Pretreatment of Hanford medium-curie wastes by fractional crystallization

Acceleration of the schedule for decontamination of the Hanford site using bulk vitrification requires implementation of a pretreatment operation. Medium-curie waste must be separated into two fractions: one is to go to a waste treatment and immobilization plant and a second, which is low-activity waste, is to be processed by bulk vitrification. The work described here reports research on using fractional crystallization for that pretreatment. Sodium salts are crystallized by evaporation of water from solutions simulating those removed from single-shell tanks, while leaving cesium in solution. The crystalline products are then recovered and qualified as low-activity waste, which is suitable upon redissolution for processing by bulk vitrification. The experimental program used semibatch operation in which a feed solution was continuously added to maintain a constant level in the crystallizer while evaporating water. The slurry recovered at the end of a run was filtered to recover product crystals, which were then analyzed to determine their composition. The results demonstrated that targets on cesium separation from the solids, fractional recovery of sodium salts, and sulfate content of the recovered salts can be achieved by the process tested.     

Identification of the Zirconia Phases by Means of Raman Spectroscopy for Specimens Prepared by FIB Lift-Out Technique

Oxidation of Metals - The zirconium–zirconia interface that developed during high-temperature corrosion of pure zirconium was investigated. Samples were oxidized at...     

Sizing nanomatter in biological fluids by fluorescence single particle tracking

Accurate sizing of nanoparticles in biological media is important for drug delivery and biomedical imaging applications since size directly influences the nanoparticle processing and nanotoxicity in vivo. Using fluorescence single particle tracking we have succeeded for the first time in following the aggregation of drug delivery nanoparticles in real time in undiluted whole blood. We demonstrate that, by using a suitable surface functionalization, nanoparticle aggregation in the blood circulation is prevented to a large extent.     

Parametric imaging for characterizing focal liver lesions in contrast-enhanced ultrasound

The differentiation between benign and malignant focal liver lesions plays an important role in diagnosis of liver disease and therapeutic planning of local or general disease. This differentiation, based on characterization, relies on the observation of the dynamic vascular patterns (DVP) of lesions with respect to adjacent parenchyma, and may be assessed during contrast-enhanced ultrasound imaging after a bolus injection. For instance, hemangiomas (i.e., benign lesions) exhibit hyper-enhanced signatures over time, whereas metastases (i.e., malignant lesions) frequently present hyperenhanced foci during the arterial phase and always become hypo-enhanced afterwards. The objective of this work was to develop a new parametric imaging technique, aimed at mapping the DVP signatures into a single image called a DVP parametric image, conceived as a diagnostic aid tool for characterizing lesion types. The methodology consisted in processing a time sequence of images (DICOM video data) using four consecutive steps: (1) pre-processing combining image motion correction and linearization to derive an echo-power signal, in each pixel, proportional to local contrast agent concentration over time; (2) signal modeling, by means of a curve-fitting optimization, to compute a difference signal in each pixel, as the subtraction of adjacent parenchyma kinetic from the echopower signal; (3) classification of difference signals; and (4) parametric image rendering to represent classified pixels as a support for diagnosis. DVP parametric imaging was the object of a clinical assessment on a total of 146 lesions, imaged using different medical ultrasound systems. The resulting sensitivity and specificity were 97% and 91%, respectively, which compare favorably with scores of 81 to 95% and 80 to 95% reported in medical literature for sensitivity and specificity, respectively.     

Numerical design of experiment for sensitivity analysis--application to skin burn injury prediction.

Temperature evolution and skin burn process resulting from a laser radiation exposure are investigated in this paper. Transient temperature in skin is numerically estimated using a 1-D multilayered model based on Penne's equation. The degree of burn injury is numerically evaluated by using an Arrhenius-type function. Unfortunately, most of the mathematical model parameters are not well defined in literature. Thus, a sensitivity analysis has been performed in order to evaluate the effect of each parameters inaccuracy on temperature estimation and on burn injuries prediction (according to several authors' characterization). Investigated parameters uncertainties that crucially invalidate the thermal model are as follows: epidermis and dermis volumetric heat, extinction coefficient, and skin thickness of the affected area. Considering the damage prediction, the activation energy is a key parameter for the validation of an efficient predictive tool.     

Thermochemistry of Species Potentially Formed During NTO/MMH Hypergolic Ignition

This paper deals with the gas‐phase thermodynamic properties of endothermic compounds potentially formed during monomethylhydrazine (MMH)/nitrogen tetroxide (NTO) hypergolic reactivity. The standard enthalpies of formation at 298.15 K are determined by means of quantum chemistry calculations along with protocols developed for these compounds. The resultant data, currently previously unavailable for almost all of these compounds, are potentially critical to the modeling of combustion chemistry of this bipropellant combination.     

Synthesis of titanium dioxide nanoparticles by reactive DC magnetron sputtering

Nanometer-sized titanium dioxide (TiO₂) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes, the mean nanoparticle diameter and the coverage fraction of the substrate by the nanoparticles (NPs) were measured at 19 nm and 30%, respectively. Moreover, electron diffraction analysis showed that the TiO₂ NPs' crystalline structure on the carbon substrate was a mixture of anatase and rutile. Finally, we provided information on the TiO₂ initial growth stage: crystalline NPs were formed after deposition of amorphous nanoparticles on the substrate and heating.     

Time-scale joint representation of DNS and LES numerical data

A spectral analysis and a multiscale study are performed on the numerical data obtained from direct numerical simulation and large-eddy simulation of the turbulent flow in a cubical lid-driven cavity. The analyzed data or signals are picked at three specific points inside the cavity allowing to investigate three drastically different flow regimes over time: laminar, transitional and turbulent. In comparison with direct numerical simulation, large-eddy simulation not only have a reduced resolution in space but also in time. In this context a wavelet analysis is chosen to study signals from large-eddy simulation, to provide a ‘local’ analysis of transient turbulent events. A time-scale joint representation is generated by continuous wavelet transform and compared with the time-scale joint representation of the direct numerical simulation. In this framework, the main objective of this study is to confirm the correlation between the computed physical quantities and those expected theoretically.