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Karlsson, Anna

Publications and source records attributed to Karlsson, Anna.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

The Roles of Nicotinamide Adenine Dinucleotide Phosphate Reoxidation and Ammonium Assimilation in the Secretion of Amino Acids as Byproducts of Clostridium thermocellum

Improving the ethanol yield of C. thermocellum is important for the industrial implementation of this microorganism in consolidated bioprocessing. A central role of NADPH in driving amino acid byproduct formation was demonstrated by eliminating the NADPH-supplying malate shunt and separately by changing the cofactor specificity in ammonium assimilation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Theory of collective magnetophonon resonance and melting of a field-induced Wigner solid

Electron solid phases of matter are revealed by characteristic vibrational resonances. Sufficiently large magnetic fields can overcome the effects of disorder, leading to a weakly pinned collective mode called the magnetophonon. Consequently, in this regime it is possible to develop a tightly constrained hydrodynamic theory of pinned magnetophonons. Here, the behavior of the magnetophonon resonance across thermal and quantum melting transitions has been experimentally characterized in two-dimensional electron systems. Applying our theory to these transitions we explain several key features of the data. Firstly, violation of the Fukuyama-Lee sum rule as the transition is approached is shown to be a consequence of the non-Lorentzian form taken by the resonance. Secondly, this non-Lorentzian shape is shown to be caused by dissipative channels that become especially important close to melting: proliferating dislocations and uncondensed charge carriers.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Bad Metals from Fluctuating Density Waves

Bad metals have a large resistivity without being strongly disordered. In many bad metals the Drude peak moves away from zero frequency as the resistivity becomes large at increasing temperatures. We catalogue the position and width of the ‘displaced Drude peak’ in the observed optical conductivity of several families of bad metals, showing that \omega_\text{peak} \sim \Delta \omega \sim k_BT/\hbar ω peak ∼ Δ ω ∼ k B T / ℏ . This is the same quantum critical timescale that underpins the T T -linear dc resistivity of many of these materials. We provide a unified theoretical description of the optical and dc transport properties of bad metals in terms of the hydrodynamics of short range quantum critical fluctuations of incommensurate density wave order. Within hydrodynamics, pinned translational order is essential to obtain the nonzero frequency peak.

Delacrétaz, Luca↗