Bidirectional sex change and plasticity of gonadal phases in the goby Lubricogobius exiguus.

Of the ca. 500 known hermaphroditic fish species, bidirectional sex change and simultaneous hermaphroditism are currently known in 69 and 57 species, respectively. Both bidirectional sex change and simultaneous hermaphroditism are predicted to evolve when mating opportunities are limited, such as in cases of low-density distribution and low mobility of individuals. However, the plasticity of sex is adaptive in obtaining mating opportunities, especially when there is mate loss. Pair-rearing experiments and histological observations of gonads of the goby Lubricogobius exiguus, which has low-density distributions and low mobility, showed bidirectional sex change. The male-role individuals in pairs had gonads in which only the testis was functional (male-phase), whereas the female-role individuals had two types of gonads: only the ovary was functional (female-phase) or both testis and ovary were functional (simultaneously hermaphroditic phase, SH-phase). In addition, single-rearing experiments showed SH-phase gonads in all individuals, and some cyclic spawning but no self-fertilization occurred. These results revealed that L. exiguus has an unusual sexual pattern among hermaphroditic fishes because they undergo bidirectional sex change and some maintain SH-phase gonads. These findings indicate that the low-density distribution and low mobility of L. exiguus in their natural habitat may have influenced the evolution of this unique sexual pattern.

Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor.

We developed and evaluated an anodized-aluminum pressure-sensitive paint (AA-PSP) with new formulations of free-base porphyrin, H2TCPP, as an optical unsteady pressure sensor. The luminophore H2TCPP has quite a short fluorescent lifetime (2.4 ns on the condition of the AA-PSP). The fluorescence spectroscopy result shows that the excitation wavelength of H2TCPP corresponds to violet-colored (425 nm) and green-colored (longer than 520 nm) lights. The pressure sensitivity is sufficiently high for the pressure sensor (0.33-0.51%/kPa) and the temperature sensitivity is very low (0.07-1.46%/K). The photodegradation of the AA-PSPs is not severe in both excitation light sources of the green LED and the Nd:YAG laser. The resonance tube experiment result shows the cut-off frequency of the AA-PSPs is over 9.0 kHz, and the results of the shock tube experiment show the 10 µs order time constant of the normal shock wave.

Markerless Image Alignment Method for Pressure-Sensitive Paint Image.

We propose a markerless image alignment method for pressure-sensitive paint measurement data replacing the time-consuming conventional alignment method in which the black markers are placed on the model and are detected manually. In the proposed method, feature points are detected by a boundary detection method, in which the PSP boundary is detected using the Moore-Neighbor tracing algorithm. The performance of the proposed method is compared with the conventional method based on black markers, the difference of Gaussian (DoG) detector, and the Hessian corner detector. The results by the proposed method and the DoG detector are equivalent to each other. On the other hand, the performances of the image alignment using the black marker and the Hessian corner detector are slightly worse compared with the DoG and the proposed method. The computational cost of the proposed method is half of that of the DoG method. The proposed method is a promising for the image alignment in the PSP application in the viewpoint of the alignment precision and computational cost.

Frequency Response of Pressure-Sensitive Paints under Low-Pressure Conditions.

The characteristics of fast-response pressure-sensitive paints (PSPs) in low-pressure conditions were evaluated. Three representative porous binders were investigated: polymer-ceramic PSP (PC-PSP), anodized-aluminum PSP (AA-PSP), and thin-layer chromatography PSP (TLC-PSP). For each PSP, two types of luminophores, Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP) and tris(bathophenanthroline) ruthenium dichloride (Ru(dpp)3), were used as sensor molecules. Pressure sensitivities, temperature sensitivities, and photodegradation rates were measured and evaluated using a pressure chamber. The effect of ambient pressure on the frequency response was investigated using an acoustic resonance tube. The diffusivity coefficients of PSPs were estimated from the measured frequency response and luminescent lifetime, and the governing factor of the frequency response under low-pressure conditions was identified. The results of static calibration show that PC-PSP/PtTFPP, AA-PSP/Ru(dpp)3, and TLC-PSP/PtTFPP have high pressure sensitivities that exceed 4%/kPa under low-pressure conditions and that temperature sensitivity and photodegradation rates become lower as the ambient pressure decreases. Dynamic calibration results show that the dynamic characteristics of PSPs with PtTFPP are dependent on the ambient pressure, whereas those of PSPs with Ru(dpp)3 are not influenced by the ambient pressure. This observation indicates that the governing factor in the frequency response under low-pressure conditions is the lifetime for PC-PSP and TLC-PSP, whereas the governing factor for AA-PSP is diffusion.

