385 research outputs found
Vibrational mode frequency correction of liquid water in density functional theory molecular dynamics simulations with van der Waals correction
The dielectric function profile across the water interface through surface-specific vibrational spectroscopy and simulations
AGN feedback and gas mixing in the core of NGC 4636
Chandra observations of NGC 4636 show disturbances in the galaxy X-ray halo,
including arm-like high surface brightness features (tentatively identified as
AGN driven shocks) and a possible cavity on the west side of the galaxy core.
We present Chandra and XMM spectral maps of NGC 4636 which confirm the presence
of the cavity and show it to be bounded by the arm features. The maps also
reveal a ~15 kpc wide plume of low temperature, high abundance gas extending
25-30 kpc to the southwest of the galaxy. The cavity appears to be embedded in
this plume, and we interpret the structure as being entrained gas drawn out of
the galaxy core during previous episodes of AGN activity. The end of the plume
is marked by a well defined edge, with significant falls in surface brightness,
temperature and abundance, indicating a boundary between galaxy and
group/cluster gas. This may be evidence that as well as preventing gas cooling
through direct heating, AGN outbursts can produce significant gas mixing,
disturbing the temperature structure of the halo and transporting metals out
from the galaxy into the surrounding intra-group medium.Comment: 4 Pages, 2 colour figures, accepted for publication in ApJ Letters.
Version with high quality images at
http://hea-www.harvard.edu/~ejos/files/N4636_hires.pd
Captures of Red Giant Stars by Black Holes in Elliptical Galaxies: Feedback to the Hot Gas
The highly disturbed hot gas in elliptical galaxies, as revealed in many {\em
Chandra} X-ray images, implies a source of energy in the galactic nucleus. In
some elliptical galaxies faint X-ray ``ghost'' cavities appear without
corresponding radio lobes. It has been suggested that ghost cavities are caused
by short-lived activity with a timescale of years, but this is
difficult to understand within the popular paradigm of active galactic nuclei.
We suggest an episode model for ghost cavities, invoking captures of red giant
stars by the black hole located at the center of the elliptical galaxies at a
typical rate of yr per galaxy. The accretion of tidally
disrupted red giant stars onto the black hole powers activity in a timescale of
a few years. The total energy channeled into the jet/outflow during the cooling
time of the hot gas is erg, which is the typical work required
to form the observed cavities. In this scenario, the faint cavities are
produced by the feedback following accretion of the debris of the captured red
giant stars onto the black holes. We apply the present model to several
elliptical galaxies and find that it can explain the formation of the ghost
cavities. This model can be tested in the future by comparisons between radio
and X-ray observations.Comment: 4 pages in emulateapj5.sty. to Appear in ApJ Letter
Scaling Mass Profiles around Elliptical Galaxies Observed with Chandra and XMM-Newton
We investigated the dynamical structure of 53 elliptical galaxies, based on
the {\it Chandra} archival X-ray data. In X-ray luminous galaxies, a
temperature increases with radius and a gas density is systematically higher at
the optical outskirts, indicating a presence of a significant amount of the
group-scale hot gas. In contrast, X-ray dim galaxies show a flat or declining
temperature profile against radius and the gas density is relatively lower at
the optical outskirts. Thus it is found that X-ray bright and faint elliptical
galaxies are clearly distinguished by the temperature and gas density profile.
The mass profile is well scaled by a virial radius rather than an
optical-half radius , and is quite similar at
between X-ray luminous and dim galaxies, and smoothly connects to those of
clusters of galaxies. At the inner region of or
, the mass profile well traces a stellar mass with a constant
mass-to-light ratio of .
