Shockwaves in converging geometries

Plate impact experiments are a powerful tool in equation of state (EOS) development, but are inherently limited by the range of impact velocities accessible to the gun. In an effort to dramatically increase the range of pressures which can be studied with available impact velocities, a new experimental technique is being developed. The possibility of using a confined converging target to focus Shockwaves and produce a large amplitude pressure pulse is examined. When the planar shock resulting from impact enters the converging target the impedance mismatch at the boundary of the confinement produces reflected Mach waves and the subsequent wave interactions produce a diffraction cycle resulting in increases in the shock strength with each cycle. Since this configuration is limited to relatively low impedance targets, a second technique is proposed in which the target is two concentric cylinders designed such that the inner cylinder will have a lower shock velocity than the much larger shock velocity in the outer cylinder. The resulting dispersion in the wave front creates converging shocks, which will interact and eventually result in a steady Mach configuration with an increase in pressure in the Mach disk. Numerical simulations indicate a significant increase in pressure for both methods and show promise for the proposed concepts

Laboratory spectroscopy in support of atmospheric measurements

Optical measurements of trace species in the atmosphere require precise, accurate spectroscopic data for the molecules under study. This laboratory exits to provide high quality spectroscopic data for the interpretation of data from existing satellite, balloon, ground, and aircraft instruments, as well as to provide sufficient data to assess the feasibility of new instruments

Ground-based lidar measurements of stratospheric ozone. The NASA/GSFC stratospheric ozone lidar trailer experiment STROZ LITE

The major research objective is the measurement of high precision vertical profiles of ozone between 20-40 kilometers. The precision is such that the instrument should be capable of detecting a small trend (on the order of less that 1 percent per year) over a 5-10 year period. Temperature was measured between 30 and 365 km. The Goddard Space Flight Center (GSFC) mobile lidar was installed at Table Mountain and a comparison between it and the permanent Jet Propulsion Laboratory (JPL) lidar was made over the course of about 3 weeks. The lidars agreed very well between 20 and 40 km, and under certain conditions up to 45-47 km. There were several anomalies that both lidars followed very well. Agreement with Rocket Ozonesonde (ROCOZ) and electrochemical concentration cell (ECC) sondes was also very good

Integration of technologies for understanding the functional relationship between reef habitat and fish growth and production

Functional linkage between reef habitat quality and fish growth and production has remained elusive. Most current research is focused on correlative relationships between a general habitat type and presence/absence of a species, an index of species abundance, or species diversity. Such descriptive information largely ignores how reef attributes regulate reef fish abundance (density-dependent habitat selection), trophic interactions, and physiological performance (growth and condition). To determine the functional relationship between habitat quality, fish abundance, trophic interactions, and physiological performance, we are using an experimental reef system in the northeastern Gulf of Mexico where we apply advanced sensor and biochemical technologies. Our study site controls for reef attributes (size, cavity space, and reef mosaics) and focuses on the processes that regulate gag grouper (Mycteroperca microlepis) abundance, behavior and performance (growth and condition), and the availability of their pelagic prey. We combine mobile and fixed-active (fisheries) acoustics, passive acoustics, video cameras, and advanced biochemical techniques. Fisheries acoustics quantifies the abundance of pelagic prey fishes associated with the reefs and their behavior. Passive acoustics and video allow direct observation of gag and prey fish behavior and the acoustic environment, and provide a direct visual for the interpretation of fixed fisheries acoustics measurements. New application of biochemical techniques, such as Electron Transport System (ETS) assay, allow the in situ measurement of metabolic expenditure of gag and relates this back to reef attributes, gag behavior, and prey fish availability. Here, we provide an overview of our integrated technological approach for understanding and quantifying the functional relationship between reef habitat quality and one element of production – gag grouper growth on shallow coastal reefs

Brief \u3cem\u3eAmicus Curiae\u3c/em\u3e of Environmental Defense Fund, National Audubon Society, National Wildlife Federation, Natural Resources Defense Council, Sierra Club, and Defenders of Wildlife, \u3cem\u3eTVA v. Hill\u3c/em\u3e, No. 76-1701

Brief for the respondents in the case of Tennessee Valley Authority v. Hiram G. Hill Jr., et al., heard by the United States Supreme Court in the October Term of 1977

