The Structural Determinants Accounting for the Broad Substrate Specificity of the Quorum Quenching Lactonase GcL
Abstract not provided
Bergonzi, Celine↗
SEARCH · Search NASA
Results for “Accountability”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Enhanced prediction of Cs removal by CST from Hanford tank waste with K accountability
Abstract The treatment of Hanford tank waste is one of the most challenging environmental cleanup activities to date. To expedite the processing of liquid waste stored in underground tanks in Washington State it is necessary to remove the significant dose contributor, 137 Cs. Crystalline silicotitanate ion exchanger is currently used to remove 137 Cs from the aqueous phase of Hanford tank wastes in preparation for vitrification at the Waste Treatment and Immobilization Plant (WTP). Improving the understanding of potassium impacts on ion exchange behavior of Cs will help in the operation of a critical component of one of the most complex treatment processes in the world today. Optimization of this process can result in significant cost savings and less waste production. Toward this effort, a series of batch contact tests varied in potassium concentration were conducted to look at the impact of potassium concentration on Cs distribution. Experimental distribution ratios ( K d ) were compared to the distribution ratios predicted using the ZAM model. A significant underprediction of Cs capacity in the presence of potassium was seen with the existing model. A revision of the equilibrium constants was determined and provided a statistically better fit for determining the Cs K d values in tank waste matrices.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Chromosome aberrations among atomic-bomb survivors exposed in utero: updated analysis accounting for revised radiation doses and smoking
A previous study of peripheral blood lymphocyte translocations around age 40 among atomic-bomb survivors exposed in utero revealed no overall association with radiation dose—despite a clear association between translocations and dose among their mothers—but the data suggested an increase at doses below 100 mGy with a definite peak. That analysis of the in utero-exposed survivors did not adjust for their subsequent smoking behavior, an established cause of chromosomal aberrations, or their subsequent exposures to medical irradiation, a potential mediator. In addition, atomic-bomb survivor radiation dose estimates have subsequently been updated and refined. We therefore re-estimated the dose response using the latest DS02R1 dose estimates and adjusting for smoking as well as for city and proximal–distal location at the time of exposure to the atomic bomb. Sex of the survivor, mother’s age around the time of conception, and approximate trimester of gestation at the time of exposure were also considered as explanatory variables and modifiers. Precision of the estimated dose response was slightly lower due to greater variability near zero in the updated dose estimates, but there was little change in evidence of a low-dose increase and still no suggestion of an overall increase across the entire dose range. Adjustment for smoking behavior led to a decline in background number of translocations (the dose–response intercept), but smoking did not interact with dose overall (across the entire dose range). Adjustment for medical irradiation did not alter the association between dose and translocation frequency. Sex, mother’s age, and trimester were not associated with number of translocations, nor did they interact with dose overall. Interactions with dose in the low-dose range could not be evaluated because of numerical instability.
59 BASIC BIOLOGICAL SCIENCES↗
Concepts of association between cancer and ionising radiation: accounting for specific biological mechanisms
The probability that an observed cancer was caused by radiation exposure is usually estimated using cancer rates and risk models from radioepidemiological cohorts and is called assigned share (AS). This definition implicitly assumes that an ongoing carcinogenic process is unaffected by the studied radiation exposure. However, there is strong evidence that radiation can also accelerate an existing clonal development towards cancer. In this work, we define different association measures that an observed cancer was newly induced, accelerated, or retarded. The measures were quantified exemplarily by Monte Carlo simulations that track the development of individual cells. Three biologically based two-stage clonal expansion (TSCE) models were applied. In the first model, radiation initiates cancer development, while in the other two, radiation has a promoting effect, i.e. radiation accelerates the clonal expansion of pre-cancerous cells. The parameters of the TSCE models were derived from breast cancer data from the atomic bomb survivors of Hiroshima and Nagasaki. For exposure at age 30, all three models resulted in similar estimates of AS at age 60. For the initiation model, estimates of association were nearly identical to AS. However, for the promotion models, the cancerous clonal development was frequently accelerated towards younger ages, resulting in associations substantially higher than AS. This work shows that the association between a given cancer and exposure in an affected person depends on the underlying biological mechanism and can be substantially larger than the AS derived from classic radioepidemiology.
