Molecular rotation has attracted much attention with respect to the development of artificial molecular motors, in an attempt to mimic the intelligent and useful functions of biological molecular motors. Random motion of molecular rotators--for example the 180 degree flip-flop motion of a rotatory unit--causes a rotation of the local structure. Here, we show that such motion is controllable using an external electric field and demonstrate how such molecular rotators can be used as polarization rotation units in ferroelectric molecules. In particular, m-fluoroanilinium forms a hydrogen-bonding assembly with dibenzo[18]crown-6, which was introduced as the counter cation of [Ni(dmit)(2)](-) anions (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate). The supramolecular rotator of m-fluoroanilinium exhibited dipole rotation by the application of an electric field, and the crystal showed a ferroelectric transition at 348 K. These findings will open up new strategies for ferroelectric molecules where a chemically designed dipole unit enables control of the nature of the ferroelectric transition temperature.

Using three-dimensional general relativistic radiation magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk ( 10 7 K) is truncated near the black hole. Hot and less-dense regions, of which the gas temperature is 10 9 K and more than ten times higher than the radiation temperature (overheated regions), appear within the truncation radius. The overheated regions also appear above as well as below the disk, and sandwich the cold disk, leading to the effective Compton upscattering. The truncation radius is ∼ 30r g foṙ M ∼ L Edd /c 2 , where r g ,Ṁ , L Edd , c are the gravitational radius, mass accretion rate, Eddington luminosity, and light speed. Our results are consistent with observations of very high state, whereby the truncated disk is thought to be embedded in the hot rarefied regions. The truncation radius shifts inward to ∼ 10r g with increasing mass accretion rateṀ ∼ 100L Edd /c 2 , which is very close to an innermost stable circular orbit. This model corresponds to the slim disk state observed in ultra luminous X-ray sources. Although the overheated regions shrink if the Compton cooling effectively reduces the gas temperature, the sandwich-structure does not disappear at the range ofṀ 100L Edd /c 2 . Our simulations also reveal that the gas temperature in the overheated regions depends on black hole spin, which would be due to efficient energy tranpsport from black hole to disks through the Poynting flux, resulting gas heating.

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Using two-dimensional radiation hydrodynamic simulations, we investigate origin of the ultra fast outflows (UFOs) that are often observed in luminous active galactic nuclei (AGNs). We found that the radiation force due to the spectral lines generates strong winds (line-driven disk winds) that are launched from the inner region of accretion disks (∼ 30 Schwarzschild radii). A wide range of black hole masses (M BH ) and Eddington ratios (ε) was investigated to study conditions for causing the line-driven winds. For M BH = 10 6 -10 9 M ⊙ and ε = 0.1-0.7, funnel-shaped disk winds appear, in which dense matter is accelerated outward with an opening angle of 70-80• and with 10% of the light speed. If we observe the wind along its direction, the velocity, the column density, and the ionization state are consistent with those of the observed UFOs. As long as the obscuration by the torus does not affect the observations of X-ray bands, the UFOs could be statistically observed in about 13-28% of the luminous AGNs, which is not inconsistent with the observed ratio (∼ 40%). We also found that the results are insensitive to the X-ray luminosity and the density of the disk surface. Thus, we can conclude that the UFOs could exist in any luminous AGNs, such as narrow-line Seyfert 1s (NLS1s) and quasars with ε > 0.1, in which fast line-driven winds are associated.

We perform two-dimensional radiation hydrodynamical simulations of accretion flows onto a black hole (BH) with a mass of 10 3 M BH /M 10 6 in order to study rapid growth of BHs in the early Universe. For spherically symmetric flows, hyper-Eddington accretion onto the BH from outside the Bondi radius can occur unimpeded by radiation feedback only when the BH mass is higher than 10, where n ∞ and T ∞ are the density and temperature of ambient gas. Here, we study the properties of accretion flows exposed to anisotropic radiation from a nuclear accretion disk with a luminosity higher than the Eddington value (L Edd ) due to collimation toward the bipolar directions. We find that, unlike the spherically symmetric case, even less massive BHs with M BH < 10 4 M can be fed by surrounding gas at high accretion rates of L Edd /c 2 through the equatorial plane, while ionized regions expand to the polar directions producing hot outflows with T ∼ 10 5 K. For more massive BHs with M BH 5 × 10 5 M , neutral gas through the equatorial plane totally covers the central radiating region due to the non-radial gas motions, and thus the emergent radiation in all directions is blocked. Because of efficient recombination by hydrogen, the entire flow results in neutral and warm gas with T 8000 K. The central BH is fed through the equator at the averaged rate of ∼ 5 × 10 4 L Edd /c 2 , which corresponds to ∼ 50 % of the inflow rate from the Bondi radius. Moreover, radiation momentum absorbed by neutral hydrogen produces warm outflows toward the bipolar directions at ∼ 30 % of the BH feeding rate and with a typical velocity of 50 km s −1 .