The demand for and usage of broadband coherent mid-infrared sources, such as those provided by synchrotron facilities, are growing. Since most organic molecules exhibit characteristic vibrational modes in the wavelength range between 500 and 4000 cm, such broadband coherent sources enable micro- or even nano-spectroscopic applications at or below the diffraction limit with a high signal-to-noise ratio. These techniques have been applied in diverse fields ranging from life sciences, material analysis, and time-resolved spectroscopy. Here we demonstrate a broadband, coherent and intrinsically carrier-envelope-phase-stable source with a spectrum spanning from 500 to 2250 cm (-30 dB) at an average power of 24 mW and a repetition rate of 77 MHz. This performance is enabled by the first mode-locked thin-disk oscillator operating at 2 μm wavelength, providing a tenfold increase in average power over femtosecond oscillators previously demonstrated in this wavelength range. Multi-octave spectral coverage from this compact and power-scalable system opens up a range of time- and frequency-domain spectroscopic applications.
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http://dx.doi.org/10.1038/lsa.2017.180 | DOI Listing |
Gait initiation is a fundamental human task, requiring one or more anticipatory postural adjustments (APA) prior to stepping. Deviations in amplitude and timing of APAs exist in Parkinson's disease (PD), causing dysfunctional postural control which increases the risk of falls. The motor cortex and basal ganglia have been implicated in the regulation of postural control, however, their dynamics during gait initiation, relationship to APA metrics, and response to pharmacotherapy such as levodopa are unknown.
View Article and Find Full Text PDFThe present study employed individualized magnitudes of electroencephalographic (EEG) alpha (8-12 hz) power in the left temporal (T3) region as a neurofeedback target parameter during the aiming period in pre-elite air pistol shooters to determine its effectiveness on cerebral cortical activation and performance accuracy compared to physical skill training, only. Shooting scores and EEG activity in the left and right temporal regions were collected from 20 healthy air pistol shooters (10 assigned to neurofeedback training) before and after a 16-session intervention completed within 6 weeks. Specifically, EEG low-alpha (8-10 hz), high-alpha (10-13 hz) power, and coherence obtained at the T3-Fz and T4-Fz recording sites over three consecutive 1-s intervals prior to trigger pull, were subjected to three separate 2 × 2 × 2 × 3 (Group x Hemisphere x Time x Epoch) ANOVAs.
View Article and Find Full Text PDFNanophotonics
April 2024
National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, Jiangsu 210093, China.
Thermal emission caused by the thermal motion of the charged particles is commonly broadband, un-polarized, and incoherent, like a melting pot of electromagnetic waves, which makes it unsuitable for infrared applications in many cases requiring specific thermal emission properties. Metasurfaces, characterized by two-dimensional subwavelength artificial nanostructures, have been extensively investigated for their flexibility in tuning optical properties, which provide an ideal platform for shaping thermal emission. Recently, remarkable progress was achieved not only in tuning thermal emission in multiple degrees of freedom, such as wavelength, polarization, radiation angle, coherence, and so on but also in applications of compact and integrated optical devices.
View Article and Find Full Text PDFMultiple coherent radiations are achieved in a water-3-aminopropanol (3AP) mixed solution through cascaded four-wave mixing (C-FWM) and cascaded Stokes (C-Stokes) processes, both driven by stimulated Raman scattering (SRS) in this work. The O-H vibration peak from water is replaced by the emergence of the -NH symmetric stretching Raman peaks from 3AP, with intensity approaching that of the -CH symmetric stretching peak. The dual-wavelength SRS signals for the -NH and -CH stretching vibrations have a relatively small frequency interval of about 400 cm (16 nm).
View Article and Find Full Text PDFACS Phys Chem Au
November 2024
Rosalind Franklin Institute, Harwell OX11 0QX, Oxfordshire, United Kingdom.
Efficient photoredox chemical transformations are essential to the development of novel, cost-effective, and environmentally friendly synthetic methodologies. The concept of the entatic state in bioinorganic catalysis proposes that a preorganized structural configuration can reduce the energy barriers associated with chemical reactions. This concept provides one of the guiding principles to enhance catalytic efficiency by maintaining high-energy conformations close to the reaction's transition state.
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