Highlights･ Gsdf is expressed predominantly in XY gonads in the Nile tilapia.･ Gsdf expression pattern shows sexual dimorphism before morphological differentiation.･ Gsdf expression is the earliest gene expression detected in testis differentiation.･ Overexpression of gsdf is sufficient to induce testis differentiation in XX tilapia.Abbreviations: transforming growth factor-beta (TGF-beta), gonadal soma-derived factor (gsdf), doublesex/mab-3-related transcription factor-1 (Dmrt1), days post-hatching (dph), quantitative one-step RT-PCR (qRT-PCR), in situ hybridization (ISH) 2 ABSTRACTThe Nile tilapia, Oreochromis niloticus, is a gonochoristic teleost fish with an XX/XY genetic system and is an excellent model for gonadal sex differentiation. In the present study, we screened novel genes that were expressed predominantly in either XY or XX undifferentiated gonads during the critical period for differentiation of gonads into ovaries or testes using 5 microarray screening. We focused on one of the isolated 12 candidate genes, #9475, which was an ortholog of gsdf (gonadal soma-derived factor), a member of the transforming growth factor-beta superfamily. #9475/gsdf showed sexual dimorphism in expression in XY gonads before any other testis differentiation-related genes identified in this species thus far. We also overexpressed the #9475/gsdf gene in XX tilapia, and XX tilapia bearing the #9475/gsdf gene 10 showed normal testis development, which suggests that #9475/gsdf plays an important role in male determination and/or differentiation in tilapia.

We have investigated the ball milling effects for thermoelectric Bi1− x Sr x CuSeO materials. The characteristic rotation speed R for the ball milling exists, at which the crystallite size of the starting powder suddenly decreased. The grain size in the bulks sintered using ball-milled powders also decreased and thermoelectric properties were enhanced mainly by the induced carriers, rather than by the reduction in thermal conductivity. The ball milling effects of carrier doping on thermoelectricity are discussed.

We compared the INNOVA2000 (INNOVA), which has a flat panel detector system, and the Advantx LCLP (LCLP), which has a conventional I. I. system, in terms of the dependence of phantom thickness on patient surface dose (surface dose) and receptor entrance dose (entrance dose). We examined the reduction in surface dose and entrance dose by using an additional filter and shortening the patient detector distance (PDD). The surface dose rate for fluoroscopy with INNOVA was 73.8-63.5%, and the reduction rate was high at a phantom thickness of less than 20 cm compared with LCLP, but such a reduction could not be expected at a phantom thickness of more than 30 cm, depending on maximum dose rate. The rate of reduction in surface dose in the case of exposure was considerably low at a phantom thickness of about 20 cm, while the other's (5, 10, 15, 25, 30 cm) reduction rates were about 40%. The length of PDD with INNOVA was shortened by 5 cm compared with LCLP. As a result, we obtained a reduction rate of surface dose of 11-15%, while the entrance dose was 10% lower. The reduction rate achieved with an additional filter was 43-60% in surface dose rate in fluoroscopy, whereas that of surface dose for exposure was about 50% at phantom thicknesses up to 20 cm, but remained just 25% thereafter. The results indicated that the reduction of surface dose with INNOVA could be changed by means of the phantom thickness, and we consider the effect achieved by the addition of a filter to be the main factor.

Li y CoO2 has a similar layered structure to Na y CoO2, which is a typical p-type oxide thermoelectric material, and the average Co valence of 3 + y is controlled by the Li content y. We investigated the thermoelectric properties of LiCo1− x M x O2 samples (M = Cu, Mg, Ni, Zn) for the first time at high temperatures, in which Co3+ was substituted by the divalent M2+ ions, and the average Co valence of 3 + x can be controlled similarly to the Li content y in Li y CoO2. The substitution of the M2+ ions for the Co site was found to show thermoelectric properties similar to those of Li y CoO2 with the same average Co valence. The Mg-doped sample showed the highest thermoelectric performance at high temperatures in this study; the thermoelectric power factor P is 2.38 × 10−4 W m−1 K−2 at 1173 K and the dimensionless figure of merit ZT is 0.024 at 876 K. The thermoelectric potential of LiCo1− x M x O2 is discussed and compared with those of Li y CoO2 and Na y CO2 systems.

To increase the output power of polymer electrolyte fuel cells (PEFCs), it is important to reduce the oxygen transport resistance in the cathode catalyst layer (CL). The authors have been conducted detailed analysis of the oxygen transport resistance elements: the diffusion resistances in the CL pores, the dissolution resistance into the ionomer, and the transport resistance at the Pt surface. This study improved the method of fabrication of CL and measurement of limiting current for reliable evaluation of oxygen transport resistance in the CL. Using the experimental results, the oxygen transport resistance elements were evaluated, and the transport resistance at Pt surface was confirmed to be dominant even in the improved methods. However, the difference between the model analysis and experimental values became large at CLs with low Pt loadings. To elucidate appropriate structures of the low Pt CLs with smaller oxygen transport resistance, further detailed study is needed.