Spatial distribution multimedia fate model: Numerical aspects and ability for spatial analysis

A spatial distribution multimedia fate model is proposed for the rigorous simulation of the environmental multimedia fate of hazardous chemicals emitted from a variety of sources. To solve the relevant equation, we introduce an explicit finite difference method applied to uniform grids. We assessed the numerical properties of the model, including stability and accuracy. A new dimensionless number (multimedia transport number) is proposed for determining the numerical stability of the unsteady-state method. The model was verified by comparison with analytical solutions for the transport of non-conservative substances in two-phase open-channel flow. The spatial resolution of the spatial distribution model was tested via a comparison with a general multimedia fate model in a practical application related to toluene emissions in Seoul, South Korea.     

Characteristics of Rubber/Sodium Montmorillonite Nanocomposites Prepared by a Novel Method

In order to enhance the fine dispersion of hydrophilic sodium montmorillonite (Na‐MMT) in the matrix of hydrophobic rubber, the hydrophobic modification of Na‐MMT was carried out via an in situ method in the melt compounding process using the modifiers poly(ethylene glycol) monooleate or poly(ethylene glycol) diacrylate, both of which have a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic hydrocarbon segment. The X‐ray diffraction patterns showed that the interlayer distance of Na‐MMT was expanded by the intercalation of these modifiers. The morphology observed by scanning electron microscopy as well as the cure characteristics and tensile modulus showed that this organic modification effectively enhanced the fine dispersion of Na‐MMT in the rubber matrix.     

Characterization of fish schooling behavior with different numbers of Medaka (Oryzias latipes) and goldfish (Carassius auratus) using a Hidden Markov Model

Fish that swim in schools benefit from increased vigilance, and improved predator recognition and assessment. Fish school size varies according to species and environmental conditions. In this study, we present a Hidden Markov Model (HMM) that we use to characterize fish schooling behavior in different sized schools, and explore how school size affects schooling behavior. We recorded the schooling behavior of Medaka (Oryzias latipes) and goldfish (Carassius auratus  ) using different numbers of individual fish (10–40), in a circular aquarium. Eight to ten 3 s video clips were extracted from the recordings for each group size. Schooling behavior was characterized by three variables: linear speed, angular speed, and Pearson coefficient. The values of the variables were categorized into two events each for linear and angular speed (high and low), and three events for the Pearson coefficient (high, medium, and low). Schooling behavior was then described as a sequence of 12 events (2×2×3$2\times 2\times 3$), which was input to an HMM as data for training the model. Comparisons of model output with observations of actual schooling behavior demonstrated that the HMM was successful in characterizing fish schooling behavior. We briefly discuss possible applications of the HMM for recognition of fish species in a school, and for developing bio-monitoring systems to determine water quality.     

4 × 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Abstract

Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.     

Effectively controlled microfluidic trap for spatiotemporal analysis of the electrotaxis of Caenorhabditis elegans

C. elegans is a popular model organism with a well‐developed neural network. Approximately 60% of the genes in C. elegans have genomic counterparts in humans, including those involved in building neural circuits. Therefore, we can extend the study of human neural network mechanisms to C. elegans which is easy to genetically manipulate. C. elegans shows behavioural responses to various external physical and chemical stimuli. Electrotaxis is one of its distinct behavioural responses, which is defined as movement towards the cathode in an electric field. In this study, we developed an effective microfluidic trap system for analysing electrotaxis in C. elegans. In addition, two mutant strains (unc‐54(s74) and unc‐6(e78)) from wild‐type (N2) worms were screened using the system. Wild‐type (N2) worms and the two mutant strains clearly showed different behavioural responses to the applied electric field, thus enabling the effective screening of the mutant worms from the wild type (N2). This microfluidic system can be utilized as a platform for the study of behavioural responses, and for the sorting and mutant screening of C. elegans.     

Preparation of poly(?-caprolactone)-based polyurethane nanofibers containing silver nanoparticles

In this study, poly(?-caprolactone)-based polyurethane (PCL-PU) nanofibers containing Ag nanoparticles for use in antimicrobial nanofilter applications were prepared by electrospinning 8 wt% PCL-PU solutions containing different amounts of AgNO₃ in a mixed solvent consisting of DMF/THF (7/3 w/w). The average diameter of the pure PCL-PU nanofibers was 560 nm and decreased with increasing concentration of AgNO₃. The PCL-PU nanofiber mats electrospun with AgNO₃ exhibited higher tensile strength, tensile modulus, and lower elongation than the pure PCL-PU nanofiber mats. Small Ag nanoparticles were produced by the reduction of Ag⁺ ions in the PCL-PU solutions. The average size and number of the Ag nanoparticles in the PCL-PU nanofibers were considerably increased after being annealed at 100 °C for 24 h. They were all sphere-shaped and evenly distributed in the PCL-PU nanofibers, indicating that the PCL-PU chains stabilized the Ag nanoparticles well.     

The effect of visual and auditory cues on seat preference in an opera theater

Opera performance conveys both visual and auditory information to an audience, and so opera theaters should be evaluated in both domains. This study investigates the effect of static visual and auditory cues on seat preference in an opera theater. Acoustical parameters were measured and visibility was analyzed for nine seats. Subjective assessments for visual-only, auditory-only, and auditory-visual preferences for these seat positions were made through paired-comparison tests. In the cases of visual-only and auditory-only subjective evaluations, preference judgment tests on a rating scale were also employed. Visual stimuli were based on still photographs, and auditory stimuli were based on binaural impulse responses convolved with a solo tenor recording. For the visual-only experiment, preference is predicted well by measurements taken related to the angle of seats from the theater midline at the center of the stage, the size of the photographed stage view, the visual obstruction, and the distance from the stage. Sound pressure level was the dominant predictor of auditory preference in the auditory-only experiment. In the cross-modal experiments, both auditory and visual preferences were shown to contribute to overall impression, but auditory cues were more influential than the static visual cues. The results show that both a positive visual-only or a positive auditory-only evaluations positively contribute to the assessments of seat quality.     

Reversible Transformation between Cubane and Stairstep Cu4I4 Clusters Using Heat or Solvent Vapor

The controlled self‐assembly of CuI and an asymmetric ligand with mixed N/S donors, 2‐(tert‐butylthio)‐N‐(pyridin‐3‐yl)acetamide ( L ), afforded three Cu^I coordination polymers (CPs), [Cu₄I₄ L ₂(MeCN)₂]_n ( 1 ), [Cu₄I₄ L ₂]_n ( 2 ), and {[Cu₄I₄ L ₂] ? MeOH}_n ( 3 ). X‐ray analyses showed that CPs 1 – 3 are supramolecular isomers with 1, 2, and 3D structures, respectively. CP 1 adopts a stairstep Cu₄I₄ cluster, whereas CPs 2 and 3 are composed of cubane‐like Cu₄I₄ clusters. Crystal‐to‐crystal transformations of 1 to 2 and 3 showed reversible transformations between different Cu₄I₄ clusters using heat or solvent (acetonitrile or methanol) vapor. CP 2 was reversibly transformed to 3 by the addition of methanol and heat. Therefore, the transformations between supramolecular isomers 1 , 2 , and 3 are completely reversible.