Recent EES Division Highlights

Other Archived Highlights

September 24, 2008

Analysis of a Crater-Forming Meteorite Impact in Peru

Douglas ReVelle (EES-2) and collaborators analyzed the fireball that produced a crater-forming meteorite fall near Carancas, Peru, on 15 September 2007. The researchers used eyewitness, seismic, and infrasound records to investigate the fireball and crater. Several eyewitnesses described the fireball as being nearly as bright as the sun and heard a loud explosion. Although the fall of the meteorite was not recorded optically, global instrumentation provided by the International Monitoring System of the Comprehensive Test Ban Treaty Organization recorded infrasound waves produced by the fireball passage. The meteorite impact, which produced a crater of 13.5 m diameter, released on the order of 1010 J of energy, equivalent to 2-3 tons of TNT high explosives. The scientists calculate the initial mass of the meteoroid to be in the range of 3-9 tons. Their modeling suggests a final end mass for impact on the order a few metric tons and an impact velocity in the 1.5-4 km/s range.

The crater 7 days after formation.

The most unusual aspect of this crater-forming impact is the nature of the impactor. In general, chondritic (stony) meteorites break up during atmospheric flight and do not reach the surface as large objects with a significant fraction of their pre-atmospheric speed. The scientists conclude that a strong, coherent stony object with few shock cracks could withstand the pressures most of their models predict for the meteorite (based on lab measurements of meteorite strengths) and experience mild or no fragmentation as opposed to the catastrophic fragmentation typical for chondrites.

The researchers deduce that the formation of such a substantial crater from a chondritic mass was the result of the unusually high strength (and corresponding low degree of fragmentation in the atmosphere) of the meteoritic body. Additionally, the high altitude of the impact site resulted in an almost one order of magnitude higher impact speed than would have been the case for the same body impacting close to sea level. Modeling suggests that much of the mass of the original impactor spalled out of the crater and/or the mass remaining in the crater is in disaggregated small fragments.

Reference: Brown, P., D. O. ReVelle, E. A. Silber, W. N. Edwards, S. Arrowsmith, L. E. Jackson Jr., G. Tancredi, and D. Eaton "Analysis of a Crater-Forming Meteorite Impact in Peru", Journal of Geophysical Research 113, E09007, (2008).

September 15, 2008

Nonlinear Elastic Wave Spectroscopy in Nondestructive Evaluation

Paul Johnson (EES-11) was asked to organize a special session, "Nonlinear Elastic Wave Spectroscopy in Nondestructive Evaluation", at the 2009 International Congress on Ultrasonics (ICU) in Santiago, Chile, January 9-17. The ICU was formed from a merger of the World Congress on Ultrasonics and Ultrasonics International. The conference offers the scientific and engineering community working in the field of ultrasonics an excellent opportunity for exchange between scientists from industry academia, government, and suppliers of ultrasound equipment.

September 10, 2008

Hybrid Process and System Model Assesses Geologic CO₂ Sequestration

Geologic sequestration is a promising technology to mitigate the impact of anthropogenic CO₂ emissions. Assessment of long-term viability of CO₂ storage is a complex function of CO2-reservoir interactions, leakage pathways, and risks. It requires integrating theory, field observation, experiment and simulation over a wide range of spatial and temporal scales, all of which involve substantial uncertainties. Because a detailed model that incorporates all of the underlying processes is not computationally feasible, a methodology is needed that abstracts these processes into a manageable, system-level model that is robust enough to apply to a wide variety of potential sequestration sites.

LANL scientists developed a hybrid process and system level model, CO2-PENS (Predicting Engineered Natural Systems), to investigate the long-term fate of CO₂ in geologic reservoirs. CO2-PENS uses a science-based-prediction approach by integrating information from process-level laboratory experiments, field experiments/observations, and process-level numerical modeling. The modular structure of CO2-PENS permits individual, interacting process models to contain detailed physics yet remain computationally efficient. It provides insights into the emergent behavior of aggregate processes that could not be obtained by using individual process models. CO2-PENS is being applied to several sequestration field tests in order to investigate the feasibility of deploying geologic sequestration technology while accounting for processes such as wellbore leakage, groundwater, atmospheric impacts and economic impacts. The ultimate goal is to use CO2-PENS as a screening tool for the suitability of sequestration sites and as an assessment tool for determining performance of individual sites.

(a) Schematic of wellbore leakage processes and (b) samples from SACROC core showing interactions with CO2.
The orange zone in the cement indicates reaction with CO₂.

