A Flexible and Robust Structural Color Film Obtained by Assembly of Surface-Modified Melanin Particles.

In this study, core-shell-hairy-type melanin particles surface modified with a polydopamine shell layer and a polymer brush hairy layer were fabricated and assembled to readily obtain bright structural color films. The hot pressing of freeze-dried samples of melanin particles decorated with a hydrophilic, low glass transition temperature polymer brush results in films that exhibit an angle-dependent structural color due to a highly periodic microstructure, with increased regularity in the arrangement of the particle array due to the fluidity of the particles. Flexible, self-supporting, and easy-to-cut and process structural color films are obtained, and their flexibility and robustness are demonstrated using compression tests. This method of obtaining highly visible structural color films using melanin particles as a single component will have a significant impact on practical materials and applications.

Mechanical Clinching and Self-Pierce Riveting of Thin Three Sheets of 5000 Series Aluminium Alloy and 980 MPa Grade Cold Rolled Ultra-High Strength Steel.

One thin 5000 series aluminium alloy sheet and two thin 980 MPa grade cold rolled ultra-high strength steel sheets were joined by self-pierce riveting and mechanical clinching processes. The joinabilities for a combination of the aluminium and steel sheets in both processes were investigated for different die shapes in the experiment and finite element simulation. In self-pierce riveting, the three sheets were successfully joined for both combinations of the upper and lower aluminium alloy sheets by optimizing the shapes of a die and rivet. In mechanical clinching, the three sheets were successfully joined by an optimum die for the configuration of the upper aluminium alloy sheet. On the other hand, the three sheets for the configuration of the lower aluminium alloy sheet were not joined even by optimizing the die shape in the both finite element simulation and experiment, because the material flow of the steel sheets was insufficient to form the two interlocks. The tension-shear loads for the clinched and riveted sheets with the adhesive were almost the same, because the load for the adhesive was the highest. In the cross-tension test, however, the load by the adhesive was comparatively small.

Multiple Looks of Auditory Empty Durations Both Improve and Impair Temporal Sensitivity.

Discrimination of two neighboring empty durations that are marked by three successive sounds is improved when the presentation of the first (standard, S) duration is repeated before that of the second (comparison, C), as SSSSC. This improvement in sensitivity, called the multiple-look effect, has been explained by a statistical model regarding variability. This model assumes that the perceived duration of the standard is averaged across observations (within a trial within an individual). The increasing of the number of observations thus reduces the standard error of the mean perceived duration. Alternatively, the multiple-look effect is attributed to the listener's prediction based on regular rhythm. Listeners perceive regular rhythm during the repetition of the standard, predict the timing of subsequent sounds, and detect a sound that is displaced from the predicted timing. These models were tested in the present experiment in which the main factor was a temporal separation between the standard and the comparison; i.e., these durations were adjacent to each other as SSSSC or separated by a temporal blank as SSSS_C. The results differed between stimulus structures. First, the multiple-look effect was replicated in the SSSSC condition (yielding a higher performance than SC), but disappeared in SSSS_C (having no difference with S_C). Second, no multiple-look effect occurred in CSSSS (no difference with CS), and moreover, an impairment effect was observed in C_SSSS (a lower performance than C_S). Finally, discrimination was improved in SSSS_CCCC compared with SSSSCCCC, the effect being kept even when sounds were aligned at irregular intervals. These findings are not consistent with those expected from the statistical model because the temporal separation should have produced no effects if the number of standards had been a sole parameter determining the multiple-look effect. The prediction-based model can explain the first finding; inserting a blank between the standard and the comparison violates the listener's prediction based on regular rhythm, thus reducing the multiple-look effect. However, it did not expect the other findings and required revisions. Notably, the second finding indicates that the formation of regular rhythm can impair temporal discrimination. In other words, an inversed multiple-look effect occurs.

Evaluation of colors in green mutants isolated from purple bacteria as a host for colorimetric whole-cell biosensors.

The change in carotenoid-based bacterial color from yellow to red can be applied to whole-cell biosensors. We generated several green mutants to emphasize the color change in such biosensors. The blue-green crtI-deleted mutant, Rhodopseudomonas palustris no.711, accumulated the colorless carotenoid precursor, phytoene. Green Rhodovulum sulfidophilum M31 accumulated neurosporene, a downstream product of phytoene. Another green mutant, Rhodobacter sphaeroides Ga, accumulated neurosporene and chloroxanthin, which are both downstream products of phytoene. All green mutants accumulated bacteriochlorophyll a. Photosynthetic membrane obtained from the green mutants all exhibited decreased absorption of wavelength range at 510-570 nm. Therefore, these indicate that the greenish bacterial colors were mainly caused by the existence of bacteriochlorophyll a and the changes in carotenoid composition in photosynthetic membrane. The colors of the green mutants and their wild-type strains were plotted in the CIE-L*a*b* color space, and the color difference (DeltaE*ab) values between a green mutant and its wild type were calculated. DeltaE*ab values were higher in the green mutants than in Rdv. sulfidophilum CDM2, the yellowish host strain of reported biosensors. These data indicate that change in bacterial color from green to red is more distinguishable than that from yellow to red as a reporter signal of carotenoid-based whole-cell biosensors.

Colorimetric dimethyl sulfide sensor using Rhodovulum sulfidophilum cells based on intrinsic pigment conversion by CrtA.

A colorimetric whole-cell sensor for dimethyl sulfide (DMS) was constructed based on the in vivo conversion of intrinsic pigments in response to the analyte. In a marine bacterium, Rhodovulum sulfidophilum, carotenoids are synthesized via the spheroidene pathway. In this pathway, demethylspheroidene, a yellow carotenoid, is converted to spheroidene under catalysis of O-methyltransferase. Spheroidene monooxygenase (CrtA) catalyzes the terminal step of the pathway and converts spheroidene to spheroidenone, a red carotenoid. Here, the CrtA gene in R. sulfidophilum was removed and then reintroduced downstream of the DMS dehydrogenase gene promoter. Using this whole-cell sensor, 3 muM DMS or dimethyl sulfoxide can be detected without adding any color-forming reagent. The ratio of the red spheroidenone to total carotenoids increased, as the DMS concentration was raised to 0.3 mM. Comparison of the signal to the background color indicated a shift in the color coordinate from a yellow to a red hue. An intense signal was obtained with 1-day incubation at a high cell density when sensor cells at the exponential growth phase were used. These results show that the genetically engineered R. sulfidophilum cells can be used to monitor the quality of marine aquacultural environments by the naked eye.

Unusual accumulation of demethylspheroidene in anaerobic-phototrophic growth of crtA-deleted mutants of Rhodovulum sulfidophilum.

Rhodovulum sulfidophilum produces carotenoids in the spheroidene pathway. Spheroidene monooxygenase, CrtA, catalyzes the conversion of spheroidene to spheroidenone. crtA-deleted mutants of R. sulfidophilum did not produce spheroidenone and demethylspheroidenone. In these mutants, the ratio of demethylspheroidene to spheroidene increased with exposure to light. One mutant exhibiting a spheroidene-predominant phenotype did not grow under anaerobic-light conditions and was devoid of bacteriochlorophyll a, even under semiaerobic-light conditions There was no difference in the growth of the mutants under aerobic-dark conditions. These data suggest that demethylspheroidene is important for photosynthesis in R. sulfidophilum.