Heat capacity of liquid transition metals obtained with aerodynamic levitation

The development of contactless measurement methods has allowed investigating the properties of molten materials at high temperatures in a controlled environment. As the sample is not in contact with any container walls while being heated, levitation techniques have an edge over traditional contact methods at elevated temperatures. Among the various thermophysical properties of interest, it has been challenging to measure heat capacity with levitation techniques because it is directly related to the emissivity of the sample. Previous studies on heat capacity measurement with various levitation techniques have produced results with large deviations, especially at elevated temperatures. In addition, there is a general lack of information on the heat capacity of liquid transition metals at temperatures exceeding 2000 K, especially using conventional calorimetry methods. In this study, we successfully obtained the isobaric heat capacity of liquid transition metals such as Co, Hf, Ir, Mo, Nb, Rh, Ru, Ti, V, and Zr with aerodynamic levitation using the newly developed “multiple-gas cooling” method. A comparison between our reported values and reference data enabled us to assess the accuracy of previous experiments and provide much needed heat capacity data for high-temperature liquid metals. This study highlights the applicability and reliability of the multiple-gas cooling method for measuring the heat capacity of liquid non-noble metals at temperatures approaching 3000 K

Efficacy, tolerability and safety of once-monthly administration of 75mg risedronate in Japanese patients with involutional osteoporosis: A comparison with a 2.5mg once-daily dosage regimen

AbstractOral risedronate has been shown to be effective in the treatment of osteoporosis when administered once-daily or once-weekly in Japan. This randomized, double-blind, multicenter 12-month study was conducted to compare the efficacy and tolerability of oral risedronate 75mg once-monthly with 2.5mg once-daily in Japanese patients with involutional osteoporosis. Bone mineral density (BMD), biochemical markers of bone metabolism, fractures, and adverse events (AEs) were evaluated. At the end of the study (Month 12, last observation carried forward [M12, LOCF]), mean percent change (SD) from baseline in lumbar spine (L2–L4) BMD, measured by dual energy X-ray absorptiometry (primary endpoint), was increased by 5.69 (4.00)% in the 2.5mg once-daily group (n=428), and 5.98 (4.54)% in the 75mg once-monthly group (n=422). In the non-inferiority t-test (non-inferiority margin Δ=1.5%), the 75mg once-monthly group was non-inferior to the 2.5mg once-daily group (p<0.0001). The difference between treatment groups was 0.28% (95% CI, −0.31% to 0.88%). Changes in biochemical markers of bone metabolism were generally comparable in the two groups, although decreases in the percent change from baseline in urinary NTX/CRN and CTX/CRN were statistically greater in the 2.5mg once-daily group than the 75mg once-monthly group. The frequency of new vertebral fractures (including aggravation of prevalent fractures) at the end of the study (M12, LOCF) was also similar in the two groups: 1.2% in the 2.5mg once-daily group and 1.3% in the 75mg once-monthly group.The incidence of mild/moderate/severe AEs was 75.5%/6.3%/0.5% in the 2.5mg once-daily group and 77.7%/8.1%/0.7% in the 75mg once-monthly group. AEs associated with gastrointestinal symptoms occurred in approximately 30% of subjects in each group but with no severe cases. AEs potentially associated with acute phase reaction (including symptoms of influenza-like illness or pyrexia starting within 3days of the first dose of the study drug and with a duration of 7days or less) only occurred in the 75mg once-monthly group (2.1%, 9/422 subjects; influenza-like symptoms in 1 subject and pyrexia in 8 subjects), although the incidence was low without any severe cases.In conclusion, risedronate 75mg once-monthly (a dosage which is 30 times higher than risedronate 2.5mg once-daily) had non-inferior efficacy in terms of BMD and was similarly well tolerated compared to the once-daily regimen in Japanese patients with involutional osteoporosis. Consistent with the once-daily and once-weekly dosage, the once-monthly dosage of risedronate 75mg was half that used outside Japan (150mg)

