702 research outputs found
Complex diffuse radio emission in the merging PLANCK ESZ cluster Abell 3411
We present VLA radio and Chandra X-ray observations of the merging galaxy
cluster Abell 3411. For the cluster, we find an overall temperature of 6.4 keV
and an X-ray luminosity of 2.8 x 10^{44} erg s^{-1} between 0.5 and 2.0 keV.
The Chandra observation reveals the cluster to be undergoing a merger event.
The VLA observations show the presence of large-scale diffuse emission in the
central region of the cluster, which we classify as a 0.9 Mpc size radio halo.
In addition, a complex region of diffuse, polarized emission is found in the
southeastern outskirts of the cluster, along the projected merger axis of the
system. We classify this region of diffuse emission as a radio relic. The total
extent of this radio relic is 1.9 Mpc. For the combined emission in the cluster
region, we find a radio spectral index of -1.0 \pm 0.1 between 74 MHz and 1.4
GHz. The morphology of the radio relic is peculiar, as the relic is broken up
into five fragments. This suggests that the shock responsible for the relic has
been broken up due to interaction with a large-scale galaxy filament connected
to the cluster or other substructures in the ICM. Alternatively, the complex
morphology reflects the presence of electrons in fossil radio bubbles that are
re-accelerated by a shock.Comment: Accepted for publication in ApJ, 8 pages, 5 figure
Electron Microscopic Analysis and Structural Characterization of Novel NADP(H)-Containing Methanol:N,N'-Dimethyl-4-Nitrosoaniline Oxidoreductases from the Gram-Positive Methylotrophic Bacteria Amycolatopsis methanolica and Mycobacterium gastri MB19
Electron Microscopic Analysis and Structural Characterization of Novel NADP(H)-Containing Methanol:N,N'-Dimethyl-4-Nitrosoaniline Oxidoreductases from the Gram-Positive Methylotrophic Bacteria Amycolatopsis methanolica and Mycobacterium gastri MB19
PathOrganic – Risks and Recommendations Regarding Human Pathogens in Organic Vegetable Production Chains
PathOrganic assesses risks associated with the consumption of fresh and minimally
processed vegetables due to the prevalence of bacterial human pathogens in plant
produce. The project evaluates whether organic production poses a risk on food safety,
taking into consideration sources of pathogen transmission (e.g. animal manure).
The project also explores whether organic versus conventional production practices
may reduce the risk of pathogen manifestation. In Europe, vegetable-linked outbreaks
are not well investigated. A conceptual model together with novel sampling strategies
and specifically adjusted methods provides the basis for large-scale surveys of organically
grown plant produce in five European countries. Critical control points are
determined and evaluated and factors contributing to a food safety problem are analyzed
in greenhouse and field experiments. The project aims at developing a quantitative
risk assessment model and at formulating recommendations for improving food
safety in organic vegetable production
Mapping In Vivo Tumor Oxygenation within Viable Tumor by 19F-MRI and Multispectral Analysis
AbstractQuantifying oxygenation in viable tumor remains a major obstacle toward a better understanding of the tumor microenvironment and improving treatment strategies. Current techniques are often complicated by tumor heterogeneity. Herein, a novel in vivo approach that combines 19F magnetic resonance imaging (19F-MRI)R1 mapping with diffusionbased multispectral (MS) analysis is introduced. This approach restricts the partial pressure of oxygen (pO2) measurements to viable tumor, the tissue of therapeutic interest. The technique exhibited sufficient sensitivity to detect a breathing gas challenge in a xenograft tumor model, and the hypoxic region measured by MS 19F-MRI was strongly correlated with histologic estimates of hypoxia. This approach was then applied to address the effects of antivascular agents on tumor oxygenation, which is a research question that is still under debate. The technique was used to monitor longitudinal pO2 changes in response to an antibody to vascular endothelial growth factor (B20.4.1.1) and a selective dual phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor (GDC-0980). GDC-0980 reduced viable tumor pO2 during a 3-day treatment period, and a significant reduction was also produced by B20.4.1.1. Overall, this method provides an unprecedented view of viable tumor pO2 and contributes to a greater understanding of the effects of antivascular therapies on the tumor's microenvironment
Reaching thermal noise at ultra-low radio frequencies: the Toothbrush radio relic downstream of the shock front
Ultra-low frequency observations (<100 MHz) are particularly challenging
because they are usually performed in a low signal-to-noise ratio regime due to
the high sky temperature and because of ionospheric disturbances whose effects
are inversely proportional to the observing frequency. Nonetheless, these
observations are crucial to study the emission from low-energy populations of
cosmic rays. We aim to obtain the first thermal-noise limited (~ 1.5 mJy/beam)
deep continuum radio map using the LOFAR Low Band Antenna (LBA) system. Our
demonstration observation targeted the galaxy cluster RX J0603.3+4214 (the
"Toothbrush" cluster). We used the resulting ultra-low frequency (58 MHz) image
to study cosmic-ray acceleration and evolution in the post shock region, as
well as their relation with the presence of a radio halo. We describe the data
reduction we have used to calibrate LOFAR LBA observations. The resulting image
is combined with observations at higher frequencies (LOFAR 150 MHz and VLA 1500
