Development of predictive simulation capability for reactive multiphase flow

This is the final report of a Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to develop a self-sustained research program for advanced computer simulation of industrial reactive multiphase flows. The prototype research problem was a three-phase alumina precipitator used in the Bayer process, a key step in aluminum refining. Accomplishments included the development of an improved reaction mechanism of the alumina precipitation growth process, the development of an efficient methods for handling particle size distribution in multiphase flow simulation codes, the incorporation of precipitation growth and agglomeration kinetics in LANL's CFDLIB multiphase flow code library and the evaluation of multiphase turbulence closure models for bubbly flow simulations

Electrical Measurements on the Greenland Ice Sheet Project 2 Core

The Greenland Ice Sheet Project 2 (GISP2) electrical conductivity measurement (ECM) record is an indication of the concentration of H+ in the core. The ECM detected seasonal variations in the nitrate concentration of the core which were used to assist in dating the core by annual layer counting. Volcanic eruptions that produce acidic aerosols are recorded in the ECM record. Evidence of biomass burning is detected by the ECM because fire-related ammonium emissions neutralize the acids in the core. Rapid climate transitions associated with the Younger Dryas and Dansgaard/Oeschger interstadial events alter the concentration of alkaline dust and are detected by the ECM. The ECM has been used to develop stratigraphic ties between the GISP2 and the Greenland Ice Core Project cores. Users of the data should be aware of some instrument-related artifacts in the ECM record

Measurements of the magnetic field induced by a turbulent flow of liquid metal

Initial results from the Madison Dynamo Experiment provide details of the inductive response of a turbulent flow of liquid sodium to an applied magnetic field. The magnetic field structure is reconstructed from both internal and external measurements. A mean toroidal magnetic field is induced by the flow when an axial field is applied, thereby demonstrating the omega effect. Poloidal magnetic flux is expelled from the fluid by the poloidal flow. Small-scale magnetic field structures are generated by turbulence in the flow. The resulting magnetic power spectrum exhibits a power-law scaling consistent with the equipartition of the magnetic field with a turbulent velocity field. The magnetic power spectrum has an apparent knee at the resistive dissipation scale. Large-scale eddies in the flow cause significant changes to the instantaneous flow profile resulting in intermittent bursts of non-axisymmetric magnetic fields, demonstrating that the transition to a dynamo is not smooth for a turbulent flow.Comment: 9 pages, 11 figures, invited talk by C. B. Forest at 2005 APS DPP meeting, resubmitted to Physics of Plasma

A semi-automated measurement technique for the assessment of radiolucency

The assessment of radiolucency around an implant is qualitative, poorly defined and has low agreement between clinicians. Accurate and repeatable assessment of radiolucency is essential to prevent misdiagnosis, minimize cases of unnecessary revision, and to correctly monitor and treat patients at risk of loosening and implant failure. The purpose of this study was to examine whether a semi-automated imaging algorithm could improve repeatability and enable quantitative assessment of radiolucency. Six surgeons assessed 38 radiographs of knees after unicompartmental knee arthroplasty for radiolucency, and results were compared with assessments made by the semi-automated program. Large variation was found between the surgeon results, with total agreement in only 9.4% of zones and a kappa value of 0.602; whereas the automated program had total agreement in 81.6% of zones and a kappa value of 0.802. The software had a ‘fair to excellent’ prediction of the presence or the absence of radiolucency, where the area under the curve of the receiver operating characteristic curves was 0.82 on average. The software predicted radiolucency equally well for cemented and cementless implants (p = 0.996). The identification of radiolucency using an automated method is feasible and these results indicate that it could aid the definition and quantification of radiolucency

Problems and Paradoxes in Economic and Social Policies of Modern Welfare States

Relationships between economic growth rates and the expansion of welfare expenditures in Western nations are examined. The point is made that real gross national product grew rapidly from about 1959 until about 1973, but that since 1973 it has either grown slowly or not at all, while welfare expenditures and entitlements have continued to escalate. Forecasts of a variety of important economic variables in these countries for the near term are presented and discussed, and it is concluded that despite the current modest economic improvement, difficulties in funding welfare states will continue throughout the remainder of the 1980s. Some consideration is given to problems in welfare states to the end of the century, and further difficulties in funding and managing these states are forecast for this period as well. Problems of welfare states are not regarded as short-term by-products of maladjustments experienced in the Western world in the last 10 years but rather as long-term characteristics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67103/2/10.1177_000271628547900102.pd

Surface Meltwater Impounded by Seasonal Englacial Storage in West Greenland

The delivery of surface meltwater through englacial drainage systems to the bed of the Greenland Ice Sheet modulates ice flow through basal lubrication. Recent studies in Southeast Greenland have identified a perennial firn aquifer; however, there are few observations quantifying the input or residence time of water within the englacial system and it remains unknown whether water can be stored within solid ice. Using hourly stationary radar measurements, we present observations of englacial and episodic subglacial water in the ablation zone of Store Glacier in West Greenland. We find significant storage of meltwater in solid ice damaged by crevasses extending down to 48 m below the ice surface during the summer which is released or refrozen during winter. This is a significant hydrological component newly observed in the ablation zone of Greenland that could delay the delivery of meltwater to the bed, changing the ice dynamic response to surface meltwater.Publisher PDFPeer reviewe

Exposing the Interplay Between Enzyme Turnover, Protein Dynamics and the Membrane Environment in Monoamine Oxidase B

There is an increasing realization that structure-based drug design may show improved success rates by understanding the ensemble of conformations and sub-states accessible to an enzyme and how the environment affects this ensemble. Human monoamine oxidase B (MAO-B) catalyzes the oxidation of amines and is inhibited for the treatment of both Parkinson’s disease and depression. Despite its clinical importance, its catalytic mechanism remains unclear and routes to drugging this target would be valuable and relevant. Evidence of a radical in either the transition state or resting state of MAO-B is present throughout the literature, and is suggested to be a flavin semiquinone, a tyrosyl radical or both. Here we see evidence of a resting state flavin semiquinone, via absorption redox studies and electron paramagnetic resonance, suggesting that the anionic semiquinone is biologically relevant. Based on enzyme kinetic studies, enzyme variants and molecular dynamics simulations we find evidence for the crucial importance of the membrane environment in mediating the activity of MAO-B and that this mediation is related to effects on the protein dynamics of MAO-B. Further, our MD simulations identify a hitherto undescribed entrance for substrate binding, membrane modulated substrate access, and indications for half-site reactivity: only one active site is accessible to binding at a time. Our study combines both experimental and computational evidence to illustrate the subtle interplay between enzyme activity, protein dynamics and the immediate membrane environment. Understanding key biomedical enzymes to this level of detail will be crucial to inform strategies (and binding sites) for rational drug design for these drug targets