844 research outputs found
Mining ancient microbiomes using selective enrichment of damaged DNA molecules
The identification of bona fide microbial taxa in microbiomes derived from ancient and historical samples is complicated by the unavoidable mixture between DNA from ante- and post-mortem microbial colonizers. One possibility to distinguish between these sources of microbial DNA is querying for the presence of age-associated degradation patterns typical of ancient DNA (aDNA). The presence of uracils, resulting from cytosine deamination, has been detected ubiquitously in aDNA retrieved from diverse sources, and used as an authentication criterion. Here, we employ a library preparation method that separates molecules that carry uracils from those that do not for a set of samples that includes Neandertal remains, herbarium specimens and archaeological plant remains
Transient simulation of gaseous particle/droplet laden flows in industrial-scale devices for flue gas cleaning including two-way mass and enthalpy coupling
Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The method of computational fluid dynamics (CFD) is
applied to spraying processes with strong enthalpy coupling.
Focus is brought to industrial scale applications in the field of
environmental engineering. A transient 3D finite volume solver
is used, wherein the disperse phase is modeled within an
Lagrangian framework. Two-way mass and enthalpy coupling
is taken into account. Resulting limitations of the traditional
sequential model droplet integration approach are discussed,
which potentially lead to thermodynamically inconsistant or
oscillatory solutions, especially in zones of dense spray. As an
alternative a combined sequential-simultaneous solution
algorithm is proposed. Thus obtained results show sufficient
aggreement with a validated test case. Application to industrial
scale reactors in the field of flue gas cleaning are demonstrated
exemplarily.cs201
Excitation of the molecular gas in the nuclear region of M82
We present high resolution HIFI spectroscopy of the nucleus of the
archetypical starburst galaxy M82. Six 12CO lines, 2 13CO lines and 4
fine-structure lines are detected. Besides showing the effects of the overall
velocity structure of the nuclear region, the line profiles also indicate the
presence of multiple components with different optical depths, temperatures and
densities in the observing beam. The data have been interpreted using a grid of
PDR models. It is found that the majority of the molecular gas is in low
density (n=10^3.5 cm^-3) clouds, with column densities of N_H=10^21.5 cm^-2 and
a relatively low UV radiation field (GO = 10^2). The remaining gas is
predominantly found in clouds with higher densities (n=10^5 cm^-3) and
radiation fields (GO = 10^2.75), but somewhat lower column densities
(N_H=10^21.2 cm^-2). The highest J CO lines are dominated by a small (1%
relative surface filling) component, with an even higher density (n=10^6 cm^-3)
and UV field (GO = 10^3.25). These results show the strength of multi-component
modeling for the interpretation of the integrated properties of galaxies.Comment: Accepted for publication in A&A Letter
First detection of ammonia in M82
We report the detection of the (J,K) = (1,1), (2,2), and (3,3) inversion
lines of ammonia (NH3) towards the south--western molecular lobe in M82. The
relative intensities of the ammonia lines are characterized by a rotational
temperature of T_rot=29+/-5 K which implies an average kinetic temperature of
T_kin~60 K. A Gaussian decomposition of the observed spectra indicates
increasing kinetic temperatures towards the nucleus of M82, consistent with
recent findings based on CO observations. The observations imply a very low NH3
abundance relative to H2, X(NH3)~5x10^(-10). We present evidence for a
decreasing NH3 abundance towards the central active regions in M82 and
interpret this abundance gradient in terms of photodissociation of NH3 in PDRs.
The low temperature derived here from NH3 also explains the apparent
underabundance of complex molecules like CH_3OH and HNCO, which has previously
been reported.Comment: 4 pages, 4 figures, accepted by ApJ
Postoperative drainage management and wound complications following resection of lower limb soft tissue tumors: a retrospective cohort study
A computational model unifies apparently contradictory findings concerning phantom pain
Amputation often leads to painful phantom sensations, whose pathogenesis is still unclear. Supported by experimental findings, an explanatory model has been proposed that identifies maladaptive reorganization of the primary somatosensory cortex (S1) as a cause of phantom pain. However, it was recently found that BOLD activity during voluntary movements of the phantom positively correlates with phantom pain rating, giving rise to a model of persistent representation. In the present study, we develop a physiologically realistic, computational model to resolve the conflicting findings. Simulations yielded that both the amount of reorganization and the level of cortical activity during phantom movements were enhanced in a scenario with strong phantom pain as compared to a scenario with weak phantom pain. These results suggest that phantom pain, maladaptive reorganization, and persistent representation may all be caused by the same underlying mechanism, which is driven by an abnormally enhanced spontaneous activity of deafferented nociceptive channels
A spinorial energy functional: critical points and gradient flow
On the universal bundle of unit spinors we study a natural energy functional
whose critical points, if dim M \geq 3, are precisely the pairs (g, {\phi})
consisting of a Ricci-flat Riemannian metric g together with a parallel
g-spinor {\phi}. We investigate the basic properties of this functional and
study its negative gradient flow, the so-called spinor flow. In particular, we
prove short-time existence and uniqueness for this flow.Comment: Small changes, final versio
VLBI observations of SN 2008iz: I. Expansion velocity and limits on anisotropic expansion
We present observations of the recently discovered supernova 2008iz in M82
with the VLBI High Sensitivity Array at 22 GHz, the Very Large Array at
frequencies of 1.4, 4.8, 8.4, 22 and 43 GHz, and the Chandra X-ray observatory.
