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Full-Text Articles in Physics
Magneto-Transport Characteristics Of A 2d Electron System Driven To Negative Magneto-Conductivity By Microwave Photoexcitation, Ramesh G. Mani, Annika Kriisa
Magneto-Transport Characteristics Of A 2d Electron System Driven To Negative Magneto-Conductivity By Microwave Photoexcitation, Ramesh G. Mani, Annika Kriisa
Physics and Astronomy Faculty Publications
Negative diagonal magneto-conductivity/resistivity is a spectacular- and thought provoking-property of driven, far-from-equilibrium, low dimensional electronic systems. The physical response of this exotic electronic state is not yet fully understood since it is rarely encountered in experiment. The microwave-radiation-induced zero-resistance state in the high mobility GaAs/AlGaAs 2D electron system is believed to be an example where negative magneto-conductivity/resistivity is responsible for the observed phenomena. Here, we examine the magneto-transport characteristics of this negative conductivity/ resistivity state in the microwave photo-excited two-dimensional electron system (2DES) through a numerical solution of the associated boundary value problem. The results suggest, surprisingly, that a bare …
Is The Brain’S Inertia For Motor Movements Different For Acceleration And Deceleration?, Bhim M. Adhikari, Kristen M. Quinn, Mukesh Dhamala
Is The Brain’S Inertia For Motor Movements Different For Acceleration And Deceleration?, Bhim M. Adhikari, Kristen M. Quinn, Mukesh Dhamala
Physics and Astronomy Faculty Publications
The brain’s ability to synchronize movements with external cues is used daily, yet neuroscience is far from a full understanding of the brain mechanisms that facilitate and set behavioral limits on these sequential performances. This functional magnetic resonance imaging (fMRI) study was designed to help understand the neural basis of behavioral performance differences on a synchronizing movement task during increasing (acceleration) and decreasing (deceleration) metronome rates. In the MRI scanner, subjects were instructed to tap their right index finger on a response box in synchrony to visual cues presented on a display screen. The tapping rate varied either continuously or …
Size-Dependent Giant-Magnetoresistance In Millimeter Scale Gaas/Algaas 2d Electron Devices, Ramesh G. Mani, Annika Kriisa, Werner Wegscheider
Size-Dependent Giant-Magnetoresistance In Millimeter Scale Gaas/Algaas 2d Electron Devices, Ramesh G. Mani, Annika Kriisa, Werner Wegscheider
Physics and Astronomy Faculty Publications
Large changes in the electrical resistance induced by the application of a small magnetic field are potentially useful for device-applications. Such Giant Magneto-Resistance (GMR) effects also provide new insights into the physical phenomena involved in the associated electronic transport. This study examines a ‘‘bell-shape’’ negative GMR that grows inmagnitude with decreasing temperatures inmm-wide devices fabricated from the high-mobility GaAs/AlGaAs 2-Dimensional Electron System (2DES). Experiments show that the span of this magnetoresistance on the magnetic-field-axis increases with decreasing device width, W, while there is no concurrent Hall resistance, Rxy, correction. A multi-conduction model, including negative diagonalconductivity, and non-vanishing off-diagonal conductivity, reproduces …
Comparison Of Calculated And Experimental Isotope Edited Ftir Difference Spectra For Purple Bacterial Photosynthetic Reaction Centers With Different Quinones Incorporated Into The Qa Binding Site, Nan Zhao, Hari Prasad Lamichhane, Gary Hastings
Comparison Of Calculated And Experimental Isotope Edited Ftir Difference Spectra For Purple Bacterial Photosynthetic Reaction Centers With Different Quinones Incorporated Into The Qa Binding Site, Nan Zhao, Hari Prasad Lamichhane, Gary Hastings
Physics and Astronomy Faculty Publications
Previously we have shown that ONIOM type (QM/MM) calculations can be used to simulate isotope edited FTIR difference spectra for neutral ubiquinone in the QA binding site in Rhodobacter sphaeroides photosynthetic reaction centers. Here we considerably extend upon this previous work by calculating isotope edited FTIR difference spectra for reaction centers with a variety of unlabeled and 18 O labeled foreign quinones incorporated into the QA binding site. Isotope edited spectra were calculated for reaction centers with 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone (MQ0 ), 2,3,5,6-tetramethyl-1, 4-benzoquinone (duroquinone, DQ), and 2,3-dimethyl-l,4-naphthoquinone (DMNQ) incorporated, and compared to corresponding experimental spectra. The calculated and experimental spectra agree …
Higher Frequency Network Activity Flow Predicts Lower Frequency Node Activity In Intrinsic Low-Frequency Bold Fluctuations, Sahil Bajaj, Bhim M. Adhikari, Mukesh Dhamala
Higher Frequency Network Activity Flow Predicts Lower Frequency Node Activity In Intrinsic Low-Frequency Bold Fluctuations, Sahil Bajaj, Bhim M. Adhikari, Mukesh Dhamala
Physics and Astronomy Faculty Publications
The brain remains electrically and metabolically active during resting conditions. The low-frequency oscillations (LFO) of the blood oxygen level-dependent (BOLD) signal of functional magnetic resonance imaging (fMRI) coherent across distributed brain regions are known to exhibit features of this activity. However, these intrinsic oscillations may undergo dynamic changes in time scales of seconds to minutes during resting conditions. Here, using wavelet-transform based timefrequency analysis techniques, we investigated the dynamic nature of default-mode networks from intrinsic BOLD signals recorded from participants maintaining visual fixation during resting conditions. We focused on the default-mode network consisting of the posterior cingulate cortex (PCC), the …
Calculated Vibrational Properties Of Ubisemiquinones, Hari P. Lamichhane, Gary Hastings
Calculated Vibrational Properties Of Ubisemiquinones, Hari P. Lamichhane, Gary Hastings
Physics and Astronomy Faculty Publications
Density functional theory has been used to calculate harmonic normal mode vibrational frequencies for unlabeled and isotopelabeled ubisemiquinones in both the gas phase and in several solvents. It is shown that four methoxy group conformations are likely to be present in solution at room temperature. Boltzmann weighted infrared and Raman spectra for the four conformers were calculated, and composite spectra that are the sum of the Boltzmann weighted spectra were produced. These composite spectra were compared to experimental FTIR and resonance Raman spectra, and it is shown that the calculated band frequencies, relative band intensities, and 13C and 18 …