Finite Temperature Effects in One-dimensional Mott-Hubbard Insulator: Angle-Resolved Photoemission Study of Na_{0.96}V_{2}O_{5}

We have made an angle-resolved photoemission study of a one-dimensional (1D) Mott-Hubbard insulator Na_{0.96}V_{2}O_{5} and found that the spectra of the V 3d lower Hubbard band are strongly dependent on the temperature. We have calculated the one-particle spectral function of the one-dimensional t-J model at finite temperatures by exact diagonalization and compared them with the experimental results. Good overall agreement is obtained between experiment and theory. The strong finite temperature effects are discussed in terms of the existence of the ``Fermi surface'' of the spinon band.Comment: 4 pages, 3 figure

A one dimensional model for the prediction of extraction yields in a two phases modified twin-screw extruder

Solid/liquid extraction is performed on raw plant substrate with a modified twin-screw extruder (TSE) used as a thermo-mecanochemical reactor. Visual observations and experimental residence time distributions (RTD) are used to develop a solid transport model based on classical chemical engineering method. Modeled and experimental residence times are compared. The transport model is then coupled with a reactive extraction model in order to predict extraction yields

An estimate of the cross-frontal transport at the shelf break of the East China Sea with the Finite Volume Coastal Ocean Model

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C03012, doi:10.1029/2005JC003290.The Finite Volume Coastal Ocean Model (FVCOM) is used to estimate the onshore cross-frontal transport at the shelf break of the East China Sea. Boundary conditions of FVCOM are provided by the Princeton Ocean Model simulating ocean currents in the Yellow Sea and East China Sea realistically. One advantage of this study is that the unstructured triangular cell grid of FVCOM resolves complex bottom topography that may trigger Kuroshio frontal waves. It is anticipated that these nonlinear frontal waves enhance the exchange of seawater between the Kuroshio and shelf regions. Kuroshio frontal waves in the model are excited around the location where the bottom slope changes abruptly, and have the phase speed and amplitude consistent with those observed in the East China Sea. In addition, the model reproduces the onshore transport associated with growing frontal waves in the upper and lower layers. On the basis of passive tracer experiments, the annually averaged onshore-transport integrated along the shelf break is estimated to be 0.85 × 106 m3/s.This study was carried out when A. I. stayed at WHOI with the grant of Overseas Advanced Educational Research Practice Support Program supported by the Ministry of Education, Science and Culture, Japan. In addition, the Japan Society for the Promotion of Science supported this study through Grant-in-Aid for Scientific Research

Effects of Velocity Correlation on Early Stage of Free Cooling Process of Inelastic Hard Sphere System

The free cooling process in the inelastic hard sphere system is studied by analysing the data from large scale molecular dynamics simulations on a three dimensional system. The initial energy decay, the velocity distribution function, and the velocity correlation functions are calculated to be compared with theoretical predictions. The energy decay rate in the homogeneous cooling state is slightly but distinctively smaller than that expected from the independent collision assumption. The form of the one particle velocity distribution is found not to be stationary. These contradict to the predictions of the kinetic theory based on the Enskog-Boltzmann equation and suggest that the velocity correlation is already important in the early stage of homogeneous cooling state. The energy decay rate is analysed in terms of the velocity correlation.Comment: 9 pages (figures included). To be published in J. Phys. Soc. Jpn. Vol. 73 No. 1 (2004) Added two references and removed one. Changed the name of T_{L}. Added unit constants in Sec. 5 and

Charge-ordering and optical transitions of LiV2O5 and NaV2O5

We present the measurements of the polarized optical spectra of NaV2O5 and LiV2O5. In an energy range from 0.5 to 5.5 eV we observe similar peaks in the E parallel a spectra of LiV2O5 and NaV2O5, which suggests similar electronic structure along the a axis in both materials. On the other hand, we find an almost complete suppression of the peaks in sigma_b of LiV2O5 around 1 and 5 eV. We attribute this suppression to the charge localization originating from the existence of double-chain charge-ordering patterin in LiV2O5.Comment: 7 pages, 3 figures final version, to appear in PR

