Discovery of meteorites on a blue-ice field near the Frontier Mountains, North Victoria Land, Antarctica

A high concentration of meteorites were discovered on a blue ice field northeast of the Frontier Mountains. As a result of a systematic search, a total of 42 meteorites were recovered. The current glacial situation has evolved through various stages, which are discussed in relationship to the concentration of meteorites. Ice flow patterns are summarized. The chemical composition and terrestrial ages of the meteorites are discussed

The diffuse radio emission from the Coma cluster at 2.675 GHz and 4.85 GHz

We present new measurements of the diffuse radio halo emission from the Coma cluster of galaxies at 2.675 GHz and 4.85 GHz using the Effelsberg 100--m telescope. After correction for the contribution from point sources we derive the integrated flux densities for the halo source (Coma C), $S_{2.675 GHz}=(107\pm 28)mJy$ and $S_{4.85 GHz}=(26\pm 12)mJy$. These values verify the strong steepening of the radio spectrum of Coma C at high frequencies. Its extent strongly depends on frequency, at 4.85 GHz it is only marginally visible. The measurement at 4.85 GHz is the first flux density determination for Coma C at this high frequency. In order to quantify the spectral steepening we compare the expectations for the spectrum of Coma C with the observations, resorting to basic models for radio halo formation. The in--situ acceleration model provides the best fit to the data. From equipartition assumptions we estimate a magnetic field strength $B_{eq}=0.57 (1+k)^{0.26}\mu G$ in the intracluster medium of Coma, where k is the energy ratio of the positively and negatively charged particles. As a by--product of the 2.675 GHz observation we present a new flux density for the diffuse emission of the extended source 1253+275 ($S_{2.675GHz}=112\pm 10$). This measurement provides a smaller error range for the power--law fit to the spectrum ($\alpha=1.18\pm 0.02$) compared to previous investigations and yields an equipartition magnetic field strength of $B_{eq}=0.56 (1+k)^{0.24}\mu G$.Comment: 10 pages with 9 PostScript figures. Accepted for publication in A&A, latest revision includes minor changes at page proof correction stag

Rigid fibrescope Bonfils: use in simulated difficult airway by novices

<p>Abstract</p> <p>Background</p> <p>The Bonfils intubation fibrescope is a promising alternative device for securing the airway. We examined the success rate of intubation and the ease of use in standardized simulated difficult airway scenarios by physicians. We compared the Bonfils to a classical laryngoscope with Macintosh blade.</p> <p>Methods</p> <p>30 physicians untrained in the use of rigid fibrescopes but experienced in airway management performed endotracheal intubation in an airway manikin (SimMan, Laerdal, Kent, UK) with three different airway conditions. We evaluated the success rate using the Bonfils (Karl Storz, Tuttlingen, Germany) or the Macintosh laryngoscope, the time needed for securing the airway, and subjective rating of both techniques.</p> <p>Results</p> <p>In normal airway all intubations were successful using laryngoscope (100%) vs. 82% using the Bonfils (p < 0.05). In the scenario "tongue oedema" success rate using the Macintosh laryngoscope was 67% and 83% using the Bonfils. In the scenario "decreased cervical range of motion with jaw trismus", success rate using the Macintosh laryngoscope was 84% vs. 76%. In difficult airway scenarios time until airway was secured did not differ between the two devices. Use of Bonfils was rated "easier" in both difficult airway scenarios.</p> <p>Conclusion</p> <p>The Bonfils can be successfully used by physicians unfamiliar with this technique in an airway manikin. The airway could be secured with at least the same success rate as using a Macintosh laryngoscope in difficult airway scenarios. Use of the Bonfils did not delay intubation in the presence of a difficult airway. These results indicate that intensive special training is advised to use the Bonfils effectively in airway management.</p

Radio continuum spectra of galaxies in the Virgo cluster region

New radio continuum observations of galaxies in the Virgo cluster region at 4.85, 8.6, and 10.55 GHz are presented. These observations are combined with existing measurements at 1.4 and 0.325 GHz. The sample includes 81 galaxies were spectra with more than two frequencies could be derived. Galaxies that show a radio-FIR excess exhibit central activity (HII, LINER, AGN). The four Virgo galaxies with the highest absolute radio excess are found within 2 degrees of the center of the cluster. Galaxies showing flat radio spectra also host active centers. There is no clear trend between the spectral index and the galaxy's distance to the cluster center.Comment: 13 pages, 12 figures. Accepted for publication in A&

