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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.

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At least 1,729 records · Page 96
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Investigation of aluminum nitrate as a set retarder of magnesium potassium phosphate cement: Mechanisms involved in diluted suspension

In this study, the influence of aluminum nitrate on the hydration process of magnesium potassium phosphate (MKP) cement was investigated experimentally and through thermodynamic modelling using diluted systems with Mg/PO{sub 4} molar ratio and water-to-cement ratio of 1 and 100 respectively. Three processes contributed to retard cement hydration: the acidic nature of aluminum nitrate which reduced the initial pH of the solution by two units, the early precipitation of a taranakite-like amorphous potassium aluminophosphate, which reduced the aqueous phosphate and potassium concentrations, and a salt effect due to the presence of soluble nitrate. Precipitation of potassium-containing magnesium phosphate hydrates, like Mg{sub 2}KH(PO{sub 4}){sub 2}⋅15H{sub 2}O and K-struvite, was prohibited, whereas precipitation of newberyite and cattiite was delayed. Furthermore, the modelled phase development with ongoing cement hydration agreed rather well with the experimental findings.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Setting a limit on anthropogenic sources of atmospheric 81 Kr through Atom Trap Trace Analysis

In this study, we place a 2.5% limit on the anthropogenic contribution to the modern abundance of 81 Kr/Kr in the atmosphere at the 90% confidence level. Due to its simple production and transport in the terrestrial environment, 81 Kr (half-life = 230,000 years) is an ideal tracer for old water and ice with mean residence times in the range of 105–106 years. In recent years, 81 Kr-dating has been made available to the earth science community thanks to the development of Atom Trap Trace Analysis (ATTA), a laser-based atom counting technique. Further upgrades and improvements to the ATTA technique now allow us to demonstrate 81 Kr/Kr measurements with relative uncertainties of 1% and place this new limit on anthropogenic 81 Kr. As a result of this limit, we have removed a potential systematic constraint for 81 Kr-dating.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Shot noise sets the limit of quantification in electrochemical measurements

Detection of single molecules, particles, and rapid redox events is a challenge of electrochemical investigations and requires either an amplification strategy or significant averaging for the electrochemical current to exceed the noise level. We consider the minimum number of electrons required to reach the limit of quantification in these electrochemical measurements. A survey of the literature indicates that the state-of-the-art limit in current detection for different types of measurements (e.g. voltammetry, single-molecule redox cycling, ion channel recordings of single molecules, metal nanoparticle collision, and phase nucleation) is independent of the nature of the measurement and increases linearly with reciprocal response time, Δt -1 , over ~5 orders of magnitude (from ~10 to ~10 6 s -1 ). This paper demonstrates that the practical limit of quantification requires cumulative measurement of ~2100 electrons during Δt and is determined by statistics of counting electrons, that is, the shot noise in the current.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Optogenetics and biosensors set the stage for metabolic cybergenetics

We report cybergenetic systems use computer interfaces to enable feed-back controls over biological processes in real time. The complex and dynamic nature of cellular metabolism makes cybergenetics attractive for controlling engineered metabolic pathways in microbial fermentations. Cybergenetics would not only create new avenues of research into cellular metabolism, it would also enable unprecedented strategies for pathway optimization and bioreactor operation and automation. Implementation of metabolic cybergenetics, however, will require new capabilities from actuators, biosensors, and control algorithms. The recent application of optogenetics in metabolic engineering, the expanding role of genetically encoded biosensors in strain development, and continued progress in control algorithms for biological processes suggest that this technology will become available in the not so distant future.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

Advancing the theory and practice of impact assessment: Setting the research agenda

Impact assessment has been in place for over 40 years and is now practised in some form in all but two of the world's nations. In this paper we reflect on the state of the art of impact assessment theory and practice, focusing on six well-established forms: EIA, SEA, policy assessment, SIA, HIA and sustainability assessment. We note that although the fundamentals of impact assessment have their roots in the US National Environmental Policy Act 1969 (NEPA) each branch of the field is distinct in also drawing on other theoretical and conceptual bases that in turn shape the prevailing discourse in each case, generating increasing degrees of specialisation within each sub-field. Against this backdrop, we consider the strengths and weaknesses of collective impact assessment practice, concluding that although there are substantial strengths, the plethora of specialist branches is generating a somewhat confusing picture and lack of clarity regarding how the pieces of the impact assessment jigsaw puzzle fit together. We use this review to suggest an overarching research agenda that will enable impact assessment to evolve in line with changing expectations for what it should deliver. -- Highlights: ► Strengths, weakness, opportunities and threats for IA are explored in this paper ► EIA, SEA, policy assessment, SIA, HIA and sustainability assessment are reviewed ► Diversity of practice is both a strength and weakness in the current economic climate ► There are opportunities to simplify IA by focusing on common and fundamental elements ► Continued research into theory related to IA effectiveness is also essential.

54 ENVIRONMENTAL SCIENCES↗