The supernova was clearly detected on two VLBI images, separated by 11 months.
The source shows a ring-like morphology and expands with a velocity of ~23000
km/s. The most likely explosion date is in mid February 2008. The measured
expansion speed is a factor of ~2 higher than expected under the assumption
that synchrotron self-absorption dominates the light curve at the peak,
indicating that this absorption mechanism may not be important for the radio
emission. We find no evidence for an asymmetric explosion. The VLA spectrum
shows a broken power law, indicating that the source was still optically thick
at 1.4 GHz in April 2009. Finally, we report upper limits on the X-ray emission
from SN 2008iz and a second radio transient recently discovered by MERLIN
observations.Comment: accepted Astronomy & Astrophysics, 9 pages, 8 figures, also available
at http://www.mpifr-bonn.mpg.de/staff/abrunthaler/pub.shtm
HIFI spectroscopy of low-level water transitions in M82
We present observations of the rotational ortho-water ground transition, the
two lowest para-water transitions, and the ground transition of ionised
ortho-water in the archetypal starburst galaxy M82, performed with the HIFI
instrument on the Herschel Space Observatory. These observations are the first
detections of the para-H2O(111-000) (1113\,GHz) and ortho-H2O+(111-000)
(1115\,GHz) lines in an extragalactic source. All three water lines show
different spectral line profiles, underlining the need for high spectral
resolution in interpreting line formation processes. Using the line shape of
the para-H2O(111-000) and ortho-H2O+(111-000) absorption profile in conjunction
with high spatial resolution CO observations, we show that the (ionised) water
absorption arises from a ~2000 pc^2 region within the HIFI beam located about
~50 pc east of the dynamical centre of the galaxy. This region does not
coincide with any of the known line emission peaks that have been identified in
other molecular tracers, with the exception of HCO. Our data suggest that water
and ionised water within this region have high (up to 75%) area-covering
factors of the underlying continuum. This indicates that water is not
associated with small, dense cores within the ISM of M82 but arises from a more
widespread diffuse gas component.Comment: 5 pages, 4 figures. Accepted for publication in A&
A molecular line scan in the Hubble Deep Field North
We present a molecular line scan in the Hubble Deep Field North (HDF-N) that covers the entire 3mm window (79-115 GHz) using the IRAM Plateau de Bure Interferometer. Our CO redshift coverage spans z2. We reach a CO detection limit that is deep enough to detect essentially all z>1 CO lines reported in the literature so far. We have developed and applied different line searching algorithms, resulting in the discovery of 17 line candidates. We estimate that the rate of false positive line detections is ~2/17. We identify optical/NIR counterparts from the deep ancillary database of the HDF-N for seven of these candidates and investigate their available SEDs. Two secure CO detections in our scan are identified with star-forming galaxies at z=1.784 and at z=2.047. These galaxies have colors consistent with the `BzK' color selection and they show relatively bright CO emission compared with galaxies of similar dust continuum luminosity. We also detect two spectral lines in the submillimeter galaxy HDF850.1 at z=5.183. We consider an additional 9 line candidates as high quality. Our observations also provide a deep 3mm continuum map (1-sigma noise level = 8.6 μJy/beam). Via a stacking approach, we find that optical/MIR bright galaxies contribute only to <50% of the SFR density at 1<z<3, unless high dust temperatures are invoked. The present study represents a first, fundamental step towards an unbiased census of molecular gas in `normal' galaxies at high-z, a crucial goal of extragalactic astronomy in the ALMA era
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