In the current sequestration scenario, researchers used CO2-PENS to examine the fate of CO₂ via wellbore release and the resulting impact of CO₂ to a shallow aquifer and release to the atmosphere. CO2-enhanced oil recovery operations provide a CO₂ sequestration analog with a multidecade history of CO₂ operations. The scientists used observations from a recent study of wellbore cements at Scurry Area Capital Reef Operations Committee (SACROC) in Texas to obtain geologic and wellbore data to incorporate into a synthetic, depleted oil reservoir the CO2-PENS model (Figure 2). This research demonstrated the utility of linking the two embedded process modules (wellbore leakage and atmospheric impact), which have significantly different physics, and determining their interaction. For the study's hypothetical example, the predicted leakage resulted in small discrete plumes in close proximity to leaking wells as well as very small changes in local atmospheric CO₂ concentrations. The results (below) predict that CO₂ leakage from wellbores is much smaller than the proposed limit of 0.01% per year for the site.

The average (dotted line), 1 standard deviation (light green), 2 standard deviation (darker green), and 3 standard deviation (dark green) CO₂ accumulations calculated for 1000 simulations of a 50 year injection period. (a) Amount of CO₂ accumulating in the top permeable layer due to wellbore leakage, (b) amount of CO₂ accumulating in the middle permeable layer due to wellbore leakage, and (c) amount of CO₂ accumulating in the sequestration reservoir (the sum of quantity injected minus amount released through wellbores).

Researchers included H.S. Viswanathan (EES-6), R.J. Pawar, P.H. Stauffer, J.P. Kaszuba, J.W. Carey, and S.C. Olsen (EES-6); G.N. Keating (EES-9); D. Kavetski (University of Newcastle, Australia); and G.D. Guthrie (SPO). Reference: "Development of a Hybrid Process and System Model for the Assessment of Wellbore Leakage at a Geologic CO₂ Sequestration Site", Environmental Science and Technology, in press. The DOE Zero Emission Research and Technology (ZERT) Program supported the work.

August 25, 2008

Role of Iron in Aging of Polysiloxane Foams

Chemical degradation of room temperature vulcanized polysiloxane filled foams is an important issue because it can strongly affect mechanical properties and long-term service of these materials. The foams are subject to degradation as a result of aging and environmental conditions. Although these foams generally show low reactivity with oxygen, sunlight, and most chemicals, hydrolysis of the foams in trace amounts of water is a potential concern. While these foams are not hygroscopic, fillers used to reinforce them can absorb water.

Michael Blair (EES-2), Ross Muenchausen (MST-8), Dean Taylor (MPA-10), Andrea Labouriau (MST-7), Wayne Cooke (MST-8, retired), and Tom Stephens (WT-6) conducted electron paramagnetic resonance and Mössbauer spectroscopy to investigate potential aging mechanisms in these filled polysiloxane foams, diatomaceous earth filler, and their other constituents.

EPR spectra, measured at room temperature, of lepidocrocite that has been step-annealed to the specified temperature. The EPR spectrum of Celite® 350 (diatomaceous earth) has also been shown for comparison, and it is clear that annealed lepidocrocite is present in diatomaceous earth.

These materials are used as stress cushions, and the presence and role of water is particularly important. The study found the presence of intermediate forms of iron oxides in diatomaceous earth fillers and polysiloxane foams indicating that the diatomaceous earth is a marker for the water content rather than directly participating in water cycling in the foams.

The Non-Nuclear Enhanced Surveillance program supported the work. Reference: "EPR and Mössbauer Characterization of RTV Polysiloxane Foams and their Constituents" in Polymer Stability and Degradation 93, 1585-1589 (2008).

Award for Integrating Scientific Data into Yucca Mountain License Application

Douglas Weaver (EES-7) was one of the SNL 15-member team recipients to receive a Sandia National Laboratories Recognition Award for integrating 20-plus years of scientific data into the License Application for the proposed Yucca Mountain Waste Repository. SNL is the DOE Office of Civilian and Radioactive Waste Management Lead Laboratory for Repository Systems. The lead laboratory is responsible for producing a sound technical basis and defensible Nuclear Regulatory Commission (NRC) license application for the world's first geologic repository for the disposal of high-level radioactive waste and spent nuclear fuel. The lead lab team completed nearly four years of technically challenging work in less than two years, meeting DOE's commitment to Congress and the Nation to submit a license application for Yucca Mountain on or before June 30, 2008.

August 11, 2008

Flow Cytometry Examination of Immune Function in Poultry

Jeanne Fair (EES-2), Kirsten Taylor-McCabe, Yulin Shou, and Babs Marrone (all of B-7) applied the LANL flow cytometry resources to the immunophenotyping of chickens. Immunophenotyping is a process used to identify cells based on the types of antigens or markers on the surface of the cell. Investigations on the immune response in birds relative to disease resistance and infection is important to the understanding of diseases in the environment and our agricultural resources.

