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Abstract: We have investigated the hydrogenation and dehydrogenation properties of binary RNi5 (R: La, Pr, Nd, Sm, Gd, Tb and Dy) intermetallic compounds in the pressure range of 0.1–35 MPa and temperature range of 223–298 K. Pressure–composition isotherms demonstrated that as the atomic number of R increased in RNi5–H systems, the single pressure plateau (LaNi5) split into two plateaux (PrNi5, NdNi5, SmNi5 and GdNi5), and then into three plateaux (TbNi5 and DyNi5), indicating the presence of two hydrides ( and phases) and then three hydrides (, and phases). The and phase transitions in the TbNi5–H system corresponded, respectively, to the and transitions in the RNi5–H (R: Pr, Nd, Sm and Gd) systems having two plateaux. [Copyright &y& Elsevier]

We investigated the pressure–composition (P–C) isotherms of several binary RNi5 (R=La, Ce, Pr, Nd, Sm and Gd) intermetallic compounds to clarify the correlation of the hydrogen storage properties between multi-plateaux. It was found that all RNi5 compounds have similar P–C isotherms with two well-separated plateaux except for CeNi5, indicating that two hydrides with compositions of RNi5H3–4 and RNi5H6–7 are formed. With increasing the atomic number of R element in the RNi5 compounds, the unit cell volume decreases due to the decrease of the radius of the R element. This influences the absolute enthalpies of dehydrogenation |ΔH| of both hydrides (β and γ) to decrease, which consequently leads to the increase of the second plateau pressure as well as the first plateau. Contrary to LaNi5–H2 system, the |ΔH| of γ hydride is smaller than that of |ΔH| of β hydride for the other systems, which indicates that the pressure gap between two plateau pressures expands with decreasing temperature. The second plateau tends to disappear with large atomic number of R element because the |ΔH| value approaches to zero. [Copyright &y& Elsevier]

Abstract: The solution density, viscosity and conductivity of MClO4 (M = Li and Na) solutions in propylene carbonate and γ-butyrolactone are measured at the concentrations of <1.5–2.0 mol dm−3. The partial volume of the solute, derived from the density, of NaClO4 is greater than that of LiClO4 as expected. NaClO4 produces less viscous and more conductive solutions than LiClO4 throughout the examined concentration range. Notably, the conductivity of the NaClO4 solutions is 10–20% higher than that of the LiClO4 solutions at T/K = 298. The validity of the empirical cubic root law, Λ(C) = Λ 0 − AC 1/3, is examined, where Λ and Λ 0 are the molar conductivities at the molarity C and at infinite dilution. The meaning of the slope A is interpreted in the theoretical framework of the pseudolattice model. [Copyright &y& Elsevier]

Abstract: Hf7Ni10 has the same crystal structure as Zr7Ni10, which shows several unusual hydrogenation properties such as reversible hydrogenation by irreversible phase transformation and structural change caused by hydrogenation followed by dehydrogenation, and its hydrogenation properties have been unknown. The phase relation and hydrogenation properties of Hf x Zr7−x Ni10 alloys were investigated in the compositional range from Zr7Ni10 () to Hf7Ni10 (). All the samples were obtained by arc melting followed by heat treatment in vacuum. The constituent phase was identified by the combination of X-ray diffraction and microscopic analysis and hydrogenation properties were examined by differential scanning calorimetry and Sieverts’ method. No structural change from orthorhombic Cmca type to another one such as tetragonal type and orthorhombic Pbca type was observed for the addition of Hf and Hf was substituted for Zr in Zr7Ni10 in all the compositional range we examined. The lattice constant of the aimed phase decreased with an increase in Hf content. The measurements using differential scanning calorimetry indicated that the Hf-substituted alloys showed the same phase transformation as Zr7Ni10 in hydrogenation, that is the unusual phase transformation that an intermediate hydride phase appears only in dehydrogenation but not in hydrogenation. The transformation temperature decreased with an increase in Hf content. [Copyright &y& Elsevier]

The purpose of the present study is to contribute to the establishment of a standard method for evaluating the adverse effects of nanomaterials by intratracheal administration. Low and high doses of multi-walled carbon nanotubes (MWCNTs) were administered to rats in a single administration or the same final dose as the single administration but divided over four administrations. Bronchoalveolar lavage examination on day 14 showed an inflammatory reaction and cytotoxicity in the lung, generally greater at the higher dose, and tending to be greater in the rats with four administrations at both the low and high doses. Histopathologic findings showed increased alveolar macrophages and MWCNT deposition (fibers phagocytosed by alveolar macrophages and fibers that were not phagocytosed) in the alveolar space, granulomatous changes, and MWCNT deposition in bronchus-associated lymphoid tissue (BALT) and lung-related lymph nodes on days 14, 28, and 91. In addition, alveolar type II epithelial hyperplasia was observed on day 91, and fibrosis of the alveolar wall was observed on days 28 and 91. Fewer alveolar macrophages with phagocytosed MWCNTs were present at day 91 compared to day 28. MWCNT deposition tended to be higher in the BALT after a single administration, whereas deposition was higher in the lung-related lymph nodes after four administrations. MWCNTs were considered to be transported from the lungs or BALT to the lymph nodes over time. There were no significant differences in MWCNT deposition in the lung after the single administration compared with four administrations at either the low or high doses, and the histopathological findings were similar after single and four administrations, at both the low and high doses. Based on the above findings, a toxicity evaluation of the nanomaterials can be sufficiently performed by intratracheal administration, even with a single intratracheal administration.

