Rapid measurement of sake mash using differential near-infrared spectra of diffuse transmission and transflectance.

Currently, various sake brewers employ data-driven approaches to ensure the stable production and supply of high-quality products. This study aimed to develop a novel direct measurement system using near-infrared (NIR) spectroscopy to monitor the fermentation process of sake mash during brewing. Direct measurement of sake mash has been challenging because of the significant absorption bands of water and the impact of physical properties such as multiple scattering within the mash. To address these challenges, we propose the subtraction of spectra, called differential reflectance, obtained through two measurement methods, namely, diffuse reflection and transflectance, to reduce the impact of physical properties. This approach includes limiting the wavelength range from 400 to 1300 nm, utilizing the second derivative in the Savitzky-Golay method, and applying multiplicative scatter correction (MSC) to the entire wavelength. When partial least squares regression (PLS-R) was applied, the root mean square error for predicting (RMSEP) alcohol concentration in the model sake mash sample (14.65-18.41 % v/v) was 0.33 % v/v. Finally, as a practical experiment, alcohol concentrations in the actual mash (0.00-17.49 % v/v) were predicted with differential reflectance spectra by MSC. The resulting RMSEP value was 0.76 % v/v, a significant improvement of 1.99 % v/v predicted by diffuse reflectance. These findings demonstrate the effectiveness of the proposed spectral subtraction method as a new direct measurement approach for monitoring sake fermentation in sake mash.

A two-stage spectral model for sound texture perception: Synthesis and psychophysics.

The natural environment is filled with a variety of auditory events such as wind blowing, water flowing, and fire crackling. It has been suggested that the perception of such textural sounds is based on the statistics of the natural auditory events. Inspired by a recent spectral model for visual texture perception, we propose a model that can describe the perceived sound texture only with the linear spectrum and the energy spectrum. We tested the validity of the model by using synthetic noise sounds that preserve the two-stage amplitude spectra of the original sound. Psychophysical experiment showed that our synthetic noises were perceived as like the original sounds for 120 real-world auditory events. The performance was comparable with the synthetic sounds produced by McDermott-Simoncelli's model which considers various classes of auditory statistics. The results support the notion that the perception of natural sound textures is predictable by the two-stage spectral signals.

Spatial attention in perceptual decision making as revealed by response-locked classification image analysis.

In many situations, humans serially sample information from many locations in an image to make an appropriate decision about a visual target. Spatial attention and eye movements play a crucial role in this serial vision process. To investigate the effect of spatial attention in such dynamic decision making, we applied a classification image (CI) analysis locked to the observer's reaction time (RT). We asked human observers to detect as rapidly as possible a target whose contrast gradually increased on the left or right side of dynamic noise, with the presentation of a spatial cue. The analysis revealed a spatiotemporally biphasic profile of the CI which peaked at ~ 350 ms before the observer's response. We found that a valid cue presented at the target location shortened the RT and increased the overall amplitude of the CI, especially when the cue appeared 500-1250 ms before the observer's response. The results were quantitatively accounted for by a simple perceptual decision mechanism that accumulates the outputs of the spatiotemporal contrast detector, whose gain is increased by sustained attention to the cued location.

Response-locked classification image analysis of perceptual decision making in contrast detection.

In many situations, humans make decisions based on serially sampled information through the observation of visual stimuli. To quantify the critical information used by the observer in such dynamic decision making, we here applied a classification image (CI) analysis locked to the observer's reaction time (RT) in a simple detection task for a luminance target that gradually appeared in dynamic noise. We found that the response-locked CI shows a spatiotemporally biphasic weighting profile that peaked about 300 ms before the response, but this profile substantially varied depending on RT; positive weights dominated at short RTs and negative weights at long RTs. We show that these diverse results are explained by a simple perceptual decision mechanism that accumulates the output of the perceptual process as modelled by a spatiotemporal contrast detector. We discuss possible applications and the limitations of the response-locked CI analysis.

Visualization of myelinated fiber bundles orientation during brain slice preparation by reflection polarized light microscopy.

