The Lawrence Livermore National Laboratory (LLNL) Chemical & Biological National Security Program (CBNP) provides science, technology, and integrated systems for chemical and biological security. Our approach is to develop and field systems that dramatically improve the nation's capabilities to prevent, prepare for, detect, and respond to terrorist use of chemical or biological weapons.

We observed Titan in 1996-2004 with high-resolution 2 {micro}m speckle and adaptive optics imaging at the W.M. Keck Observatory. By observing in a 2 {micro}m broadband filter we obtain images that have contributions from both Titan's surface and atmosphere. We have modeled Titan's atmosphere using a plane-parallel radiative transfer code that has been corrected to agree with 3-D Monte Carlo predictions. We find that Titan's surface albedo ranges from {le} 0:02 in the darkest equatorial region of the trailing hemisphere to {approx_equal} 0:1 in the brightest areas of the leading hemisphere. Over the past quarter of a Saturnian year haze optical depth in Titan's Southern hemisphere has decreased substantially from a value of 0.48 in 1996 down to 0.18 in 2004, while the northern haze has been increasing over the past few years. As a result of these changes, in 2004 the North/South haze asymmetry at K' band has disappeared.

On the basis of the observation that conserved positions in transcription factor binding sites are often clustered together, we propose a simple extension to the model-based motif discovery methods. We assign position-specific prior distributions to the frequency parameters of the model, penalizing deviations from a specified conservation profile. Examples with both simulated and real data show that this extension helps discover motifs as the data become noisier or when there is a competing false motif.

This study assessed chemical treatment options for decomposing the tetraphenylborate in High Level Waste (HLW) Tank 48H. Tank 48H, located at the Savannah River Site in Aiken, SC, contains approximately one million liters of HLW. The tetraphenylborate slurry represents legacy material from commissioning of an In Tank Precipitation process to separate radioactive cesium and actinides from the non radioactive chemicals. During early operations, the process encountered an unplanned chemical reaction that catalytically decomposed the excess tetraphenylborate producing benzene. Subsequent research indicated that personnel could not control the operations within the existing equipment to both meet the desired treatment rate for the waste and maintain the benzene concentration within allowable concentrations. Since then, the Department of Energy selected an alternate treatment process for handling high-level waste at the site. However, the site must destroy the tetraphenylborate before returning the tank to HLW service. The research focuses on identifying treatments to decompose tetraphenylborate to the maximum extent feasible, with a preference for decomposition methods that produce carbon dioxide rather than benzene. A number of experiments examined whether the use of oxidants, catalysts or acids proved effective in decomposing the tetraphenylborate. Additional experiments developed an understanding of the solid, liquid and gas decomposition …

Management of surface water quality is often complicated by interactions between surface water and groundwater. Traditional Land-Surface Models (LSM) used for numerical weather prediction, climate projection, and as inputs to water management decision support systems, do not treat the LSM lower boundary in a fully process-based fashion. LSMs have evolved from a leaky bucket to more sophisticated land surface water and energy budget models that typically have a so-called basement term to depict the bottom model layer exchange with deeper aquifers. Nevertheless, the LSM lower boundary is often assumed zero flux or the soil moisture content is set to a constant value; an approach that while mass conservative, ignores processes that can alter surface fluxes, runoff, and water quantity and quality. Conversely, groundwater models (GWM) for saturated and unsaturated water flow, while addressing important features such as subsurface heterogeneity and three-dimensional flow, often have overly simplified upper boundary conditions that ignore soil heating, runoff, snow and root-zone uptake. In the present study, a state-of-the-art LSM (CLM) and a variably-saturated GWM (ParFlow) have been coupled as a single column model. A set of simulations based on synthetic data and data from the Project for Intercomparison of Landsurface Parameterization Schemes (PILPS), version …

This paper presents a method for solving Poisson's equation with Dirichlet boundary conditions on an irregular bounded three-dimensional region. The method uses a nodal-point discretization and adaptive mesh refinement (AMR) on Cartesian grids, and the AMR multigrid solver of Almgren. The discrete Laplacian operator at internal boundaries comes from either linear or quadratic (Shortley-Weller) extrapolation, and the two methods are compared. It is shown that either way, solution error is second order in the mesh spacing. Error in the gradient of the solution is first order with linear extrapolation, but second order with Shortley-Weller. Examples are given with comparison with the exact solution. The method is also applied to a heavy-ion fusion accelerator problem, showing the advantage of adaptivity.

Modern force microscopy techniques allow researchers to use mechanical forces to probe interactions between biomolecules. However, such measurements often happen in non-equilibrium regime, which precludes straightforward extraction of the equilibrium energy information. Here we use the work averaging method based on Jarzynski equality to reconstruct the equilibrium interaction potential from the unbinding of a complementary 14-mer DNA duplex from the results of non-equilibrium single-molecule measurements. The reconstructed potential reproduces most of the features of the DNA stretching transition, previously observed only in equilibrium stretching of long DNA sequences. We also compare the reconstructed potential with the thermodynamic parameters of DNA duplex unbinding and show that the reconstruction accurately predicts duplex melting enthalpy.

We have used photo-modulated transmission and optical absorption spectroscopies to measure the composition dependence of interband optical transitions in N-rich GaN{sub 1-x}As{sub x} alloys with x up to 0.06. The direct bandgap gradually decreases as x increases. In the dilute x limit, the observed band gap approaches 2.8 eV; this limiting value is attributed to a transition between the As localized level, which has been previously observed in As-doped GaN at 0.6 eV above the valence band maximum in As-doped GaN, and the conduction band minimum. The structure of the valence band of GaN{sub 1-x}As{sub x} is explained by the hybridization of the localized As states with the extended valence band states of GaN matrix. The hybridization is directly confirmed by soft x-ray emission experiments. To describe the electronic structure of the GaN{sub 1-x}As{sub x} alloys in the entire composition range a linear interpolation is used to combine the effects of valence band hybridization in N-rich alloys with conduction band anticrossing in As-rich alloys.

Modeling fracture-matrix interaction within a multiple-phase flow system is a key issue for fractured reservoir simulation. Commonly used mathematical models for dealing with such interactions employ dual- or multiple-continuum concepts, in which fractures and matrix are represented as overlapping, different, but interconnected continua, described by parallel sets of conservation equations. The conventional single-point upstream weighting scheme is most commonly used to estimate flow mobility for fracture-matrix flow. However, such a scheme may have serious limitations or flaws, which lead to unphysical solutions or significant numerical errors. To overcome the limitations of the conventional upstream weighting scheme, this paper presents a physically based modeling approach for estimating physically correct relative permeability in calculating multiphase flow between fractures and the matrix, using continuity of capillary pressure at the fracture-matrix interface. The proposed approach has been implemented into two multiphase reservoir simulators and verified using analytical solutions and laboratory experimental data. The new method is demonstrated to be accurate, numerically efficient, and easy to implement in dual- or multiple-continuum reservoir simulators.

The current conceptual design of proposed Large EMCal of ALICE at LHC is based largely on the scintillating mega-tile/fiber technology implemented in CDF Endplug upgrade project and in both barrel and endcap electromagnetic calorimeters of the STAR. The cost of scintillating material leads us to the choice of extruded polystyrene based scintillator, which is available in new FNAL-NICADD facility. Result of optical measurements, such as light yield and light yield variation, show that it is possible to use this material as active media of Large EMCal of ALICE at LHC.