On the DM interpretation of the origin of non-thermal phenomena in galaxy clusters

(Abridged) We study the predictions of various annihilating Dark Matter (DM) models in order to interpret the origin of non-thermal phenomena in galaxy clusters. We consider three neutralino DM models with light (9 GeV), intermediate (60 GeV) and high (500 GeV) mass. The secondary particles created by neutralino annihilation produce a multi-frequency Spectral Energy Distribution (SED), as well as heating of the intracluster gas, that are tested against the observations available for the Coma cluster. The DM produced SEDs are normalized to the Coma radio halo spectrum. We find that it is not possible to interpret all non-thermal phenomena observed in Coma in terms of DM annihilation. The DM model with 9 GeV mass produces too small power at all frequencies, while the DM model with 500 GeV produces a large excess power at all frequencies. The DM model with 60 GeV and $\tau^{\pm}$ composition is consistent with the HXR and gamma-ray data but fails to reproduce the EUV and soft X-ray data. The DM model with 60 GeV and $b{\bar b}$ composition is always below the observed fluxes. The radio halo spectrum of Coma is well fitted only in the $b{\bar b}$ or light and intermediate mass DM models. The heating produced by DM annihilation in the center of Coma is always larger than the intracluster gas cooling rate for an NFW DM density profile and it is substantially smaller than the cooling rate only for a cored DM density profile in DM model with 9 GeV. We conclude that the possibility of interpreting the origin of non-thermal phenomena in galaxy clusters with DM annihilation models requires a low neutralino mass and a cored DM density profile. If we then consider the multimessenger constraints to the neutralino annihilation cross-section, it turns out that such scenario would also be excluded unless we introduce a substantial boost factor due to the presence of DM substructures.Comment: 9 pages, 6 figures, 2 Tables. Submitted to A&

Radio Halos From Simulations And Hadronic Models II: The Scaling Relations of Radio Halos

We use results from a constrained, cosmological MHD simulation of the Local Universe to predict radio halos and their evolution for a volume limited set of galaxy clusters and compare to current observations. The simulated magnetic field inside the clusters is a result of turbulent amplification within them, with the magnetic seed originating from star-burst driven, galactic outflows. We evaluate three models, where we choose different normalizations for the Cosmic Ray proton population within clusters. Similar to our previous analysis of the Coma cluster (Donnert et al. 2010), the radial profile and the morphological properties of observed radio halos can not be reproduced, even with a radially increasing energy fraction within the cosmic ray proton population. Scaling relations between X-ray luminosity and radio power can be reproduced by all models, however all models fail in the prediction of clusters with no radio emission. Also the evolutionary tracks of our largest clusters in all models fail to reproduce the observed bi-modality in radio luminosity. This provides additional evidence that the framework of hadronic, secondary models is disfavored to reproduce the large scale diffuse radio emission of galaxy clusters. We also provide predictions for the unavoidable emission of $\gamma$-rays from the hadronic models for the full cluster set. None of such secondary models is yet excluded by the observed limits in $\gamma$-ray emission, emphasizing that large scale diffuse radio emission is a powerful tool to constrain the amount of cosmic ray protons in galaxy clusters

Variable Expression of Cre Recombinase Transgenes Precludes Reliable Prediction of Tissue-Specific Gene Disruption by Tail-Biopsy Genotyping

The Cre/loxP-system has become the system of choice for the generation of conditional so-called knockout mouse strains, i.e. the tissue-specific disruption of expression of a certain target gene. We here report the loss of expression of Cre recombinase in a transgenic mouse strain with increasing number of generations. This eventually led to the complete abrogation of gene expression of the inserted Cre cDNA while still being detectable at the genomic level. Conversely, loss of Cre expression caused an incomplete or even complete lack of disruption for the protein under investigation. As Cre expression in the tissue of interest in most cases cannot be addressed in vivo during the course of a study, our findings implicate the possibility that individual tail-biopsy genotypes may not necessarily indicate the presence or absence of gene disruption. This indicates that sustained post hoc analyses in regards to efficacy of disruption for every single study group member may be required

