Gravitational collapse and equilibrium conditions of a toroidal vortex with thermal pressure

We found the equilibrium conditions for a self-gravitating toroidal vortex by taking thermal pressure into account. These conditions are shown to significantly differ from those for a disk or a sphere. The evolution of a thin vortex turns it into a compact vortex that loses mechanical stability for low masses at a polytropic index γ<4/3 but retains stability for sufficiently high masses and densities determined by the velocity circulation in the vortex.     

A Model of the Spraying of Drops from the Molten Surface of a Meteoroid in the Process of Ablation

An additional investigation has been carried out of the rational model (Aslanov, 2000) of the separation of drops from the tops of the unstable wave formation on the molten surface of a meteoroid. The ratio of the wavelength of unstable hydrodynamic disturbances to the diameter of drops has been calculated in a mathematically closed form. Particular theoretical estimates of the size of the region of spraying of molten drops agree with prevailing sizes given in the known classification of the forms of meteoroid fragmentation.     

The dynamical structure of dwarf elliptical galaxies

Deep imaging and long-slit spectroscopy was obtained for a sample of dwarf ellipticals in the Fornax cluster, NGC 5044 and NGC 5898 groups using the ESO VLT. The observational data extend out to typically 1.5–2 effective radii and indicate a kinematic dichotomy in the family of ellipticals. The observed stellar kinematics indicate a luminosity–velocity dispersion relation largely supporting Supernova-driven stellar mass loss scenarios for the formation of dwarf ellipticals. Stellar dynamical models favour dark matter halos with typical mass-to-light ratios in the range of 3 to 9 solar units. This revised version was published online in August 2006 with corrections to the Cover Date.     

The shape of the rotation curves of edge-on galaxies

We consider the effects of projection, internal absorption, and gas-or stellar-velocity dispersion on the measured rotation curves of galaxies with edge-on disks. Axisymmetric disk models clearly show that the rotational velocity in the inner galaxy is highly underestimated. As a result, an extended portion that imitates nearly rigid rotation appears. At galactocentric distances where the absorption is low (i.e., it does not exceed 0.3–0.5^m kpc^?1), the line profiles can have two peaks, and a rotation curve with minimum distortions can be obtained by estimating the position of the peak that corresponds to a higher rotational velocity. However, the high-velocity peak disappears in high-absorption regions and the actual shape of the rotation curve cannot be reproduced from line-of-sight velocity estimates. In general, the optical rotation curves for edge-on galaxies are of little use in reconstructing the mass distribution in the inner regions, particularly for galaxies with a steep velocity gradient in the central region. In this case, estimating the rotation velocities for outer (transparent) disk regions yields correct results.     

A search for high-redshift molecular absorption lines towards millimetre-loud, optically faint quasars

We describe initial results of a search for redshifted molecular absorption towards four millimetre-loud, optically faint quasars. A wide frequency bandwidth of up to 23 GHz per quasar was scanned using the Swedish–ESO Submillimetre Telescope at La Silla. Using a search list of commonly detected molecules, we obtained nearly complete redshift coverage up to   z _abs= 5  . The sensitivity of our data is adequate to have revealed absorption systems with characteristics similar to those seen in the four known redshifted millimetre-band absorption systems, but none were found. Our frequency-scan technique nevertheless demonstrates the value of wide-band correlator instruments for searches such as these. We suggest that a somewhat larger sample of similar observations should lead to the discovery of new millimetre-band absorption systems.     

Extreme Ultraviolet Emission Lines of ca xv in Solar and Laboratory Spectra

New R-matrix calculations of electron impact excitation rates in Caxv are used to derive theoretical electron density diagnostic emission line intensity ratios involving 2s ²2p ²–2s2p ³ transitions, specifically R ₁=I(208.70 Å)/I(200.98 Å), R ₂=I(181.91 Å)/I(200.98 Å), and R ₃=I(215.38 Å)/I(200.98 Å), for a range of electron temperatures (T _e=10^6.4–10^6.8 K) and densities (N _e=10⁹–10¹³ cm^–3) appropriate to solar coronal plasmas. Electron densities deduced from the observed values of R ₁, R ₂, and R ₃ for several solar flares, measured from spectra obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab, are found to be consistent. In addition, the derived electron densities are in excellent agreement with those determined from line ratios in Caxvi, which is formed at a similar electron temperature to Caxv. These results provide some experimental verification for the accuracy of the line ratio calculations, and hence the atomic data on which they are based. A set of eight theoretical Caxv line ratios involving 2s ²2p ²–2s2p ³ transitions in the wavelength range 140–216 Å are also found to be in good agreement with those measured from spectra of the TEXT tokamak plasma, for which the electron temperature and density have been independently determined. This provides additional support for the accuracy of the theoretical line ratios and atomic data.     

海带雌性原生质体的分离与培养

于1993年1月 - 1993年4月，为了制备遗传性纯一的基因工程受体，用酶法从海带雌配子体单性生殖系分离雌性单倍体原生质体。从皱纹盘鲍消化腺及消化器官提取出鲍酶，在25°C下、1％（W／V）的鲍酶与2％（W／V）的纤维素酶（Onozuka R－10）合用能有效解离单细胞和原生质体。海带雌性原生质体经2d培养再生了细胞壁。     

Immunological characterization of metallothionein in marine and freshwater fish

Metallothionein (MT) is a low-molecular-weight, cysteine-rich, metalbinding protein found in all vertebrates. The primary structure of the protein is evolutionary conserved, especially the location of cysteine-residues. There are nonetheless significant differences between MTs from different vertebrate classes, notably in major antigenic epitopes. Previous work has shown that MT from different fish species also differ. The objective of the present work was to characterize MT from temperate, sub-tropical and tropical fish species by their relative reactivities with two anti-fish MT antisera. One or both antisera cross-reacted with MT from all fish species investigated. Surprisingly, the relative reactivities of the two antisera with MT from species belonging to different taxonomic groups appeared to reflect differences at the level of family rather than differences between major phylogenetic lineages.