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To explore resonance phenomena in the nonlinear region, we show by experimental measurements and theoretical analyses that resonance happens in modulation instability from non-instantaneous nonlinearities in photorefractive crystals. With a temporally periodic modulation in the external bias voltage, corresponding to a modulation in the nonlinear strength, an enhancement in the visibility of MI at resonant frequency is reported through spontaneous optical pattern formations. Theoretical curves obtained from a nonlinear non-instantaneous Schrödinger equation give good agreement to experimental data.
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http://dx.doi.org/10.1364/OL.43.003329 | DOI Listing |
ACS Appl Mater Interfaces
September 2025
Department of Chemical Engineering, Keimyung University, Daegu 42601, Republic of Korea.
Indium tin oxide (Sn/InO) is a degenerately doped semiconductor nanocrystal (NC) that exhibits localized surface plasmon resonance (LSPR) in the short-wavelength infrared electromagnetic spectral range. Alternative to metals, the tunability of LSPR is possible in doped semiconductor NCs by controlling the dopant type, doping level, and opto-electrochemical modulation. In this study, dopant oxidation valency in carrier density and LSPR peaks (Sn(IV): 1.
View Article and Find Full Text PDFMAGMA
September 2025
Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan 100, 3585CX, Utrecht, The Netherlands.
Objective: Within gradient-spoiled transient-state MR sequences like Magnetic Resonance Fingerprinting or Magnetic Resonance Spin TomogrAphy in Time-domain (MR-STAT), it is examined whether an optimized RF phase modulation can help to improve the precision of the resulting relaxometry maps.
Methods: Using a Cramer-Rao based method called BLAKJac, optimized sequences of RF pulses have been generated for two scenarios (amplitude-only modulation and amplitude + phase modulation) and for several conditions. These sequences have been tested on a phantom, a healthy human brain and a healthy human leg, to reconstruct parametric maps ( and ) as well as their standard deviations.
Biol Cybern
September 2025
School of Electrical and Information Engineering, Tianjin University, Tianjin, 300072, China.
Correlated spiking has been widely found in large population of neurons and been linked to neural coding. Transcranial alternating current stimulation (tACS) is a promising non-invasive brain stimulation technique that can modulate the spiking activity of neurons. Despite its growing application, the tACS effects on the temporal correlation between spike trains are still not fully understood.
View Article and Find Full Text PDFNat Nanotechnol
September 2025
School of Engineering, The University of Tokyo, Tokyo, Japan.
Active metasurfaces incorporating electro-optic materials enable high-speed free-space optical modulators that show great promise for a wide range of applications, including optical communication, sensing and computing. However, the limited light-matter interaction lengths in metasurfaces typically require high driving voltages exceeding tens of volts to achieve satisfactory modulation. Here we present low-voltage, high-speed free-space optical modulators based on silicon-organic-hybrid metasurfaces with dimerized-grating-based nanostructures.
View Article and Find Full Text PDFBrain Res Bull
September 2025
Department of Psychiatry, Keck School of Medicine, University of Southern California, Los Angeles, CA; Institute for the Developing Mind, Children's Hospital Los Angeles, Los Angeles, CA.
We propose a Biophysically Restrained Analog Integrated Neural Network (BRAINN), an analog electrical network that models the dynamics of brain function. The network interconnects analog electrical circuits that simulate two tightly coupled brain processes: (1) propagation of an action potential, and (2) regional cerebral blood flow in response to the metabolic demands of signal propagation. These two processes are modeled by two branches of an electrical circuit comprising a resistor, a capacitor, and an inductor.
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