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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Discovery of 2-Pyridinone Aminals: A Prodrug Strategy to Advance a Second Generation of HIV-1 Integrase Strand Transfer Inhibitors

The search for new molecular constructs that resemble the critical two-metal binding pharmacophore required for HIV integrase strand transfer inhibition represents a vibrant area of research within drug discovery. Here we present the discovery of a new class of HIV integrase strand transfer inhibitors based on the 2-pyridinone core of MK-0536. These efforts led to the identification of two lead compounds with excellent antiviral activity and preclinical pharmacokinetic profiles to support a once-daily human dose prediction. Dose escalating PK studies in dog revealed significant issues with limited oral absorption and required an innovative prodrug strategy to enhance the high-dose plasma exposures of the parent molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Probing High-Temperature Amine Chemistry: Is the Reaction NH 3 + NH 2 ⇌ N 2 H 3 + H 2 Important?

The reaction NH 3 + NH 2 ⇌ N 2 H 3 + H 2 (R1) has been identified as a key step to explain experimental results for pyrolysis and oxidation of ammonia. However, no direct experimental or theoretical evidence for the reaction has been reported. In the present work, the reaction was studied by ab initio theory and by reinterpretation of experimental data. We could not locate a transition state for R1 occurring as a direct process, but alternative mechanisms yielded an upper bound to k 1 of 1.5 × 10 13 exp(–58.9 kcal mol –1 /RT) cm 3 mol –1 s –1 over 1000–2500 K, several orders of magnitude lower than values applied in modeling. Consistent with the theoretical work, re-evaluation of NH 3 pyrolysis data supported a very low value of k 1 . However, this finding opens up a novel unresolved issue. Current kinetic models cannot capture the NH 3 oxidation behavior in a number of laminar flow reactor and jet-stirred reactor experiments without adopting an improbably high value for k 1 . Furthermore, important oxidation steps might be underestimated or missing from mechanisms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Product Detection of the CH Radical Reactions with Ammonia and Methyl-Substituted Amines

In this work, reactions of the methylidyne (CH) radical with ammonia (NH 3 ), methylamine (CH 3 NH 2 ), dimethylamine ((CH 3 ) 2 NH), and trimethylamine ((CH 3 ) 3 N) have been investigated under multiple collision conditions at 373 K and 4 Torr. The reaction products are detected by using soft photoionization coupled to orthogonal acceleration time-of-flight mass spectrometry at the Advanced Light Source (ALS) synchrotron. Kinetic traces are employed to discriminate between CH reaction products and products from secondary or slower reactions. Branching ratios for isomers produced at a given mass and formed by a single reaction are obtained by fitting the observed photoionization spectra to linear combinations of pure compound spectra. The reaction of the CH radical with ammonia is found to form mainly imine, HN$=$CH 2 , in line with an addition–elimination mechanism. The singly methyl-substituted imine is detected for the CH reactions with methylamine, dimethylamine, and trimethylamine. Dimethylimine isomers are formed by the reaction of CH with dimethylamine, while trimethylimine is formed by the CH reaction with trimethylamine. Overall, the temporal profiles of the products are not consistent with the formation of aminocarbene products in the reaction flow tube. In the case of the reactions with methylamine and dimethylamine, product formation is assigned to an addition–elimination mechanism similar to that proposed for the CH reaction with ammonia. However, this mechanism cannot explain the products detected by the reaction with trimethylamine. A C—H insertion pathway may become more probable as the number of methyl groups increases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Promotion of CaCO 3 Nucleation by Carboxyl- and Amine-Terminated Peptoid Nanotubes

The use of surfaces to promote heterogeneous nucleation of CaCO 3 has been extensively studied to better understand natural processes of biomineralization, to develop bioinspired approaches for synthesizing composite materials with diverse functionalities, and as a route toward accelerating CO 2 mineralization. Peptoids have emerged as a material of particular interest, because they offer tunable side chain chemistry while maintaining a constant long-range self-assembled architecture. Here, in this work, we investigate the ability of films of self-assembled -NH 2 and −COOH terminated peptoid nanotubes to promote the nucleation of CaCO 3 . Using a combination of atomic force, scanning electron, and optical microscopy, we find that interwoven films of nanotubes formed from peptoids with -NH 2 side chains promote the preferential formation of vaterite with the (001) plane parallel to the film and exhibit a lower interfacial energy than that reported for inorganic surfaces. In contrast, the film of −COOH-functionalized peptoid nanotubes is a much stronger promoter, giving a particle density 5 orders of magnitude larger than for the -NH 2 terminated peptoid nanotubes and enabling complete coverage of individual peptoid tubes with CaCO 3 nanoparticles that results in a composite material with a 50-fold increase in Young’s modulus. Thus, interwoven films of peptoid nanotubes provide a useful platform for investigating the impact of specific chemical groups on nucleation and offer potential application to accelerated mineralization of CO 2 for removal from the environment or modulation of mineralogy and properties of carbonate-based building materials.

carbon nanotubes↗
DOE OSTI2017

Supercharging a MnO 2 Nanowire: An Amine-Altered Morphology Retains Capacity at High Rates and Mass Loadings

The influence of hexamethylenetetraamine (HMTA) on the morphology of $δ$-MnO 2 and its properties for electrical energy storage are investigated—specifically for ultrathick $δ$-MnO 2 layers in the micron scale. Planar arrays of gold@$δ$-MnO 2 , core@shell nanowires, were prepared by electrodeposition with and without the HMTA and their electrochemical properties were evaluated. HMTA alters the MnO 2 in three ways: First, it creates a more open morphology for the MnO 2 coating, characterized by “petals” with a thickness of 6 to 9 nm, rather than much thinner $δ$-MnO 2 sheets seen in the absence of HMTA. Second, the electronic conductivity of the $δ$-MnO 2 is increased by an order of magnitude. Third, $δ$-MnO 2 prepared in HMTA shows a (001) interlayer spacing that is expanded by ≈30% possibly accelerating Li transport. The net effect of “HTMA doping” is to dramatically improve high rate performance, culminating in an increase in the specific capacity for the thickest MnO 2 shells examined here by a factor of 15 at 100 mV/s.

36 MATERIALS SCIENCE↗