Polarized light imaging (PLI) enables detecting the orientation of myelinated axon bundles in brain slices at microscopic resolution without histological staining. However, standard PLI requires labor-intensive procedures such as mounting brain cryosections on slide glasses. We developed an optical system that does not require a mounting procedure for PLI. Specifically, we developed an optical system to perform PLI in reflection mode (rPLI) instead of employing transmitted light as in standard PLI. We integrated this rPLI system with a conventional vibratome slicer whose cutting blade surface is a mirror. This combination allowed PLI measurements directly during the slicing procedure at room temperature. Thus, mounting procedure for PLI is not necessary. As a proof-of-concept experiment, a perfusion-fixed brain of a mouse was embedded in gelatin-containing agar and cut serially at 40~200 µm intervals. The slicing procedure was temporarily halted after each cut to capture the PLI images of the slice on the reflecting blade surface while the slice was still held up by the agar block. The orientation of the fiber bundle estimated with this method agreed with the results obtained from previous reports. Combination of a popular vibratome slicer and our rPLI system that uses versatile and inexpensive optical components would increase popularity of PLI and facilitates connectome studies at microscopic resolution. RESEARCH HIGHLIGHTS: Polarized light imaging (PLI) of brain slices was realized by using reflected light (rPLI) instead of transmitted light. The rPLI method allows detecting the myelinated fiber bundle orientation during slice preparation.

Regulatory phosphorylation of poly-γ-glutamic acid with phosphate salts in the culture of Bacillus subtilis (natto).

Poly-γ-glutamic acid (PGA) was easily phosphorylated by direct addition of phosphorylating agents into the culture medium of Bacillus subtilis (natto). Tetrapolyphosphate salt was the most incorporated into PGA molecules of all used reagents. Phosphorylation occurred at the α-carboxyl side chains of PGA molecule. The amounts of bound phosphate to PGA were dependent on the amounts of added phosphorylating agent. In low molecular weight regions of less than 100 kDa, a cross-linked peak was observed in the phosphorylated PGAs, whereas their peaks at approximately 1000 kDa shifted to a higher molecular weight due to the bound phosphate. The PGA derivatives had a wide range in viscosity up to 15/1000 to 15 times when compared to the native PGA, depending on the degree of phosphorylation (DP) in the PGA derivatives. The PGA with low DP had a high viscosity due to the unfolding conformation whereas highly phosphorylated PGA had aggregation with low viscosity. Heat treatment at 80 °C after the addition of phosphate salt elicited a novel collagen-like helix structure. These observations show that phosphorylation is an effective way to diversify the physicochemical properties of PGA.

The ergosterol biosynthesis inhibitor zaragozic acid promotes vacuolar degradation of the tryptophan permease Tat2p in yeast.

Ergosterol is the yeast functional equivalent of cholesterol in mammalian cells. Deletion of the ERG6 gene, which encodes an enzyme catalyzing a late step of ergosterol biosynthesis, impedes targeting of the tryptophan permease Tat2p to the plasma membrane, but does not promote vacuolar degradation. It is unknown whether similar features appear when other steps of ergosterol biogenesis are inhibited. We show herein that the ergosterol biosynthesis inhibitor zaragozic acid (ZA) evoked massive vacuolar degradation of Tat2p, accompanied by a decrease in tryptophan uptake. ZA inhibits squalene synthetase (SQS, EC 2.5.1.21), which catalyzes the first committed step in the formation of cholesterol/ergosterol. The degradation of Tat2p was dependent on the Rsp5p-mediated ubiquitination of Tat2p and was not suppressed by deletions of VPS1, VPS27, VPS45 or PEP12. We will discuss ZA-mediated Tat2p degradation in the context of lipid rafts.

TOR regulates late steps of ribosome maturation in the nucleoplasm via Nog1 in response to nutrients.

The protein kinase TOR (target of rapamycin) controls several steps of ribosome biogenesis, including gene expression of rRNA and ribosomal proteins, and processing of the 35S rRNA precursor, in the budding yeast Saccharomyces cerevisiae. Here we show that TOR also regulates late stages of ribosome maturation in the nucleoplasm via the nuclear GTP-binding protein Nog1. Nog1 formed a complex that included 60S ribosomal proteins and pre-ribosomal proteins Nop7 and Rlp24. The Nog1 complex shuttled between the nucleolus and the nucleoplasm for ribosome biogenesis, but it was tethered to the nucleolus by both nutrient depletion and TOR inactivation, causing cessation of the late stages of ribosome biogenesis. Furthermore, after this, Nog1 and Nop7 proteins were lost, leading to complete cessation of ribosome maturation. Thus, the Nog1 complex is a critical regulator of ribosome biogenesis mediated by TOR. This is the first description of a physiological regulation of nucleolus-to-nucleoplasm translocation of pre-ribosome complexes.