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
A Brief Account of Steven Weinberg’s Legacy in ab initio Many-Body Theory
In this contribution to the special issue “Celebrating 30 years of Steven Weinberg’s papers on Nuclear Forces from Chiral Lagrangians,” we emphasize the important role chiral effective field theory has played in leading nuclear physics into a precision era. To this end, we share our perspective on a few of the recent advances made in ab initio calculations of nuclear structure and nuclear matter observables, as well as Bayesian uncertainty quantification of effective field theory truncation errors.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Accounting for Environmental Aspects in Water-Chemistry Optimization of the Second Loop of NPP with VVER
A problem in operating NPP with VVER is that waste solutions containing ethanolamine and ammonia from regeneration of ion-exchange filters from the second loop must be processed. The amount of ammonia in the regeneration solutions is equal to 85% of the total amount of the contaminating substances. The water chemistry regime of the second loop without ammonia or with ammonia replaced by dimethylamine is examined. It is shown that the use of dimethylamine makes it possible to increase the duration of the filtration cycle for ion-exchange filters of the purification systems, decrease the concentration of products of corrosion, reduce the environmental impact, and simplify the waste water purification technology.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Distance Determination by Gated Viewing Systems Taking into Account the Illuminating Pulse Shape
For gated viewing systems with triangular and trapezoidal illuminating pulses, we have obtained the range-intensity profiles (RIPs) of the signal as the time delay was varied between the leading edges of the gate pulse and the illuminating pulse. We have established that if the duration of the illuminating pulse Δt{sub las} is less than or equal to the duration of the gate pulse Δt{sub IC}, then the expressions for the characteristic distances are the same as for rectangular pulses and they can be used to determine the distance to objects. When Δt{sub las} > Δt{sub IC}, in the case of triangular illuminating pulses the RIP is bell-shaped. For trapezoidal pulses, the RIP is bell-shaped with or without a plateau section. We propose an empirical method for determining the characteristic distances to the RIP maximum and the boundary points for the plateau section, which we then use to calculate the distance to the object. Using calibration constants, we propose a method for determining the distance to an object and we have experimentally confirmed the feasibility of this method.
42 ENGINEERING↗
Accounting for the Complex Surface Structure in Ellipsometric Studies of the Effects of Magnetron Sputtering Modes on the Growth and Optical Properties of In{sub 2}O{sub 3} Films
The efficiency of invoking additional information on optical transmission in solving the inverse problem of ellipsometry by a minimization method is demonstrated in practice for In{sub 2}O{sub 3} fi doped and nondoped with Sn on Al{sub 2}O{sub 3} (012) substrates. This approach allows the thickness and refractive index of thin films with rough surfaces to be uniquely determined. Solutions of the inverse problem in the framework of one-, two-, and multilayer models are compared. The last provides the best description of the experimental data and the correct parameters of the samples. The dependences of the investigated properties of films produced with different magnetron sputtering modes are found using the above methods and models and do not contradict general concepts about the film formation by this material.
36 MATERIALS SCIENCE↗
Mathematical Simulation of the Migration of Radionuclides in a Soil Medium Under Nonisothermal Conditions with Account for Catalytic Microparticles and Nonlinear Processes
The problem of mathematical simulation of the vertical migration of radionuclides in a catalytic porous medium under nonisothermal conditions is considered. A numerical solution of the corresponding one-dimensional nonlinear boundary-value problem is obtained by the finite difference method. Numerical experiments are carried out and their analysis is made.
