Innovative characterization, monitoring and sensor technologies for environmental radioactivity at USDOE sites

The mission of the U. S. Department of Energy Office of EnvironmentalManagement (EM) is to clean up its contaminated sites from the past productionof nuclear weapons. Within EM, the Office of Science and Technology (OST)is responsible for providing a full range of science and technology resourcesneeded to support resolution of EM cleanup and long-term environmental stewardshipproblems. This responsibility includes implementation of a technology developmentpathway from basic research to development, demonstration, and deploymentof scientific and technological solutions needed by DOE sites. One OST Programis the Characterization, Monitoring, and Sensor Technology Crosscutting Program(CMST-CP), which aims to provide innovative technologies (i.e., faster, better,cheaper, and/or safer) for environmental characterization and monitoring.This paper describes several technologies that CMST-CP has supported for developmentwith significant benefits realized or projected over the baseline characterizationand monitoring practices. Examples of these technologies include mapping ofsubsurface radioactivity using Cone Penetrometer and drilling techniques;a Rapid Liquid Sampler for Sr, Ra, Tc, and Cs using 3M Empore Rad Disks;Long-Range Alpha Detectors; a Compact High Resolution Spectrometer; BetaScintfor determination of Sr in soil; Laser-Induced Fluorescence Imaging techniquesfor mapping U on surfaces; the Environmental Measurements While Drilling System;and the Expedited Site Characterization methodology.     

New evidence for multiple binding sites for sulfur at the Ni(100)-vacuum interface

Measurements of adsorbate-derived peaks in angle-resolved photoemission energy distribution may provide a useful method for the study of bulk/surface diffusion of contaminants in metals. Energy distributions for c(2 × 2) sulfur on Ni(100) at 50° (±4°) collection angle along (001) for nω = 21.2 eV (HeI) are characterized by a single sulfur-derived peak at 4.5 eV binding energy, believed to be due to sulfur in the four-fold hollow surface site determined by LEED. Further sulfur dosage or excessive heating results in the appearance of a second peak in the spectrum, at 1.25 eV higher binding energy, while maintaining a sharp c(2 × 2) LEED structure. The new binding configuration indicated by the second sulfur peak is interpreted as the penetration of sulfur into the substrate. This interpretation is supported by further studies of the dependence of the higher binding energy peak on temperature and dosage. This method of observing bulk-surface diffusion should be applicable to many other adsorbate/substrate systems, as long as the adsorbate-derived peak can be observed and identified.     

Three-dimensional imaging of colloidal glasses under steady shear

Using fast confocal microscopy we image the three-dimensional dynamics of particles in a yielded hard-sphere colloidal glass under steady shear. The structural relaxation, observed in regions with uniform shear, is nearly isotropic but is distinctly different from that of quiescent metastable colloidal fluids. The inverse relaxation time tau(alpha)(-1) and diffusion constant D, as functions of the local shear rate gamma*, show marked shear thinning with tau(alpha)(-1) proportional to D proportional to gamma*(0.8) over more than two decades in gamma*. In contrast, the global rheology of the system displays Herschel-Bulkley behavior. We discuss the possible role of large scale shear localization and other mechanisms in generating this difference.     

Strong correlation between SHAPE chemistry and the generalized NMR order parameter (S2) in RNA

The functions of most RNA molecules are critically dependent on the distinct local dynamics that characterize secondary structure and tertiary interactions and on structural changes that occur upon binding by proteins and small molecule ligands. Measurements of RNA dynamics at nucleotide resolution set the foundation for understanding the roles of individual residues in folding, catalysis, and ligand recognition. In favorable cases, local order in small RNAs can be quantitatively analyzed by NMR in terms of a generalized order parameter, S2. Alternatively, SHAPE (selective 2'-hydroxyl acylation analyzed by primer extension) chemistry measures local nucleotide flexibility in RNAs of any size using structure-sensitive reagents that acylate the 2'-hydroxyl position. In this work, we compare per-residue RNA dynamics, analyzed by both S2 and SHAPE, for three RNAs: the HIV-1 TAR element, the U1A protein binding site, and the Tetrahymena telomerase stem loop 4. We find a very strong correlation between the two measurements: nucleotides with high SHAPE reactivities consistently have low S2 values. We conclude that SHAPE chemistry quantitatively reports local nucleotide dynamics and can be used with confidence to analyze dynamics in large RNAs, RNA-protein complexes, and RNAs in vivo.     

Surface morphology of organic thin films at various vapor flux

The surface morphology of the organic energetic material pentaerythritol tetranitrate (PETN) grown on silicon substrates has been investigated. The surface structure of the films reveal clearly differentiated morphologies which is dependent on the vapor flux. Dendrite crystals are formed with flux of 0.03 nm/s while the morphology shows a transition from dendrite branches to grain growth as the flux is increased to 0.3 nm/s. The deposition thickness did not show an obvious influence on the surface microstructure. Therefore, the deposition flux allows the production of PETN films with desired surface morphology in a controllable and reproducible way.     

高分离度快速液相色谱法测定牛黄解毒片中黄芩苷的含量

采用高分离度快速液相色谱(RRLC)测定牛黄解毒片中黄芩苷的含量。色谱柱为Zorbax XDB-C18(4.6×50mm,1.8μm),流动相为甲醇-水-磷酸(45∶55∶0.2),检测波长315nm,流速0.5mL.min-1,柱温为30℃。黄芩苷在0.15—1.35μg(r=0.9999)范围内峰面积与浓度呈良好的线性关系,加样回收率为100.41%,RSD=1.42%。采用高分离度快速液相色谱(RRLC)测定复方牛黄解毒片中黄芩苷的含量,缩短了保留时间,提高了效率,降低了成本。本方法简便、准确,结果稳定。