6,776 research outputs found
The slowing down of galaxy disks in dissipationless minor mergers
We have investigated the impact of dissipationless minor galaxy mergers on
the angular momentum of the remnant. Our simulations cover a range of initial
orbital characteristics and the system consists of a massive galaxy with a
bulge and disk merging with a much less massive (one-tenth or one-twentieth)
gasless companion which has a variety of morphologies (disk- or
elliptical-like) and central baryonic mass concentrations. During the process
of merging, the orbital angular momentum is redistributed into the internal
angular momentum of the final system; the internal angular momentum of the
primary galaxy can increase or decrease depending on the relative orientation
of the orbital spin vectors (direct or retrograde), while the initially
non-rotating dark matter halo always gains angular momentum. The specific
angular momentum of the stellar component always decreases independent of the
orbital parameters or morphology of the satellite, the decrease in the rotation
velocity of the primary galaxy is accompanied by a change in the anisotropy of
the orbits, and the ratio of rotation speed to velocity dispersion of the
merger remnant is lower than the initial value, not only due to an increase in
the dispersion but also to the slowing -down of the disk rotation. We briefly
discuss several astrophysical implications of these results, suggesting that
minor mergers do not cause a "random walk" process of the angular momentum of
the stellar disk component of galaxies, but rather a steady decrease. Minor
mergers may play a role in producing the large scatter observed in the
Tully-Fisher relation for S0 galaxies, as well as in the increase of the
velocity dispersion and the decrease in at large radii as observed
in S0 galaxies.Comment: 10 pages, 10 figures, accepted for publication in A&
Involvement of TIP60 acetyltransferase in intracellular Salmonella replication
<p>Abstract</p> <p>Background</p> <p><it>Salmonella </it>enterica is a facultative intracellular pathogen that replicates within a membrane-bound compartment termed <it>Salmonella </it>containing vacuole (SCV). The biogenesis of SCV requires <it>Salmonella </it>type III protein secretion/translocation system and their effector proteins which are translocated into host cells to exploit the vesicle trafficking pathways. SseF is one of these effectors required for SCV formation and Intracellular <it>Salmonella </it>replication through unknown mechanisms.</p> <p>Results</p> <p>In an attempt to identify host proteins that interact with SseF, we conduct a yeast two-hybrid screening of human cell cDNA library using SseF as the bait. We identified that TIP60, an acetyltransferase, interacts with SseF. We showed that the TIP60 acetylation activity was increased in the presence of SseF, and TIP60 was upregulated upon <it>Salmonella </it>infection. In addition, TIP60 is required for efficient intracellular <it>Salmonella </it>replication in macrophages.</p> <p>Conclusion</p> <p>Taken together, our data suggest that <it>Salmonella </it>may use SseF to exploit the host TIP60 acetyltransferase activity to promote efficient <it>Salmonella </it>replication inside host cells.</p
Effect of the changed electrolytic cell on the current efficiency in FFC Cambridge process
Low current efficiency of the FFC Cambridge process made it no obvious advantages in cost compared with the traditional process to produce metals. Effect of the changed electrolysis cell on the current efficiency has been studied. Put the cathode into an alumina tube with a hole can efficiently avoid short circuit and the cathode contaminated by carbon produced from graphite anode. The results show that the current efficiency can be improved greatly by reducing the electric field intensity in the electrolysis cell. The high background current is mainly caused by the electronic conductivity in the electrolysis cell. Otherwise, pollution of the cathode is avoided, the depletion of the anode sharply decreases and the deoxidation of the samples greatly improve when using the improvement electrolysis cell
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