Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “POSITRON”

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.

At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Synthesis, radiolabeling, and biological evaluation of ( R )- and ( S )-2-amino-5-[ 18 F]fluoro-2-methylpentanoic acid (( R )-, ( S )-[ 18 F]FAMPe) as potential positron emission tomography tracers for brain tumors

In this paper, a novel 18 F-labeled α,α-disubstituted amino acid-based tracer, 2-amino-5-[ 18 F]fluoro-2-methylpentanoic acid ([ 18 F]FAMPe), has been developed for brain tumor imaging with a longer alkyl side chain than previously reported compounds to increase brain availability via system L amino acid transport. Both enantiomers of [ 18 F]FAMPe were obtained in good radiochemical yield (24–52% n = 8) and high radiochemical purity (>99%). In vitro uptake assays in mouse DBT gliomas cells revealed that ( S )-[ 18 F]FAMPe enters cells partly via sodium-independent system L transporters and also via other nonsystem A transport systems including transporters that recognize glutamine. Biodistribution and small animal PET/CT studies in the mouse DBT model of glioblastoma showed that both ( R )- and ( S )-[ 18 F]FAMPe have good tumor imaging properties with the ( S )-enantiomer providing higher tumor uptake and tumor to brain ratios. Finally, comparison of the SUVs showed that ( S )-[ 18 F]FAMPe had higher tumor to brain ratios compared to ( S )-[ 18 F]FET, a well-established system L substrate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Collective plasma effects of electron–positron pairs in beam-driven QED cascades

Understanding the interplay of strong-field QED and collective plasma effects is important for explaining extreme astrophysical environments like magnetars. It has been shown that QED pair plasma can be produced and observed by passing a relativistic electron beam through an intense laser field. This work presents in detail multiple sets of 3D QED-particle-in-cell simulations to show the creation of pair plasma in the QED cascade. The beam driven method enables a high pair particle density and also a low particle Lorentz factor, which both play equal roles on exhibiting large collective plasma effects. Finite laser frequency upshift is observed with both ideal parameters (24 PW laser colliding with a 300 GeV electron beam) and with existing technologies (3 PW laser colliding with a 30 GeV electron beam).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