We conducted a two-year inhalation study of butyraldehyde using F344/DuCrlCrlj rats. The rats were exposed to 0, 300, 1,000 and 3,000 ppm (v/v) for 6 hr/day, 5 days/ week for 104 weeks using whole-body inhalation chambers. The incidence of squamous cell carcinoma of the nasal cavity was increased in the 3,000 ppm groups of both male and female rats, with Fisher's exact test and the Peto test indicating that the incidence was significant. In addition to squamous cell carcinoma in the nasal cavity, in the 3,000 ppm groups one male had an adenosquamous carcinoma, one male had a carcinosarcoma, one male had a sarcoma NOS (Not Otherwise Specified), and one female had a squamous cell papilloma in the nasal cavity. The combined incidence of squamous cell carcinoma, adenosquamous carcinoma and carcinosarcoma was significantly increased in male rats and the combined incidence of squamous cell papilloma and carcinoma was significantly increased in female. Based on these results, we conclude that there is clear evidence of butyraldehyde carcinogenicity in male and female rats.

To investigate the carcinogenicity of anatase-type nano-titanium dioxide (aNTiO 2 ), F344/DuCrlCrlj rats were exposed to aNTiO 2 aerosol at concentrations of 0, 0.5, 2, and 8 mg/m 3 . The rats were divided into 2 groups: carcinogenicity study groups were exposed for two years, and satellite study groups were exposed for one year followed by recovery for 1 day, 26 weeks, and 52 weeks after the end of exposure. In the carcinogenicity groups, bronchiolo-alveolar carcinomas were observed in two 8 mg/m 3 -exposed males, showing an increasing trend by Peto's test. However, this incidence was at the upper limit of JBRC's historical control data. Bronchiolo-alveolar adenomas were observed in 1, 2, 3, and 4 rats of the 0, 0.5, 2, and 8 mg/m 3 -exposed females and were not statistically significant. However, the incidence in the 8 mg/m 3 -exposed females exceeded JBRC's historical control data. Therefore, we conclude there is equivocal evidence for the carcinogenicity of aNTiO 2 in rats. No lung tumors were observed in the satellite groups. Particle-induced non-neoplastic lesions (alveolar epithelial hyperplasia and focal fibrosis) were observed in exposed males and females in both the carcinogenicity and satellite groups. Increased lung weight and neutrophils of bronchoalveolar lavage fluid were observed in the 8 mg/m 3 -exposed carcinogenicity groups. The aNTiO 2 deposited in the lungs of the satellite group rats was decreased at 26 weeks after the end of exposure compared to 1 day after the end of exposure. At 52 weeks after the end of exposure, the decreased level was the same at 26 weeks after the end of exposure.

In this review, we focus on the rat pulmonary carcinogenicity of two solid substances, fibrous multi-walled carbon nanotube (MWCNT) and particulate indium tin oxide (ITO). Inhalation exposure to MWNT-7, a type of MWCNTs, and ITO induced lung carcinogenicity in both male and female rats. Toxicity to the alveolar epithelium is induced by macrophages undergoing frustrated phagocytosis or frustrated degradation of engulfed particles (referred to as frustrated macrophages). Melted macrophage contents contribute significantly to development of hyperplasia of the alveolar epithelium, which eventually results in the induction of lung carcinoma. MWNT-7 and ITO induce secondary genotoxicity; consequently, a no-observed-adverse-effect level can be applied to these materials rather than benchmark doses that are used for non-threshold carcinogens. Thus, establishing occupational exposure limit values for MWNT-7 and ITO based on the existence of a carcinogenic threshold is reasonable., Competing Interests: This review paper was written mainly based on the results of contracted carcinogenicity studies (refs. 1 & 2) conducted by the JBRC. The carcinogenicity study of MWCNT was supported by the Ministry of Health, Labour and Welfare of Japan, and that of ITO was supported in collaboration with JX Nippon Mining & Metal, Corp. and the other nine companies. The authors declare no potential conflicts of interest., (©2023 The Japanese Society of Toxicologic Pathology.)