4 research outputs found
The Origin of Carbon-Enhancement and Initial Mass Function of Extremely Metal-Poor Stars in the Galactic Halo
It is known that the carbon-enhanced, extremely metal-poor (CEMP) stars
constitute a substantial proportion in the extremely metal-poor (EMP) stars of
the Galactic Halo, by far larger than CH stars in Population II stars. We
investigate their origin with taking into account an additional evolutionary
path to the surface carbon-enrichment, triggered by hydrogen engulfment by the
helium flash convection, in EMP stars of . This process
is distinct from the third dredge-up operating in more metal-rich stars and
also in EMP stars. In binary systems of EMP stars, the secondary stars become
CEMP stars through mass transfer from the primary stars of low and intermediate
masses, which have developed the surface carbon-enhancement. Our binary
scenario can predict the variations in the abundances not only for carbon but
also for nitrogen and s-process elements and reasonably explain the observed
properties such as the stellar distributions with respect to the carbon
abundances, the binary periods, and the evolutionary stages. Furthermore, from
the observed frequencies of CEMP stars with and without s-process element
enhancement, we demonstrate that the initial mass function of EMP stars need to
give the mean mass ~10\msun under the reasonable assumptions on the
distributions of orbital separations and mass ratio of binary components. This
also indicates that the currently observed EMP stars were exclusively born as
the secondary members of binaries, making up remnants of EMP binary
systems of mass ~10^8\msun in total; in addition to CEMP stars with white
dwarf companions, a significant fraction of them have experienced supernova
explosions of their companions. We discuss the implications of the present
results in relation to the formation of Galactic halo.Comment: 66 pages, 12 figures, 2 tables Accepted for publication in Ap
Current status of tertiary debulking surgery and prognosis after secondary debulking surgery for recurrent Müllerian epithelial cancer in Japan: a retrospective analysis of 164 patients (KCOG-G1402)
BackgroundThis study aimed to evaluate the current status of secondary debulking surgery (SDS) and tertiary debulking surgery (TDS; performed for recurrence after SDS) and to assess the overall survival after recurrence of Müllerian epithelial cancer in Japan. We also evaluated the data of patients who underwent a fourth debulking surgery (i.e., quaternary debulking surgery (QDS)).MethodsWe conducted a retrospective study of 164 patients with recurrent Müllerian epithelial cancers (i.e., ovarian, tubal, and peritoneal cancers). The SDS was performed between January 2000 and September 2014 in 20 Japanese hospitals. Clinicopathological data were collected and analyzed.ResultsOf the 164 patients, 66 patients did not have a recurrence or died after SDS. Ninety-eight patients had a recurrence after SDS. Forty-three of the 98 patients underwent TDS; 55 of the 98 patients did not undergo TDS and were classified into the non-TDS group. The overall survival (OS) after SDS was significantly better in the TDS group than in the non-TDS group. The median OS after SDS was 123 and 42 months in the TDS group and non-TDS group, respectively. Of the 43 patients who received TDS, 11 patients were further treated with QDS. The median OS after SDS was 123 months for patients who underwent QDS.ConclusionsThis multicenter study on the prognosis of post-SDS is apparently the first report on QDS in Japan. Patients undergoing TDS have a good prognosis, compared to patients in the non-TDS group. Novel drugs are being evaluated; however, debulking surgery remains a necessary treatment for recurrence