Optical properties of NaxV2O5

The optical properties of sodium-deficient NaxV2O5 (0.85 < x <1) single crystals are analyzed in the wide energy range, from 0.012 to 4.5 eV, using ellipsometry, infrared reflectivity, and Raman scattering techniques. The material remains insulating up to the maximal achieved hole concentration of about 15%. In sodium deficient samples the optical absorption peak associated to the fundamental electronic gap develops at about 0.44 eV. It corresponds to the transition between vanadium dxy and the impurity band, which forms in the middle of the pure NaV2O5 gap. Raman spectra measured with incident photon energy larger then 2 eV show strong resonant behavior, due to the presence of the hole-doping activated optical transitions, peaked at 2.8 eV.Comment: 7 pages, 4 fugures, to be published in PR

Discovery of a bright transient ultraluminous X-ray source Suzaku J1305-4931 in NGC 4945

This paper reports the discovery of a bright X-ray transient source, Suzaku J1305-4913, in the south-west arm of the nearby Seyfert II galaxy NGC 4945. It was detected at a 0.5 -- 10 keV flux of $2.2 \times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$ during the Suzaku observation conducted on 2006 January 15 -- 17, but was undetectable in a shorter observation on 2005 August 22 --23, with an upper limit of $1.7 \times 10^{-14}$ erg cm$^{-2}$ s$^{-1}$ (90% confidence level). At a distance of 3.7 Mpc, the bolometric luminosity of the source becomes $L_{\rm bol} = 4.4 \times 10^{39} \alpha$ erg s$^{-1}$, where $\alpha = (\cos 60^\circ / \cos i)$ and $i$ is the disk inclination. Therefore, the source is classified into so-called ultraluminous X-ray sources (ULXs). The time-averaged X-ray spectrum of the source is described by a multi-color disk model, with the innermost accretion disk temperature of $T_{\rm in} = 1.69_{-0.05}^{+0.06}$ keV. During the 2006 January observation, it varied by a factor of 2 in intensity, following a clear correlation of $L_{\rm bol} \propto T_{\rm in}^4$. It is inferred that the innermost disk radius $R_{\rm in}$ stayed constant at $R_{\rm in} = 79_{-3.9}^{+4.0} \alpha^{1/2}$ km, suggesting the presence of a standard accretion disk. Relating $R_{\rm in}$ with the last stable orbit around a non-rotating black hole yields a rather low black hole mass, $\sim 9 \alpha^{1/2}$ solar masses, which would imply that the source is shining at a luminosity of $\sim3 \alpha^{1/2}$ times the Eddington limit. These results can be better interpreted by invoking sub-Eddington emission from a rapidly spinning black hole with a mass of 20 -- 130 solar masses.Comment: 21 pages, 10 figures, Accepted for PASJ 2nd Suzaku special issu

A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra

(Abridged) We have searched for nuclear radio emission from a statistically complete sample of 40 Sc galaxies within 30 Mpc that are optically classified as star-forming objects, in order to determine whether weak AGNs might be present. Only three nuclear radio sources were detected, in NGC 864, NGC 4123, and NGC 4535. These galaxies have peak 6-cm radio powers of 10^{20} W/Hz at arcsecond resolution, while upper limits of the non-detected galaxies typically range from 10^{18.4} to 10^{20} W/Hz. The three nuclear radio sources all are resolved and appear to have diffuse morphologies, with linear sizes of ~300 pc. This strongly indicates that circumnuclear star formation has been detected in these three H II galaxies. Comparison with previous 20-cm VLA results for the detected galaxies shows that the extended nuclear radio emission has a flat spectrum in two objects, and almost certainly is generated by thermal emission from gas ionized by young stars in the centers of those galaxies. The 6-cm radio powers are comparable to predictions for thermal emission that are based on the nuclear H-alpha luminosities, and imply nuclear star formation rates of 0.08-0.8 solar masses/yr, while the low-resolution NRAO VLA Sky Survey implies galaxy-wide star formation rates of 0.3-1.0 solar masses/yr in stars above 5 solar masses. Although the presence of active nuclei powered by massive black holes cannot be definitively ruled out, the present results suggest that they are likely to be rare in these late-type galaxies with H II spectra.Comment: To appear in ApJ. 7 page

Two phase residence time distribution in a modified twin screw extruder

Biomass fractionation is performed with a modified Clextral twin-screw extruder used as a thermo-mechano-chemical reactor. This new process is firstly analyzed. Visual observations, residence time distributions, and global mass balances are used to obtain information about the process phenomena and their coupling. Residence time distributions (RTD) classical models are adopted to represent the experimental plots. The influence of continuous and discrete process parameters upon the RTD of the solid and liquid phases is analyzed