ratio of X-ray bright galaxies rises up steeply beyond , and thus
requires a presence of massive dark matter halo. From the deprojection analysis
combined with the {\it XMM-Newton} data, we found that X-ray dim galaxies, NGC
3923, NGC 720, and IC 1459, also have a high ratio of 20--30 at
20 kpc, comparable to that of X-ray luminous galaxies. Therefore, dark matter
is indicated to be common in elliptical galaxies, and their distribution almost
follows the NFW profile, as well as galaxy clusters.Comment: 33 pages, 11 figures, to appear in ApJ 636 No.2, ApJ 10 January 200
Vibrational couplings and energy transfer pathways of water's bending mode
Yu, CC., Chiang, KY., Okuno, M. et al. Vibrational couplings and energy transfer pathways of waterâs bending mode. Nat Commun 11, 5977 (2020). https://doi.org/10.1038/s41467-020-19759-
Morphine activates neuroinflammation in a manner parallel to endotoxin
Opioids create a neuroinflammatory response within the CNS, compromising opioid-induced analgesia and contributing to various unwanted actions. How this occurs is unknown but has been assumed to be via classic opioid receptors. Herein, we provide direct evidence that morphine creates neuroinflammation via the activation of an innate immune receptor and not via classic opioid receptors. We demonstrate that morphine binds to an accessory protein of Toll-like receptor 4 (TLR4), myeloid differentiation protein 2 (MD-2), thereby inducing TLR4 oligomerization and triggering proinflammation. Small-molecule inhibitors, RNA interference, and genetic knockout validate the TLR4/MD-2 complex as a feasible target for beneficially modifying morphine actions. Disrupting TLR4/MD-2 proteinâprotein association potentiated morphine analgesia in vivo and abolished morphine-induced proinflammation in vitro, the latter demonstrating that morphine-induced proinflammation only depends on TLR4, despite the presence of opioid receptors. These results provide an exciting, nonconventional avenue to improving the clinical efficacy of opioids.Xiaohui Wang, Lisa C. Loram, Khara Ramos, Armando J. de Jesus, Jacob Thomas, Kui Cheng, Anireddy Reddy, Andrew A. Somogyi, Mark R. Hutchinson, Linda R. Watkins and Hang Yi
Radio Bubbles in Clusters
We extend our earlier work on cluster cores with distinct radio bubbles,
adding more active bubbles, i.e. those with Ghz radio emission, to our sample,
and also investigating ``ghost bubbles,'' i.e. those without GHz radio
emission. We have determined k, which is the ratio of the total particle energy
to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on
the ages of the active bubbles confirm that the ratio of the energy factor, k,
to the volume filling factor, f lies within the range 1 < k/f < 1000. In the
assumption that there is pressure equilibrium between the radio-emitting plasma
and the surrounding thermal X-ray gas, none of the radio lobes has
equipartition between the relativistic particles and the magnetic field. A
Monte-Carlo simulation of the data led to the conclusion that there are not
enough bubbles present in the current sample to be able to determine the shape
of the population. An analysis of the ghost bubbles in our sample showed that
on the whole they have higher upper limits on k/f than the active bubbles,
especially when compared to those in the same cluster. A study of the Brightest
55 cluster sample shows that 17, possibly 20, clusters required some form of
heating as they have a short central cooling time, t_cool < 3 Gyr, and a large
central temperature drop, T_centre/T_outer< 1/2. Of these between 12 (70 per
cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle
of bubbles is large in such clusters and that they can play a major role in the
heating process.Comment: 12 pages, Accepted for publication in MNRA
HST/ACS observations of shell galaxies: inner shells, shell colours and dust
AIM:Learn more about the origin of shells and dust in early type galaxies.
METHOD: V-I colours of shells and underlying galaxies are derived, using HST
Advanced Camera for Surveys (ACS) data. A galaxy model is made locally in
wedges and subtracted to determine shell profiles and colours. We applied
Voronoi binning to our data to get smoothed colour maps of the galaxies.
Comparison with N-body simulations from the literature gives more insight to
the origin of the shell features. Shell positions and dust characteristics are
inferred from model galaxy subtracted images. RESULT: The ACS images reveal
shells well within the effective radius in some galaxies (at 1.7 kpc in the
case of NGC 5982). In some cases, strong nuclear dust patches prevent detection
of inner shells. Most shells have colours which are similar to the underlying
galaxy. Some inner shells are redder than the galaxy. All six shell galaxies
show out of dynamical equilibrium dust features, like lanes or patches, in
their central regions. Our detection rate for dust in the shell ellipticals is
greater than that found from HST archive data for a sample of normal early-type
galaxies, at the 95% confidence level. CONCLUSIONS: The merger model describes
better the shell distributions and morphologies than the interaction model. Red
shell colours are most likely due to the presence of dust and/or older stellar
populations. The high prevalence and out of dynamical equilibrium morphologies
of the central dust features point towards external influences being
responsible for visible dust features in early type shell galaxies. Inner
shells are able to manifest themselves in relatively old shell systems.Comment: accepted by A&A; 36 Figures, 25 pages. A version with full resolution
Figures can be found here: http://www.astro.rug.nl/~sikkema/shells.p
Effects of APETALA2 on embryo, endosperm, and seed coat development determine seed size in Arabidopsis
Arabidopsis APETALA2 (AP2) controls seed mass maternally, with ap2 mutants producing larger seeds than wild type. Here, we show that AP2 influences development of the three major seed compartments: embryo, endosperm, and seed coat. AP2 appears to have a significant effect on endosperm development. ap2 mutant seeds undergo an extended period of rapid endosperm growth early in development relative to wild type. This early expanded growth period in ap2 seeds is associated with delayed endosperm cellularization and overgrowth of the endosperm central vacuole. The subsequent period of moderate endosperm growth is also extended in ap2 seeds largely due to persistent cell divisions at the endosperm periphery. The effect of AP2 on endosperm development is mediated by different mechanisms than parent-of-origin effects on seed size observed in interploidy crosses. Seed coat development is affected; integument cells of ap2 mutants are more elongated than wild type. We conclude that endosperm overgrowth and/or integument cell elongation create a larger postfertilization embryo sac into which the ap2 embryo can grow. Morphological development of the embryo is initially delayed in ap2 compared with wild-type seeds, but ap2 embryos become larger than wild type after the bent-cotyledon stage of development. ap2 embryos are able to fill the enlarged postfertilization embryo sac, because they undergo extended periods of cell proliferation and seed filling. We discuss potential mechanisms by which maternally acting AP2 influences development of the zygotic embryo and endosperm to repress seed size
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