while AR held a National Research Council-NPS Research Associateship funded through the National Ocean Partnership Program (NOPP) under contract N0001463WR20191 and the Office of Naval Research under contract N00014-01- WR20023. Part of this material is based upon work funded by the National Science Foundation under grant 0136882. Additional funding from the Dutch National Science Foundation, contract DCB.5856 is much appreciated

Energy saturation and phase speeds measured on a natural beach

The article of record as published may be found at http://dx.doi.org/10.1029/JC087iC12p09499Field measurements of wave height and speed from 7-m depth shoreward are described. The experiment plan consisted of a shore-normal transect of closely spaced (compared to a dominant wave length) velocity, pressure, and elevation sensors on an almost plane profile having an inshore slope of 1:50. As the waves shoal and begin to break, the dominant dissipative mechanism is due to turbulence generated at the crest, and wave heights become increasingly depth controlled as they progress across the surf zone. Wave heights in the inner surf zone are strongly depth independent: the envelope of the wave heights is described by H/sub rms/ = 0.42 h. The depth dependence of the breaking wave height is shown to be related to the kinematic instability criterion. Celerity spectra were measured by using phase spectra calculated between pairs of adjacent sensors. Inshore of 4-m depth, the celerity was found distant over the energetic region of the spectrum. A 'mean' celerity was compared with linear theory and was within +20% and -10%, showing good agreement for such a nonlinear, dissipative region

Steep Beach and RIPEX experiment

The Ocean Turbulence Laboratory in the Oceanography Department at the Naval Postgraduate School has an active research program addressing a range of ocean turbulent boundary layer problems. The group has developed observational systems for studying sub-ice boundary layers in polar regions, coastal internal waves, solitons and turbulence over the continental shelf, and the wave forced boundary bottom boundary layer over the inner shelf and surf zone.Wave dissipation due to bottom friction can be the dominant mechanism transforming waves across the shelf during times of significant waves. During our participation in the Shoaling Waves DRI, we will make measurements of wave dissipation due to bottom friction in collaboration with other wave transformation studies in October 1999 at a site approximately 2km offshore from the Army Corps of Engineers field research facility at Duck, North Carolina