The work demonstrates that flow cytometry can be used to identify the cell surface molecules (CD or "cluster of differentiation" molecules) that are expressed on white blood cells or lymphocytes. These molecules indicate the different stages of activation of the lymphocytes aiding in a more complete understanding of the overall immune function. The scientists examined the reliability of using these methods to compare chickens raised in different environments and conditions and the reproducibility of the method between commercially available antibodies and labeling reagents.

This paper is the first in a series of reports describing lymphocyte subpopulations in birds that included a collaboration of a West Nile virus infection study at Colorado State University last fall. This project was assisted by the expertise of Charles Hathcock and David Keller (both in ENV-EAQ). The research, "Immunophenotyping of Chicken Peripheral Blood Lymphocyte Subpopulations: Individual Variability and Repeatability", is in press in Veterinary Immunology and Immunopathology, doi:10.1016/j.vetimm.2008.05.012. LDRD supported the research.

August 6, 2008

Research on Discharge Physics on Other Planets Published in Space Science Review

Robert Roussel-Dupre, Jonah Colman, and Eugene Symbalisty of EES-2 and collaborators D. Sentman (University of Alaska Fairbanks) and V.P. Paska (Pennsylvania State University) published an overview of discharge physics including both conventional and runaway breakdown in atmospheres. The paper discusses transient luminous events and terrestrial gamma-ray flashes in the context of discharge processes on other planets.

The acceleration, scattering, and energy loss or gain experienced by an electron as it moves through a gas subject to an applied electric field depends entirely on the gas composition, the details of the electron interactions with the constituent particles, and the boundary conditions. For weak fields the electrons drift and diffuse through the gas while undergoing elastic and inelastic collisions that together with the field define their momentum and energy distribution. The inelastic interactions that can occur include rotational, vibrational, and electronic excitations of the gas particles as well as losses from attachment and recombination. For stronger fields it is possible for ionizing collisions to take place. A gas discharge is initiated when the applied electric field exceeds the threshold value necessary for a sufficient population of electrons to overcome collisional drag and accelerate to energies beyond the gas ionization potential. In addition the ionization rate must exceed the net dissociative attachment rate (if extant) in order to have a net growth in the electron population. The energy or electric field at which the two balance each other defines the threshold for a discharge to initiate. Three-body attachment may also play an essential role in defining the overall development of the discharge as in air.

Two electrical breakdown mechanisms are known to operate in dielectrics. The conventional breakdown process is recognized as the sparks, arcs, and glow discharges of routine occurrence. The second is a relatively new mechanism called runaway breakdown, involves an avalanche of relativistic electrons that are collimated by the applied field to form an electron beam. Runaway breakdown may play an important role in lightning discharges on Earth.

The authors examine the kinetic theory of electron transport in gases relevant to planetary atmospheres (nitrogen, oxygen, hydrogen, carbon dioxide, methane, and helium) and present results of detailed Boltzmann kinetic calculations for a range of applied electric fields. These calculations are compared with experimental discharge swarm data.

Of the many forms that a discharge can take in the terrestrial environment, lightning is by far the most spectacular and the most dangerous. The amount of energy expended in a single event is generally more than gigajoules with power levels reaching tens to hundreds of gigawatts. The currents that flow in a cloud-to-ground (CG) discharge range in magnitude from hundreds of amps to hundreds of kiloamps and transfer Coulombs to tens of Coulombs of charge. The bulk of this electrical energy flows through small cross-sectional areas with radii ranging from centimeters to tens of centimeters and over long distances extending to many kilometers. The kinetic energy density in lightning is sufficient in many cases to heat the air to tens of thousands of degrees Kelvin and to generate acoustic shock waves that can be heard out to tens of kilometers. Terrestrial lightning is easily observed from the ground and from space in the optical, the radio frequency, and most recently in the X-ray and gamma ray parts of the electromagnetic spectrum. Some of the physical manifestations of the lightning discharge are shown in Figure 1.

The scientists conclude that the precise manner in which an electrical discharge would evolve on a given planet depends on the magnitude and atmospheric profile of the electric fields. The charging mechanisms and the gas density profile are crucial to establishing the conditions that are conducive to gas breakdown. The researchers conclude that under similar conditions runaway breakdown is more likely to occur on the gas giants such as Jupiter than conventional breakdown when compared to Earth or the other planets. Radiofrequency and gamma-ray emissions from the runaway beam would be highly collimated on the gas giants.

Reference: R. Roussel-Dupré, J. J. Colman, E. Symbalisty, D. Sentman, V.P. Pasko, "Physical Processes Related to Discharges in Planetary Atmospheres", Space Science Review, June 2008; DOI 10.1007/s11214-008-9385-5.

