The ⌳ 13 C hypernucleus was studied by measuring ␥ rays in coincidence with the 13 C(K Ϫ , Ϫ ) reaction. ␥ rays from the 1/2 Ϫ and 3/2 Ϫ states, which are the partners of the spin-orbit doublet states with a predominant configuration of ͓ 12 C g.s. (0 ϩ ) p ⌳ ͔, to the ground state were measured. The splitting of the states was found to be ⌬E(1/2 Ϫ Ϫ3/2 Ϫ )ϭϩ152Ϯ54(stat)Ϯ36(syst) keV. This value is 20-30 times smaller than that of single particle states in nuclei around this mass region. The j ⌳ ϭl ⌳ Ϫ1/2͓(p 1/2 ) ⌳ ͔ state appeared higher in energy, as in normal nuclei. The value gives new insight into the Y N interaction. The excitation energies of the 1/2 Ϫ and 3/2 Ϫ states were obtained as 10.982Ϯ0.031(stat)Ϯ0.056(syst) and 10.830Ϯ0.031(stat)Ϯ0.056(syst) MeV, respectively. We also observed ␥ rays from the 3/2 ϩ state, which has a ͓ 12 C(2 ϩ ) s ⌳ ͔ configuration, to the ground state in ⌳ 13 C. The excitation energy of the 3/2 ϩ state was obtained as 4.880Ϯ0.010(stat) Ϯ0.017(syst) MeV. Nuclear ␥ rays with energies of 4.438 and 15.100 MeV had similar yields, which suggests that a quasifree knockout of a ⌳ particle is dominant in highly excited regions.

The spin-orbit splitting of Lambda single-particle states in (13)(Lambda)C was measured. The 13C(K-,pi(-))(13)(Lambda)C reaction was used to excite both the 1/2(-) and 3/2(-) states simultaneously, which have predominantly 12C(0(+)) x p(Lambda) configuration. gamma rays from the states to the ground state were measured in coincidence with the pi(-)'s, by which ls splitting was found to be 152+/-54(stat)+/-36(syst) keV. The value is 20-30 times smaller than exhibited by the ls splitting in the nuclear shell model. This value gives us new insight into the YN interaction.

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SynopsisCenter segregation is one of the most harmful defects especially for the production of high carbon steel by the continuous casting process.Many experiments were performed to improve center segregation through laboratory tests and plant trials. In the plant trials of bloom c.c. and billet c.c., two or three stirrers were installed at a mold, the upper and lower parts of the secondary cooling zone.As a result, it was found that both the deviation and the mean value of center segregation were gteatly reduced by combination stirring at the mold and in the lower part of the secondary cooling zone. Furthermore, there was an optimum condition for the stirring at a later stage of solidification and center segregation showed no change or even became worse if the stirring condition was not satisfactory.Combination stirring was adopted to the bloom caster and as a result, high quality steels for rods and bars are being produced.

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