Clusters of galaxies : observational properties of the diffuse radio emission

Clusters of galaxies, as the largest virialized systems in the Universe, are ideal laboratories to study the formation and evolution of cosmic structures...(abridged)... Most of the detailed knowledge of galaxy clusters has been obtained in recent years from the study of ICM through X-ray Astronomy. At the same time, radio observations have proved that the ICM is mixed with non-thermal components, i.e. highly relativistic particles and large-scale magnetic fields, detected through their synchrotron emission. The knowledge of the properties of these non-thermal ICM components has increased significantly, owing to sensitive radio images and to the development of theoretical models. Diffuse synchrotron radio emission in the central and peripheral cluster regions has been found in many clusters. Moreover large-scale magnetic fields appear to be present in all galaxy clusters, as derived from Rotation Measure (RM) studies. Non-thermal components are linked to the cluster X-ray properties, and to the cluster evolutionary stage, and are crucial for a comprehensive physical description of the intracluster medium. They play an important role in the cluster formation and evolution. We review here the observational properties of diffuse non-thermal sources detected in galaxy clusters: halos, relics and mini-halos. We discuss their classification and properties. We report published results up to date and obtain and discuss statistical properties. We present the properties of large-scale magnetic fields in clusters and in even larger structures: filaments connecting galaxy clusters. We summarize the current models of the origin of these cluster components, and outline the improvements that are expected in this area from future developments thanks to the new generation of radio telescopes.Comment: Accepted for the publication in The Astronomy and Astrophysics Review. 58 pages, 26 figure

Radio Halos From Simulations And Hadronic Models I: The Coma cluster

We use the results from a constrained, cosmological MHD simulation of the Local Universe to predict the radio halo and the gamma-ray flux from the Coma cluster and compare it to current observations. The simulated magnetic field within the Coma cluster is the result of turbulent amplification of the magnetic field during build-up of the cluster. The magnetic seed field originates from star-burst driven, galactic outflows. The synchrotron emission is calculated assuming a hadronic model. We follow four approaches with different distributions for the cosmic-ray proton (CRp) population within galaxy clusters. The radial profile the radio halo can only be reproduced with a radially increasing energy fraction within the cosmic ray proton population, reaching $>$100% of the thermal energy content at $\approx$ 1Mpc, e.g. the edge of the radio emitting region. Additionally the spectral steepening of the observed radio halo in Coma cannot be reproduced, even when accounting for the negative flux from the thermal SZ effect at high frequencies. Therefore the hadronic models are disfavored from present analysis. The emission of $\gamma$-rays expected from our simulated coma is still below the current observational limits (by a factor of $\sim$6) but would be detectable in the near future.Comment: Submitted to MNRAS, 5pages, 3 figures, 1 tabl

Nonthermal radiation mechanisms

In this paper we review the possible radiation mechanisms for the observed non-thermal emission in clusters of galaxies, with a primary focus on the radio and hard X-ray emission. We show that the difficulty with the non-thermal, non-relativistic Bremsstrahlung model for the hard X-ray emission, first pointed out by Petrosian (2001) using a cold target approximation, is somewhat alleviated when one treats the problem more exactly by including the fact that the background plasma particle energies are on average a factor of 10 below the energy of the non-thermal particles. This increases the lifetime of the non-thermal particles, and as a result decreases the extreme energy requirement, but at most by a factor of three. We then review the synchrotron and so-called inverse Compton emission by relativistic electrons, which when compared with observations can constrain the value of the magnetic field and energy of relativistic electrons. This model requires a low value of the magnetic field which is far from the equipartition value. We briefly review the possibilities of gamma-ray emission and prospects for GLAST observations. We also present a toy model of the non-thermal electron spectra that are produced by the acceleration mechanisms discussed in an accompanying paper.Comment: 17 pages, 6 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 10; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke