The Virgo High-Resolution CO Survey. II. Rotation Curves and Dynamical Mass Distributions

Based on a high-resolution CO survey of Virgo spirals with the Nobeyama Millimeter-wave Array, we determined the dynamical centers using velocity fields, and derived position-velocity diagrams (PVDs) along the major axes of the galaxies across their dynamical centers. We applied a new iteration method to derive rotation curves (RCs), which reproduce the observed PVDs. The obtained high-accuracy RCs generally show steep rise in the central 100 to 200 pc regions, followed by flat rotation in the disk. We applied a deconvolution method to calculate the surface-mass density (SMD) using the RCs based on two extreme assumptions that the mass distribution is either spherical or thin-disk shaped. Both assumptions give nearly identical results, agreeing with each other within a factor of two at any radii. The SMD distributions revealed central massive cores with peak SMD of 10^4 - 10^5 Msun pc^-2 and total mass within 200 pc radius of the order of about 10^9 Msun Correlation analysis among the derived parameters show that the central CO-line intensity is positively correlated with the central SMD, which suggests that the deeper is the gravitational potential, the higher is the molecular gas concentration in the nuclei regardless morphological types.Comment: PASJ 2003 in press, Latex 12 pages, 6 figures (Bigger gif/ps figures available at http://www.ioa.s.u-tokyo.ac.jp/radio/virgo2

Resonant Two-Magnon Raman Scattering and Photoexcited States in Two-Dimensional Mott Insulators

We investigate the resonant two-magnon Raman scattering in two-dimensional (2D) Mott insulators by using a half-filled 2D Hubbard model in the strong coupling limit. By performing numerical diagonalization calculations for small clusters, we find that the Raman intensity is enhanced when the incoming photon energy is not near the optical absorption edge but well above it, being consistent with experimental data. The absence of resonance near the gap edge is associated with the presence of background spins, while photoexcited states for resonance are found to be characterized by the charge degree of freedom. The resonance mechanism is different from those proposed previously.Comment: REVTeX4, 4 pages, 3 figures, to be published in Phys. Rev. Let

Effect of Gravity on the Macro-Segregation of Larger Steel Ingots

Upon the problem involved in the study of solidification and segregation of larger steel ingots numerous papers have hitherto been published. Nevertheless their nature is still vague from both the scientific and practical points of view. Previous studies have been devoted to the measurement of specific physical values of molten steel, the detailed observation of the sections of solidified ingots, simulat-ion experiments using different materials, experiments on the formation and change of non-metallic inclusions, etc. Isn't there any room for re-examination in these methods of study? Even if these items could be clarified in details, it would not give rise to a satisfactory solut-ion for the phenomenon of ''differential freezing" and to the reduction of segregation and other accompanied defects. We feel much necessity of thorough studies on the solidi-fication and segregation of large steel ingots, before we rush into the epoch of large scale vacuum casting of steel ingots

Transformation Characteristics of Large Steel Forgings

Inspite of voluminous papers hitherto published on the heat treatment of large steel forgings,it would not he exaggerated to say that the transformation characteri-stics of them are not fully known yet. The cause is attributed , to our best knowledge, to those factors as inner local properties of original ingots , effects of forging and accompanied soaking, liberation and trans-mission of latent heat of transformation , Hydrogen retained at the deep portions, thermal and transformat- ion stresses etc. which refuse analogy with the results obtained by means of small specimens

A Contribution to the Service Failure of Large Chilled Iron Rolls due to Fatigue

A case of service rupture of chilled iron roll due to fatigue is presented with condition of rupture, invest-igation of the cause, and remedial result through remo-delling. As a result of this, it is suggested that service strength of chilled iron rolls should be considered through fatigue, and that standard size is not necessar-ily of sufficient strength from this point of view ; a remark for the prevention of service failures in existent mills, and to which reference is desired to make in bui-lding new mill

Temperature and Dimensionality Dependences of Optical Absorption Spectra in Mott Insulators

We investigate the temperature dependence of optical absorption spectra of one-dimensional (1D) and two-dimensional (2D) Mott insulators by using an effective model in the strong-coupling limit of a half-filed Hubbard model. In the numerically exact diagonalization calculations on finite-size clusters, we find that in 1D the energy position of the absorption edge is almost independent of temperature, while in 2D the edge position shifts to lower energy with increasing temperature. The different temperature dependence between 1D and 2D is attributed to the difference of the coupling of the charge and spin degrees of freedom. The implications of the results on experiments are discussed in terms of the dimensionality dependence.Comment: 5 pages, 4 figure

Theoretical study of angle-resolved two-photon photoemission in two-dimensional insulating cuprates

We propose angle-resolved two-photon photoemission spectroscopy (AR-2PPES) as a technique to detect the location of the bottom of the upper Hubbard band (UHB) in two-dimensional insulating cuprates. The AR-2PPES spectra are numerically calculated for small Hubbard clusters. When the pump photon excites an electron from the lower Hubbard band, the bottom of the UHB is less clear, but when an electron in the nonbonding oxygen band is excited, the bottom of the UHB can be identified clearly, accompanied with additional spectra originated from the spin-wave excitation at half filling.Comment: 5 pages, 4 figure

Investigation of the thermal expansion and heat capacity of the CaCu3Ti4O12 ceramics

The thermal expansion of the CaCu3Ti4O12 ceramics has been measured over a wide temperature range 120–1200 K. The high quality of the samples under study has been confirmed by good agreement of the results of measurements of the heat capacity in the range 2–300 K and in the vicinity of the phase transition of magnetic nature at 25 K with the data for the single crystal. No anomalies in the thermal expansion that can be associated with the phase transition at 726–732 K assumed by other investigators have been found. The influence exerted on the thermal expansion by the heat treatment of the sample in a helium atmosphere and in air has been investigated