Ad M. T. Ciceronem.

Lovelace, R. V. E.; Wilkinson, C. H.

doi:10.1093/oseo/instance.00013416

Cited by 16 publications

(23 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We do not, however, see any clear gas motion towards the center as a result of the interaction of the counterstreaming components. An analytical study of two counterrotating gas disks lying one over the other predicts that the counterrotating gas should drag the corotating gas inward with equal masses of corotating and counterrotating gas accreting rapidly (Lovelace & Chou 1996). Although we see enhanced accretion for infall with prograde gas (I6), the amount of prograde gas in our test is small and cannot be expected to dramatically affect the accretion and inflow rate of the counterrotating gas.…”

Section: Comparison With Previous Workmentioning

confidence: 65%

NGC 4138: A Case Study in Counterrotating Disk Formation

Thakar

Ryden

Jore

et al. 1997

ApJ

View full text Add to dashboard Cite

The Sa(r) galaxy NGC 4138 has been recently found to contain an extensive counterrotating disk which appears to be still forming. Up to a third of the stars in the disk system may be on retrograde orbits. A counterrotating ring of H II regions, along with extended counterrotating H I gas, suggests that the retrograde material has been recently acquired in the gas phase and is still trickling in. Using numerical simulations, we have attempted to model the process by which the counterrotating mass has been accreted by this galaxy. We investigate two possibilities: continuous retrograde infall of gas, and a retrograde merger with a gas-rich dwarf galaxy. Both processes are successful in producing a counterrotating disk of the observed mass and dimensions without heating up the primary significantly. Contrary to our experience with a fiducial cold, thin primary disk, the gas-rich merger works well for the massive, compact primary disk of NGC 4138 even though the mass of the dwarf galaxy is a significant fraction of the mass of the primary disk. Although we have restricted ourselves mainly to coplanar infall and mergers, we report on one inclined infall simulation as well. We also explore the possibility that the Hα ring seen in the inner half of the disk is a consequence of counterrotating gas clouds colliding with corotating gas already present in the disk and forming stars in the process.

show abstract

Section: Comparison With Previous Workmentioning

confidence: 65%

NGC 4138: A Case Study in Counterrotating Disk Formation

Thakar

Ryden

Jore

et al. 1997

ApJ

View full text Add to dashboard Cite

show abstract

“…It appears that parasite-related factors that help the parasite to survive in hostile macrophages local milieu may be involved. The ability of Leishrnania parasites to withstand an acidic environment inside macrophages has led to the identification of acid phosphatases, namely (a) extracellularly secreted soluble acid phosphatase [23,24] and (b) membrane-bound acid phosphatase [8][9][10]. Our data indicate that the membrane-bound acid phosphatase activity of promastigotes from the virulent clone was significantly higher as compared to that from the avirulent clone.…”

Section: Discussionmentioning

confidence: 92%

Acid phosphatase activity of promastigotes of Leishmania donovani: a marker of virulence

Singla

Khuller

Vinayak

1992

FEMS Microbiology Letters

View full text Add to dashboard Cite

Seven cloned lines of promastigotes of Leishmania donovani (UR 6) were isolated by limiting dilution. One clone, UR6-C25, failed to multiply inside the macrophages of line J774G8 and thus was labelled as avirulent. Another, UR6-C24, multiplied inside macrophages, had a virulence index as high as 93 +/- 9.8 and was thus labelled as highly virulent. The other five clones had variable degree of virulence indices ranging from 46.4 +/- 5.8 to 67.6 +/- 3.5. No significant difference in the degrees of attachment of virulent and avirulent populations of promastigotes to macrophages was observed, suggesting no difference in the ligand utilised by these populations for attachment to the macrophages. Acid phosphatase activity of cloned promastigotes correlated with the degree of virulence. These data suggest that acid phosphatase activity could be used as a marker to differentiate avirulent from virulent populations of promastigotes of L. donovani.

show abstract

“…The existence of an open magnetic field region of the disk leads to the possibility of magnetically driven outflows. We analyze the magnetohydrodynamic (MHD) outflows and their back influence on the disk using the work on MHD outflows and magnetized disks by Lovelace, Berk, and Contopoulos (1991) Lovelace, Romanova, and Contopoulos (1993) (LRC), and Lovelace, Romanova, and Newman (1994)…”

Section: Introductionmentioning

confidence: 99%

Spin-up/spin-down of magnetized stars with accretion discs and outflows

Lovelace¹,

Romanova²,

Бисноватый-Коган³

1995

Monthly Notices of the Royal Astronomical Society

289

View full text Add to dashboard Cite

An investigation is made of disk accretion of matter onto a rotating star with an aligned dipole magnetic field. A new aspect of this work is that when the angular velocity of the star and disk differ substantially we argue that the B field linking the star and disk rapidly inflates to give regions of open field lines extending from the polar caps of the star and from the disk. The open field line region of the disk leads to the possibility of magnetically driven outflows. An analysis is made of the outflows and their back affect on the disk structure assuming an "α" turbulent viscosity model for the disk and a magnetic diffusivity comparable to this viscosity. The outflows are found to extend over a range of radial distances inward to a distance close to r to , which is the distance of the maximum of the angular rotation rate of the disk. We find that r to depends on the star's magnetic moment, the accretion rate, and the disk's magnetic diffusivity. The outflow regime is accompanied in general by a spin-up of the rotation rate of the star. When r to exceeds the star's corotation radius r cr = (GM/ω 2 * ) 1 3 , we argue that outflow solutions do not occur, but instead that "magnetic braking" of the star by the disk due to field-line twisting occurs in the vicinity of r cr . The magnetic braking solutions can give spin-up or spin-down (or no spin change) of the star depending mainly on the star's magnetic moment and the mass accretion rate. For a system with r to comparable to r cr , bimodal behavior is possible where extraneous perturbations (for example, intermittency of α, B field flux introduced from the companion star, or variations in the mass accretion rate) cause the system to flip between spin-up (with outflows, r to < r cr ) and spin-down (or spin-up) (with no outflows, r to > r cr ).

show abstract

Ad M. T. Ciceronem.

Cited by 16 publications

References 0 publications

NGC 4138: A Case Study in Counterrotating Disk Formation

NGC 4138: A Case Study in Counterrotating Disk Formation

Acid phosphatase activity of promastigotes of Leishmania donovani: a marker of virulence

Spin-up/spin-down of magnetized stars with accretion discs and outflows

Contact Info

Product

Resources

About