MHz) to extract spectral information. We obtained the first thermal-noise
limited image from an observation carried out with the LOFAR LBA system using
all Dutch stations at a central frequency of 58 MHz. With 8 hours of data, we
reached an rms noise of 1.3 mJy/beam at a resolution of 18" x 11". The
procedure we have developed is an important step forward towards routine
high-fidelity imaging with the LOFAR LBA. The analysis of the radio spectra
shows that the radio relic extends to distances of 800 kpc downstream from the
shock front, larger than what allowed by electron cooling time. Furthermore,
the shock wave started accelerating electrons already at a projected distance
of <300 kpc from the crossing point of the two clusters. These results can be
explained if electrons are reaccelerated downstream by background turbulence
possibly combined with projection effects.Comment: 15 pages, 19 figures, accepted A&
Discovery of a Radio Halo (and Relic) in a M 500< 2 × 1014M o˙Cluster
Radio halos are diffuse synchrotron sources observed in dynamically unrelaxed galaxy clusters. Current observations and models suggest that halos trace turbulent regions in the intracluster medium where mildly relativistic particles are reaccelerated during cluster mergers. Due to the higher luminosities and detection rates with increasing cluster mass, radio halos have been mainly observed in massive systems (M500 ≳ 5 × 1014M⊙). Here, we report the discovery of a radio halo with a largest linear scale of ≃750 kpc in PSZ2G145.92-12.53 (z = 0.03) using LOw Frequency ARray (LOFAR) observations at 120-168 MHz. With a mass of M500=(1.9 ± 0.2) × 1014M⊙ and a radio power at 150 MHz of P150=(3.5 ± 0.7) × 1023 W Hz-1, this is the least powerful radio halo in the least massive cluster discovered to date. Additionally, we discover a radio relic with a mildly convex morphology at ∼1.7 Mpc from the cluster center. Our results demonstrate that LOFAR has the potential to detect radio halos even in low-mass clusters, where the expectation to form them is very low (∼5%) based on turbulent reacceleration models. Together with the observation of large samples of clusters, this opens the possibility to constrain the low end of the power-mass relation of radio halos
High-resolution, High-sensitivity, Low-frequency uGMRT View of Coma Cluster of Galaxies
We present high-resolution, high-sensitivity upgraded Giant Metrewave Radio Telescope observations of the Coma cluster (A1656) at 250-500 MHz and 550-850 MHz. At 250-500 MHz, 135 sources have extensions >0.'45 (with peak-to-local-noise ratio >4). Of these, 24 sources are associated with Coma-member galaxies. In addition, we supplement this sample of 24 galaxies with 20 ram pressure stripped (RPS) galaxies from (Chen et al. 2020, eight are included in the original extended radio source sample) and an additional five are detected and extended. We present radio morphologies, radio spectra, spectral index maps, and equipartition properties for these two samples. In general, we find the equipartition properties lie within a narrow range (e.g., Pmin = 1-3 × 10- 13 dynes cm-2). Only NGC 4874, one of the two brightest central Coma cluster galaxies, has a central energy density and pressure about five times higher and a radio source age about 50% lower than that of the other Coma galaxies. We find a diffuse tail of radio emission trailing the dominant galaxy of the merging NGC 4839 group that coincides with the slingshot tail seen in X-rays. The southwestern radio relic, B1253+275, has a large extent ≍32' × 10' (≃1.08 × 0.34 Mpc2). For NGC 4789, whose long radio tails merge into the relic and may be a source of its relativistic seed electrons, we find a transverse radio spectral gradient, a steepening from southwest to northeast across the width of the radio source. Finally, radio morphologies of the extended and RPS samples suggest that these galaxies are on their first infall into Coma on (predominantly) radial orbits
Pest categorisation of Ips cembrae
The Panel on Plant Health performed a pest categorisation of the large larch bark beetle, Ips cembrae
(Heer) (Coleoptera: Curculionidae, Scolytinae), for the EU. I. cembrae is a well-defined and
distinguishable species, native to Europe and recognised mainly as a pest of larch (Larix spp.) and
occasionally of pine (Pinus spp.) and spruce (Picea spp.). It is distributed in 16 Member States of the
EU and listed in Annex IIB of Council Directive 2000/29/EC. Protected zones are in place in Greece,
Ireland and the United Kingdom (Northern Ireland and Isle of Man). Wood, wood products, bark and
wood packaging material are considered as pathways for this pest, which is also able to disperse by
flight. The insects normally establish on fallen or weakened trees but, when their populations are high,
can also mass-attack healthy trees. The males produce aggregation pheromones that attract
conspecifics of both sexes. The insects also inoculate pathogenic fungi to their hosts. There are one to
two generations per year. Before establishing their broods, the young adults need to proceed to
maturation feeding either within the bark of the tree where they developed or in 2–18 years old twigs.
I. cembrae has been expanding its geographical range in Europe during the second half of the 20th
century. Sanitary thinning or clear felling is the major control methods. Quarantine measures are
implemented to prevent entry in the protected zones. All criteria for consideration as potential
protected zone quarantine pest are met. The criteria for considering I. cembrae as a potential
regulated non-quarantine pest are not met since plants for planting are not viewed as a major
pathway
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