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Full-Text Articles in Physics
Atomic-Scale Diffractive Imaging Of Sub-Cycle Electron Dynamics In Condensed Matter, Vladislav S. Yakovlev, Mark I. Stockman, Ferenc Krausz, Peter Baum
Atomic-Scale Diffractive Imaging Of Sub-Cycle Electron Dynamics In Condensed Matter, Vladislav S. Yakovlev, Mark I. Stockman, Ferenc Krausz, Peter Baum
Physics and Astronomy Faculty Publications
For interaction of light with condensed-matter systems, we show with simulations that ultrafast electron and X-ray diffraction can provide a time-dependent record of charge-density maps with sub-cycle and atomic-scale resolutions. Using graphene as an example material, we predict that diffraction can reveal localised atomic-scale origins of optical and electronic phenomena. In particular, we point out nontrivial relations between microscopic electric current and density in undoped graphene.
Control Of Plasmonic Nanoantennas By Reversible Metal-Insulator Transition, Yohannes Abate, Robert E. Marvel, Jed I. Ziegler, Sampath Gamage, Mohammad H. Javani, Mark I. Stockman, Richard F. Haglund
Control Of Plasmonic Nanoantennas By Reversible Metal-Insulator Transition, Yohannes Abate, Robert E. Marvel, Jed I. Ziegler, Sampath Gamage, Mohammad H. Javani, Mark I. Stockman, Richard F. Haglund
Physics and Astronomy Faculty Publications
We demonstrate dynamic reversible switching of VO2 insulator-to-metal transition (IMT) locally on the scale of 15 nm or less and control of nanoantennas, observed for the first time in the near-field. Using polarization-selective near-field imaging techniques, we simultaneously monitor the IMT in VO2 and the change of plasmons on gold infrared nanoantennas. Structured nanodomains of the metallic VO2 locally and reversibly transform infrared plasmonic dipole nanoantennas to monopole nanoantennas. Fundamentally, the IMT in VO2 can be triggered on femtosecond timescale to allow ultrafast nanoscale control of optical phenomena. These unique features open up promising novel applications in active nanophotonics.
Brain Effective Connectivity During Motor-Imagery And Execution Following Stroke And Rehabilitation, Sahil Bajaj, Andrew Butler, Daniel Drake, Mukesh Dhamala
Brain Effective Connectivity During Motor-Imagery And Execution Following Stroke And Rehabilitation, Sahil Bajaj, Andrew Butler, Daniel Drake, Mukesh Dhamala
Physics and Astronomy Faculty Publications
Brain areas within the motor system interact directly or indirectly during motor-imagery and motor-execution tasks. These interactions and their functionality can change following stroke and recovery. How brain network interactions reorganize and recover their functionality during recovery and treatment following stroke are not well understood. To contribute to answering these questions, we recorded blood oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI) signals from10 stroke survivors and evaluated dynamical causal modeling (DCM)-based effective connectivity among three motor areas: primary motor cortex (M1), premotor cortex (PMC) and supplementary motor area (SMA), during motor-imagery and motor-execution tasks. We compared the connectivity between …
Functional Organization And Restoration Of The Brain Motor-Execution Network After Stroke And Rehabilitation, Sahil Bajaj, Andrew Butler, Daniel Drake, Mukesh Dhamala
Functional Organization And Restoration Of The Brain Motor-Execution Network After Stroke And Rehabilitation, Sahil Bajaj, Andrew Butler, Daniel Drake, Mukesh Dhamala
Physics and Astronomy Faculty Publications
Multiple cortical areas of the human brain motor system interact coherently in the low frequency range (<0.1 Hz), even in the absence of explicit tasks. Following stroke, cortical interactions are functionally disturbed. How these interactions are affected and how the functional organization is regained from rehabilitative treatments as people begin to recover motor behaviors has not been systematically studied. We recorded the intrinsic functional magnetic resonance imaging (fMRI) signals from 30 participants: 17 young healthy controls and 13 aged stroke survivors. Stroke participants underwent mental practice (MP) or both mental practice and physical therapy (MP+PT) within 14–51 days following stroke. We investigated the network activity of five core areas in the motor-execution network, consisting of the left primary motor area (LM1), the right primary motor area (RM1), the left pre-motor cortex (LPMC), the right pre-motor cortex (RPMC) and the supplementary motor area (SMA). We discovered that (i) the network activity dominated in the frequency range 0.06–0.08 Hz for all the regions, and for both able-bodied and stroke participants (ii) the causal information flow between the regions: LM1 and SMA, RPMC and SMA, RPMC and LM1, SMA and RM1, SMA and LPMC, was reduced significantly for stroke survivors (iii) the flow did not increase significantly after MP alone and (iv) the flow among the regions during MP+PT increased significantly. We also found that sensation and motor scores were significantly higher and correlated with directed functional connectivity measures when the stroke-survivors underwent MP+PT but not MP alone. The findings provide evidence that a combination of mental practice and physical therapy can be an effective means of treatment for stroke survivors to recover or regain the strength of motor behaviors, and that the spectra of causal information flow can be used as a reliable biomarker for evaluating rehabilitation in stroke survivors.
Vibrational Spectroscopy Of Photosystem I, Gary Hastings
Vibrational Spectroscopy Of Photosystem I, Gary Hastings
Physics and Astronomy Faculty Publications
Fourier transform infrared difference spectroscopy (FTIR DS) has beenwidely used to study the structural details of electron transfer cofactors (and their binding sites) in many types of photosynthetic protein complexes. This review focuses in particular onwork that has been done to investigate the A1 cofactor in photosystemI photosynthetic reaction centers. A reviewof this subject area last appeared in 2006 [1], so onlywork undertaken since then will be covered here. Following light excitation of intact photosystem I particles the P700+A1 \ secondary radical pair state is formed within 100 ps. This state decays within 300 ns at room temperature, or 300 …