Thirteen lightning-related transient luminous events. Several types of these events are known and shown here: relatively slow-moving fountains of blue light known as 'blue jets' which emanate from the top of thunderclouds up to an altitude of 40 km, 'sprites' that develop at the base of the ionosphere and move rapidly downwards at speeds up to 10 000 km s-1, 'elves' which are lightning induced flashes that can spread over 300 km laterally, and upward moving 'gigantic jets' which establish a direct path of electrical contact between thundercloud tops and the lower ionosphere.

August 4, 2008

Invited Talk on Panophosphors

Michael Blair (EES-2) gave an invited talk, "Luminescence and Structural Properties of Nanophosphors," at the 3rd International Conference on Optical, Optoelectronic, and Photonic Materials and Applications in Edmonton, Canada. The presentation highlighted recent work on nanophosphor materials performed in collaboration with MST-8 (Ross Muenchausen, Luiz Jacobsohn, Bryan Bennett, and Stephanie Tornga), N-1 (Ed McKigney, Minesh Bacrania, Ernst Esch, Sy Stange), MST-7 (Rob Gilbertson, Debra Wrobleski), MPA-MC (Rico Del Sesto, Denisse Ortiz-Acosta), and Oklahoma State University (E. Yukihara).

The talk was an overview of recent work in the area of fundamental science of insulators in the nanoscale regime or nanophosphors. The optical and structural properties of two classes of phosphors (scintillating oxyorthosilicates and Al₂O₃ storage phosphors) were studied through the use of x-ray diffraction, transmission electron microscopy, electron paramagnetic resonance spectroscopy, photoluminescence, radioluminescence, thermoluminescence, and optically stimulated luminescence. Light yield from the nanophosphor oxyorthosilicates is of the same magnitude as the bulk counterparts; probably this yield is due at least partially to reduced self-absorption as a result of structural changes, reduced quenching effects due to particle size and increased disorder, and reduced electron-trapping defects. Al₂O₃ storage nanophosphors, which have numerous applications in personal and environmental dosimetry, can yield structural and luminescence properties similar to commercially available products, but the light yield is currently reduced as compared to the commercial samples. Future research will focus on more sophisticated nanophosphor structures and advanced analytical techniques. The DOE Office of Science, Basic Energy Science program funded the research.

X-band EPR spectrometer with the Oxford cryostat used in the nanophosphor study.

July 14, 2008

LANL Scientists Co-Organize Nile River Basin Workshop

Giday WoldeGabriel (EES-9), Gary Geernaert (INST-IGPP), and James Doyle (D-4) co-organized an international scientific workshop, "Hydrology and Ecology of the Nile River Basin under Extreme Climatic Conditions" at the Faculty of Science conference center of Addis Ababa University, Ethiopia. The National Science Foundation and the Nile Basin Initiative Secretariat in Uganda were the primary financial sponsors for the workshop.

The goal of the workshop was to assess the impact of short- and long-term climatic perturbations and other factors on the Nile River basin water resources and to initiate scientific dialog and collaborations among scientists from the ten Nile Basin countries. Chronic water resources issues caused by persistent severe droughts and environmental stresses coupled with political and economic instabilities, primitive land-use practices, overpopulation, and desertification have greatly impacted the Nile River basin.

WoldeGabriel presented "Significance of Past Climatic Records in Terrestrial Sediments for Assessing Current and Future Conditions" and "Scientific and Technological Interventions to Alleviate Transboundary Water Concerns in the Nile River Basin". Geernaert presented "Water Resources of the Nile Basin - Extreme Events, Climate Change, and Regional Security" and "Climate Change Predictions for East Africa - Certainty, Uncertainty, and Recommendations". Doyle's talk was "Energy Resources and Infrastructure Interdependence".

The four-day workshop included participants from the Nile basin countries of Burundi, D.R. Congo, Egypt, Ethiopia, Rwanda, Sudan, Tanzania, and Uganda; the Nile Basin Initiative Secretariat in Uganda; the International Water Management Institute; the International Livestock Resources Institute for Africa; and the U.S. (LANL, NM State University, University of Arizona, U.C. Santa Barbara, USGS/EROS, South Dakota State University, Missouri Science and Technology University at Rolla, Florida International University, and the South Florida Water Management District). Topics on climate change, land-use dynamics, hydrology of the Nile River Basin, hydrological modeling and simulations of the basin, hydrometrological analysis, river basin management and water-use research results were presented. The workshop concluded with the selection of a task force to assess project development and proposal preparation opportunities on major topics related to climate change and variability, capacity building, and knowledge management and sharing. WoldeGabriel (EES-9) and Canisius Kanangire (Head of the Applied Technical Training of the Nile Basin Initiative Secretariat) lead the task force.

Click to view larger image.

Other Archived Highlights