Abstract. Functional near-infrared spectroscopy (fNIRS) research to date has tended to publish group-averaged rather than individual infant data due to normative basic research goals. Acquisition of individual infant time courses holds interest, however, both for cognitive science and particularly for clinical applications. Infants are more difficult to study than adults as they cannot be instructed to remain still. In addressing this, upright infants pose several associated complications for the researcher. We identified and optimized the factors that affect the quality of fNIRS data from individual 6-to 9-month-old infants exposed to a visual stimulation paradigm. The fNIRS headpiece was reconfigured to reduce inertia, increase comfort, and improve conformity to the head, while preserving fiber density to avoid missing the visual cortex activation. The visual-stimulation protocol was modified to keep the attention of infants throughout the measurement, thus helping to reduce motion artifacts. Adequate optical contact was verified by checking power levels before each measurement. By revising our experimental process and our data rejection criteria to prioritize good optical contact, we report for the first time usable hemodynamic data from 83% of infants and that two-thirds of infants produced a statistically significant fNIRS response.
Brass wind instruments with long sections of cylindrical pipe, such as trumpets and trombones, sound “brassy” when played at a fortissimo level due to the generation of a shock front in the instrument. It has been suggested that these shock fronts may increase the spread of COVID-19 by propelling respiratory particles containing the SARS-CoV-2 virus several meters due to particle entrainment in the low pressure area behind the shocks. To determine the likelihood of this occurring, fluorescent particles, ranging in size from 10–50 μm, were dropped into the shock regions produced by a trombone, a trumpet, and a shock tube. Preliminary results indicate that propagation of small airborne particles by the shock fronts radiating from brass wind instruments is unlikely.
Angular light scattering measurements have been used to determine the size parameters of spherical particles. By measuring the angular scattering from biological specimen, the average size of the cellular organelles can be estimated, which can be used to determine information about the health of the biological sample. An angular scattering microscope with the ability to be easily moved was constructed from common inexpensive components, which has potential applications for clinical and low-resource settings. The stability and accuracy of the system were investigated by measuring the scattering from polystyrene beads with mean sizes of 5 and 1.75 μm with narrow size distributions. Resulting size estimates obtained from the scattering patterns were consistent with the manufacturer-specified range of diameters for each sample. Initial studies were also conducted on individual fixed HeLa cells. The results presented indicate that the system is capable of obtaining precise and accurate size estimates of beads and single cells’ organelles.
An imaging technique is introduced that is suitable for visualizing the mode shapes of vibrating structures in an educational setting. The method produces images similar to those obtained using electronic speckle pattern interferometry (ESPI), but it can be implemented for less than 1/10 the cost of a commercial ESPI system, and the apparatus is simple enough that it can be constructed by undergraduate students. This technique allows for real-time visualization of the normal modes and deflection shapes of harmonically vibrating structures, including those with shapes that make generating Chladni patterns with sand or powder impossible. The theory of operation and construction details are discussed.
The acoustic standing wave in a transparent flue organ pipe has been imaged using high-speed transmission electronic speckle pattern interferometry. Spectral filtering of the interferograms at the acoustic resonance frequency of the gas inside the pipe results in an image showing the sinusoidal pressure dependence inside the pipe as well as the expected extension of the standing wave beyond the pipe end. However, the image also reveals anomalous and unexplained behavior as the standing wave transitions from inside to outside the pipe.
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