Effect of Oxygen Mole Fraction on Static Properties of Pressure-Sensitive Paint.

The effects of the oxygen mole fraction on the static properties of pressure-sensitive paint (PSP) were investigated. Sample coupon tests using a calibration chamber were conducted for poly(hexafluoroisopropyl methacrylate)-based PSP (PHFIPM-PSP), polymer/ceramic PSP (PC-PSP), and anodized aluminum PSP (AA-PSP). The oxygen mole fraction was set to 0.1-100%, and the ambient pressure (Pref) was set to 0.5-140 kPa. Localized Stern-Volmer coefficient Blocal increased and then decreased with increasing oxygen mole fraction. Although Blocal depends on both ambient pressure and the oxygen mole fraction, its effect can be characterized as a function of the partial pressure of oxygen. For AA-PSP and PHFIPM-PSP, which are low-pressure- and relatively low-pressure-type PSPs, respectively, Blocal peaks at PO2ref<12 kPa. In contrast, for PC-PSP, which is an atmospheric-pressure-type PSP in the investigated range, Blocal does not have a peak. Blocal has a peak at a relatively high partial pressure of oxygen due to the oxygen permeability of the polymer used in the binder. The peak of SPR, which is the emission intensity change with respect to normalized pressure fluctuation, appears at a lower partial pressure of oxygen than that of Blocal. This is because the intensity of PSP becomes quite low at a high partial pressure of oxygen even if Blocal is high. Hence, the optimal oxygen mole fraction depends on the type of PSP and the ambient pressure range of the experiment. This optimal value can be found on the basis of the partial pressure of oxygen.

Characteristic Evaluation of Chameleon Luminophore Dispersed in Polymer.

A temperature-sensitive paint (TSP) using a chameleon luminophore [ Tb 0 . 99 Eu 0 . 01 ( hfa ) 3 ( dpbp ) ] n is proposed. The chameleon luminophore was dispersed in isobutyl methacrylate polymer in a toluene solvent to fix it on a sample coupon. Temperature and pressure sensitivities of the chameleon luminophore-based TSP were measured using a spectrofluorophotometer. The emission for each wavelength was confirmed to be dependent on the temperature and pressure. The temperature and pressure sensitivities of the TSP were 0.81-2.8%/K and 0.08-0.12%/kPa, respectively. Higher temperature sensitivity can be obtained using the ratio of emissions from the two lanthanide ions, Tb III and Eu III . The temperature sensitivity when using the ratio of the emission intensities at 616 nm derived from Eu III and at 545 nm derived from Tb III was 3.2%/K, which was the highest value in the present study. In addition, the pressure sensitivity for the case using the ratio of the emission intensities at 616 and 545 nm was 4 . 8 × 10 - 2 % /kPa. Higher temperature sensitivity and lower pressure sensitivity than that with a single wavelength can be achieved using the ratio of the emission intensities at the two peak wavelengths derived from Tb III and Eu III .

Evaluation of the Characteristics and Coating Film Structure of Polymer/Ceramic Pressure-Sensitive Paint.

Polymer/ceramic pressure-sensitive paint (PC-PSP), which incorporates a high percentage of particles in the binder layer, is proposed in order to improve the characteristics of PSP. The procedure for embedding particles into the binder layer was modified. In the conventional procedure, dye is adsorbed onto a polymer/ceramic coating film (denoted herein as a dye-adsorbed (D-adsorbed) PSP). In the new procedure, the mixture of a dye and particles is adsorbed onto a polymer coating film (denoted herein as the particle/dye-adsorbed (PD-adsorbed) PSP). The effect of particle mass content on PSP characteristics was investigated. In addition, the effect of solvent on PSP characteristics and film structure were evaluated for the PD-adsorbed PSP. As a result, the difference in the PSP characteristics between the two types of PSP was clarified. Although surface roughness and time response increase with increased mass content of particles for both D- and PD-adsorbed PSPs, the critical pigment volume concentration (CPVC) for the PD-adsorbed PSP is smaller than that of the D-adsorbed PSP (88 wt% and 93 wt%, respectively). The PD-adsorbed PSP has a higher frequency response comparing with the D-adsorbed PSP while maintaining the same surface roughness. Observation by scanning electron microscope showed that the CPVC of the PC-PSP is governed primarily by surface structure. The coating film structure can be roughly classified into two states depending on the particle mass content. One is a state in which the coating film consisted of two layers: a lower particle-rich layer and an upper polymer-rich layer. This type of structure was observed in the PD-adsorbed PSP as well as in the D-adsorbed PSP. In the other state, polymer and particles are homogeneously distributed in the film, and pores are formed. This difference in the coating structure results in a change in the time response.