Advances in Shock Compression of Mantle Materials and Implications

Hugoniots of lower mantle mineral compositions are sensitive to the conditions where they cross phase boundaries including both polymorphic phase transitions and partial to complete melting. For SiO_2, the Hugoniot of fused silica passes from stishovite to partial melt (73 GPa, 4600 K) whereas the Hugoniot of crystal quartz passes from CaCi_2 structure to partial melt (116 GPa, 4900 K). For Mg_2SiO_4, the forsterite Hugoniot passes from the periclase +MgSiO_3 (perovskite) assemblage to melt before 152 GPa and 4300 K, whereas the wadsleyite Hugoniot transforms first to periclase +MgSiO_3 (post-perovskite) and then melts at 151 GPa and 4160 K. Shock states achieved from crystal enstatite are molten above 160 GPa. High-pressure Grüneisen parameters for molten states of MgSiO_3 and Mg_2SiO_4 increase markedly with compression, going from 0.5 to 1.6 over the 0 to 135 GPa range. This gives rise to a very large (>2000 K) isentropic rise in temperature with depth in thermal models of a primordial deep magma ocean within the Earth. These magma ocean isentropes lead to models that have crystallization initiating at mid-lower mantle depths. Such models are consistent with the suggestion that the present ultra-low velocity zones, at the base of the lowermost mantle, represent a dynamically stable, partially molten remnant of the primordial magma ocean. The new shock melting data for silicates support a model of the primordial magma ocean that is concordant with the Berkeley-Caltech iron core model [1] for the temperature at the center of the Earth

Shock temperatures of preheated MgO

Shock temperature measurements via optical pyrometry are being conducted on single-crystal MgO preheated before compression to 1905–1924 K. Planar shocks were generated by impacting hot Mo(driver plate)-MgO targets with Mo or Ta flyers launched by the Caltech two-stage light-gas gun up to 6.6 km/s. Quasi-brightness temperature was measured with 2–3% uncertainty by a 6-channel optical pyrometer with 3 ns time resolution, over 500–900 nm spectral range. A high-power, coiled irradiance standard lamp was adopted for spectral radiance calibration accurate to 5%. In our experiments, shock pressure in MgO ranged from 102 to 203 GPa and the corresponding temperature varied from 3.78 to 6.53 kK. For the same particle velocity, preheated MgO Hugoniot has about 3% lower shock velocity than the room temperature Hugoniot. Although model shock temperatures calculated for the solid phase exceeded our measurements by ~5 times the uncertainty, there was no clear evidence of MgO melting, up to the highest compression achieved

Setting the foundation for renewal: restoring sponge communities aids the ecological recovery of Florida Bay

Coastal ecosystems are constantly buffeted by anthropogenic forces that degrade habitats and alter ecological processes and functions; in turn, this habitat degradation diminishes the ecosystem goods and services on which humans rely. Within the last few decades, the field of restoration ecology has burgeoned into a discipline that marries scientific rigor with functional restoration practice—an idea championed by Pete Peterson and his research. Here, we describe our efforts to restore the hard-bottom sponge communities of Florida Bay, FL (USA)—a once-diverse subtropical lagoon severely degraded by cyanobacteria blooms—and the scientific and practical lessons learned from those efforts. Sponge community restoration yielded insights into basic sponge biology and ecology (e.g., density-dependent growth rates) and hastened the recovery of ecological processes (e.g., rates of sedimentation, structuring of water column characteristics, soundscape productions). Because the results of our initial restoration efforts were promising, our collaboration among academic researchers, natural resource managers, and non-governmental organizations has begun scaling up restoration efforts to re-establish the sponge communities over large areas of degraded hard-bottom to “jump start” the ecological recovery of Florida Bay. Though our efforts show promise for ecological recovery, restoration will require a concerted effort by scientists, resource managers, and citizens to stem the anthropogenic drivers of ecological degradation of this unique South Florida ecosystem

Factors Regulating Settlement and Microhabitat Use by Spiny Lobsters Panulirus argus

Clumps of highly-branched red algae Laurencia spp. serve as important settling habitat for postlarval spiny lobsters Panulirus argus and as residence for early benthic-stage juveniles. Given choice between the 2 most abundant macrophytes in Florida Bay, Laurencia spp. and the seagrass Thalassia testudinum, postlarval and juvenile lobsters chose Laurencia spp. Postlarvae apparently use intricate algal architecture as a cue for settlement, whereas juveniles use both architecture and food abundance in selecting habitat. In tethering experiments, predation on juvenile lobsters was very high on open sand, much reduced in algal clumps and seagrass, and lowest in dense algal meadows. Predation rates were similar day and night both on open sand and in vegetation. Most lobsters vacated algal clumps located within continuous algal meadows overnight, at a rate significantly higher than that from isolated algal clumps. We suggest that algal clump distribution, postlarval settling behavior, and juvenile interpatch movement and mortality contribute to the highly dispersed distribution and locally sparse abundances of early benthic juveniles