Empirical Abundance Scaling Laws and Implications for the Gamma-Process in Core-Collapse Supernovae

Analyzing the solar system abundances, we have found two empirical abundance scaling laws concerning the p- and s-nuclei with the same atomic number. The first scaling is s/p ratios are almost constant over a wide range of the atomic number, where the p-nculei are lighter than the s-nuclei by two or four neutrons. The second scaling is p/p ratios are almost constant, where the second $p$-nuclei are lighter than the first p-nucleus by two neutrons. These scalings are a piece of evidence that most p-nuclei are dominantly synthesized by the gamma-process in supernova explosions. The scalings lead to a novel concept of "universality of gamma-process" that the s/p and p/p ratios of nuclei produced by individual gamma-processes are almost constant, respectively. We have calculated the ratios by gamma-process based on core-collapse supernova explosion models under various astrophysical conditions and found that the scalings hold for materials produced by individual gamma-processes independent of the astrophysical conditions assumed. The universality originates from three mechanisms: the shifts of the gamma-process layers to keep their peak temperature, the weak s-process in pre-supernovae, and the independence of the s/p ratios of the nuclear reactions. The results further suggest an extended universality that the s/p ratios in the gamma-process layers are not only constant but also centered on a specific value of 3. With this specific value and the first scaling, we estimate that the ratios of $s$-process abundance contributions from the AGB stars to the massive stars are almost 6.7 for the $s$-nuclei of A > 90. We find that large enhancements of s/p ratios for Ce, Er, and W are a piece of evidence that the weak s-process actually occurred before SNe.Comment: 35 pages, 15 figure

Effects of spatially limited external magnetic fields on short sample tests of large-scale superconductors

For short sample tests of large-scale superconductor coil conductors, it is difficult to get sufficient spatial uniformity using external magnetic fields because of the size limitations of test facilities. The effects of spatially limited external magnetic fields on short sample tests are discussed by comparing the test results for narrow and broad external magnetic fields. The authors tested short samples of pool-cooled 10 kA class superconductors using two kinds of split coils which are different in bore size. The measured recovery currents for the narrow external field are more than twice those for the broad field. It shows that the insufficient spatial distribution of the external field biases the stability measurements of superconductor

High levels of oxidatively generated DNA damage 8,5'-cyclo-2'-deoxyadenosine accumulate in the brain tissues of xeroderma pigmentosum group A gene-knockout mice.

Xeroderma pigmentosum (XP) is a genetic disorder associated with defects in nucleotide excision repair, a pathway that eliminates a wide variety of helix-distorting DNA lesions, including ultraviolet-induced pyrimidine dimers. In addition to skin diseases in sun-exposed areas, approximately 25% of XP patients develop progressive neurological disease, which has been hypothesized to be associated with the accumulation of an oxidatively generated type of DNA damage called purine 8,5'-cyclo-2'-deoxynucleoside (cyclopurine). However, that hypothesis has not been verified. In this study, we tested that hypothesis by using the XP group A gene-knockout (Xpa-/-) mouse model. To quantify cyclopurine lesions in this model, we previously established an enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody (CdA-1) that specifically recognizes 8,5'-cyclo-2'-deoxyadenosine (cyclo-dA). By optimizing conditions, we increased the ELISA sensitivity to a detection limit of ˜one cyclo-dA lesion/106 nucleosides. The improved ELISA revealed that cyclo-dA lesions accumulate with age in the brain tissues of Xpa-/- and of wild-type (wt) mice, but there were significantly more cyclo-dA lesions in Xpa-/- mice than in wt mice at 6, 24 and 29 months of age. These findings are consistent with the long-standing hypothesis that the age-dependent accumulation of endogenous cyclopurine lesions in the brain may be critical for XP neurological abnormalities

The Wnt Antagonist Frzb-1 Regulates Chondrocyte Maturation and Long Bone Development during Limb Skeletogenesis

AbstractThe Wnt antagonist Frzb-1 is expressed during limb skeletogenesis, but its roles in this complex multistep process are not fully understood. To address this issue, we determined Frzb-1 gene expression patterns during chick long bone development and carried out gain- and loss-of-function studies by misexpression of Frzb-1, Wnt-8 (a known Frzb-1 target), or different forms of the intracellular Wnt mediator LEF-1 in developing limbs and cultured chondrocytes. Frzb-1 expression was quite strong in mesenchymal prechondrogenic condensations and then characterized epiphyseal articular chondrocytes and prehypertrophic chondrocytes in growth plates. Virally driven Frzb-1 misexpression caused shortening of skeletal elements, joint fusion, and delayed chondrocyte maturation, with consequent inhibition of matrix mineralization, metalloprotease expression, and marrow/bone formation. In good agreement, misexpression of Frzb-1 or a dominant-negative form of LEF-1 in cultured chondrocytes maintained the cells at an immature stage. Instead, misexpression of Wnt-8 or a constitutively active LEF-1 strongly promoted chondrocyte maturation, hypertrophy, and calcification. Immunostaining revealed that the distribution of endogenous Wnt mediator β-catenin changes dramatically in vivo and in vitro, from largely cytoplasmic in immature proliferating and prehypertrophic chondrocytes to nuclear in hypertrophic mineralizing chondrocytes. Misexpression of Frzb-1 prevented β-catenin nuclear relocalization in chondrocytes in vivo or in vitro. The data demonstrate that Frzb-1 exerts a strong influence on limb skeletogenesis and is a powerful and direct modulator of chondrocyte maturation, phenotype, and function. Phases of skeletogenesis, such as terminal chondrocyte maturation and joint formation, appear to be particularly dependent on Wnt signaling and thus very sensitive to Frzb-1 antagonistic action