54 ENVIRONMENTAL SCIENCES↗
Nonparametric Method of Least Squares: Accounting for Seasonality
We consider the problem of restoring a nonparametric dependence described by the sum of linear trend and seasonal component, i.e., a periodic function with the known period. We obtain the asymptotic distribution of the parameter estimates and the trend component. We find the mathematical expectation of the residual sum of squares. We also develop the methods of estimation of the seasonal component and construction of the interval forecast.
97 MATHEMATICS AND COMPUTING↗
Accounting for Melt Flow Pattern and Solid Fraction Evolution in DC Casting of Al-Cu Alloy Using v{sup 2}−f Turbulence Model
Experimental techniques remain reliable approaches for investigating the effects of parameters of the direct chill (DC) casting process on macrosegregation, grain structure formation, and surface quality. However, experimental analysis methods of these effects are expensive and can often prove difficult to implement. Understanding of the complex physics of the solidification process remains limited, and this makes it indispensable to use accurate numerical modeling tools as a complement to experiments. Numerical modeling without consideration of turbulent flow is unsuitable for application to solidification occurring during DC casting, since significant turbulent flow exists in the upper section of the cast, where the liquid pool exists. The present work employed a low-Re v{sup 2}−f turbulence model and a dual-zone solidification flow model to predict the melt flow pattern, turbulence level, sump depth, transition zone thickness, and mushy zone thickness in the DC casting of Al-Cu alloy. The obtained results provided evidence of significant damping of the flow in the slurry zone. Furthermore, results of different simulation cases revealed a narrower transition zone and shallower sump.
36 MATERIALS SCIENCE↗
Approximate methodology to account for effects of coherent structures on sediment entrainment in RANS simulations with a movable bed and applications to pier scour
Not Available
Cheng, Zhengyang (ORCID:0000000216060767)↗
Nuclear material input accountancy with a representative sampling method
Not Available
Yoo, Tae-Sic (ORCID:0000000222445700)↗
Modeling and experimental validation of rotary riffling method for nuclear material input accountancy
Not Available
Yoo, Tae-Sic (ORCID:0000000222445700)↗
Intrinsic DNA Shape Accounts for Affinity Differences between Hox-Cofactor Binding Sites
Abstract not provided
Zeiske, Tim↗
Investigation of the changes in microstructure and transport properties of leached cement pastes accounting for mix composition
Ca-leaching of cement-based materials induces detrimental effects on properties related to long-term durability. A better understanding of leaching degradation in terms of alterations in mineralogy, microstructure, and transport properties is important for long-term assessments of concrete and reinforced concrete structures used in nuclear waste disposal systems or in hydro structures. However, the decalcification process is not easy to study because it is extremely slow. In this study, an ammonium nitrate (NH{sub 4}NO{sub 3}) solution of 6 mol/l was used to accelerate the leaching kinetics. The experiments were performed on cement paste samples with different water/powder (w/p) and limestone filler (LS) replacement ratios. Both the change of sample mass over time and the amount of calcium ion leached out were monitored during the test. Different post-analysis techniques including SEM/SEM-EDX, XRD/QXRD, MIP, ion chromatography, and N{sub 2}-adsorption were used to characterize the microstructural and mineralogical changes. The effect of accelerated leaching on transport properties was studied by measuring the changes in water permeability and diffusivity of dissolved gases. Results showed that the square-root-time law of degradation was applicable under accelerated conditions. Both higher w/p ratios and LS replacements increased the rate of leaching propagation; the former had a more significant effect. The accelerated leaching significantly altered the microstructure of the cement paste to a material with a higher specific surface area, increased total porosity and a shift to larger pore sizes. Those changes led to a significant increase in water permeability (one to two orders of magnitude) and diffusivity (less than one order) depending on degradation state.
36 MATERIALS SCIENCE↗
A new phase field fracture model for brittle materials that accounts for elastic anisotropy
Not Available
Zhang, Shuaifang↗