Phase behavior of oxidized Ce and Gd-doped (U,Zr)O₂

Re-criticality analysis of the fuel debris at the Fukushima Dai-ichi Nuclear Power Plant is the key step to ensure the safe retrieval and storage of the fuel debris. Knowledge of the amount and distribution of Pu and Gd within the fuel debris greatly contributes to such analysis as they directly affect the fission-chain reaction. However, little is known about how Pu-doped and Gd-doped (U, Zr)O₂ solid solutions oxidize and whether phases concentrated in Pu or Gd form. In this study, CeO₂ is used as a surrogate material for PuO₂ because of the similarities in their crystal structures and valence states. (U₀.₉-xZr₀.₁Cex)O₂ and (U₀.₉-xZr₀.₁Gdx)O₂ solid solutions are prepared by sintering under an argon atmosphere and oxidized at 1073 K in air for 2 hours to simulate heavily oxidized fuel debris. Samples doped with 5 at% Ce and Gd contain only an orthorhombic-U3O8-x phase after oxidation, but its diffraction peaks’ intensities decrease as the amount of dopant increases. The phase transformation of (U₀.₉-xZr₀.₁Gdx)O₂, with further oxidation, is found to be cubic-(U, Zr, Gd)O₂+x → orthorhombic-(U, Zr, Gd)₃O₇±x → orthorhombic-(U, Zr, Gd)₃O₈-x. SEM/EDS analysis reveals that Ce and Gd are uniformly distributed in the (U₀.₉-xZr₀.₁REx)O₂ (RE = Ce, Gd) samples after oxidation

Chalcopyrite ZnSnSb_2: A Promising Thermoelectric Material

Ternary compounds with a tetragonal chalcopyrite structure, such as CuGaTe2, are promising thermoelectric (TE) materials. It has been demonstrated in various chalcopyrite systems, including compounds with quaternary chalcopyrite-like structures, that the lattice parameter ratio, c/a, being exactly 2.00 to have a pseudo-cubic structure is key to increase the degeneracy at the valence band edge and ultimately achieve high TE performance. Considering the fact that ZnSnSb_2 with a chalcopyrite structure is reported to have c/a close to 2.00, it is expected to have multiple valence bands leading to a high p-type zT. However, there are no complete investigations on the high temperature TE properties of ZnSnSb_2 mainly because of the difficulty of obtaining a single-phase ZnSnSb_2. In the present study, pure ZnSnSb_2 samples with no impurities are synthesized successfully using a Sn flux-based method and TE properties are characterized up to 585 K. Transport properties and thermal analysis indicate that the structure of ZnSnSb_2 remains chalcopyrite with no order–disorder transition and clearly show that ZnSnSb_2 can be made to exhibit a high zT in the low-to-mid temperature range through further optimization

Enhancement of thermoelectric properties of p-type single-filled skutterudites CexFeyCo4-ySb12 by tuning the Ce and Fe content

CoSb3-based filled skutterudites are known as good n-type thermoelectric (TE) materials. However, the p-type ones have not been intensively investigated. In this study, we focus on Ce-filled Fe-substituted CoSb3 as p-type skutterudites, where Fe will act as a hole dopant. Polycrystalline samples with nominal compositions of CexFeyCo4-ySb12 (x = 0.8, 0.9, 1.0 and y = 3.0, 3.5) are synthesized and the high temperature TE properties are investigated. All the samples show the p-type conduction as we expected. It is found that the samples with y = 3.5 exhibit clearly lower κlat values than those of the samples with y = 3.0, meaning that the Fe/Co substitution is more predominant than the Ce filling for the κlat reduction. The maximum zT value observed in this study is 0.78 at 704 K for the sample with x = 1.0, y = 3.5, which is close to the best value reported so far for Ce-filled Fe-substituted CoSb3-based p-type skutterudites

A curl antenna

A radiation element, designated as a curl antenna, is proposed for a circularly polarized antenna. The radiation characteristics of the curl are numerically analyzed. The gain is approximately 8.4 dB, and the 3-dB axial ratio criterion is 6.7%. Two aspects of curl array antennas are also presented: a decoupling factor between two curls and a circular array antenna consisting of 168 curls. Calculations show how the decoupling factor depends on the relative rotation angle of the two curls. The 168-curl array antenna shows a high aperture efficiency of 95%

Thermophysical and mechanical properties of LaB₆ and CeB₆ synthesized through spark plasma sintering

Following the Fukushima Daiichi nuclear power plant accident in 2011, the development of accident tolerant fuels (ATFs) has become an integral part of the promotion of nuclear safety. Of the many design criteria, a high thermal conductivity reduces a fuel pellet's peak temperature and radial temperature gradient. Although various uranium borides such as UB₂ and UB₄ are promising ATFs that have high-temperature stability, high uranium density, and good thermal conductivity, little is known about UB₆, as it has yet to be fabricated under normal conditions. As a metal hexaboride, UB₆ may have excellent electrical conductivity, likely giving it a much higher thermal conductivity than that of UO₂. In this work, we investigate the thermophysical and mechanical properties of non-radioactive LaB₆ and CeB₆ to estimate the potential properties of UB₆, as it has yet to be successfully fabricated. The thermophysical properties of UB₆ are compared with those of UO₂, UB₂, and UB₄ to help clarify whether future attempts at fabricating UB₆ under high pressure or with other dopants are worthwhile for the development of ATFs