Relativistic ejecta from XRF 060218 and the rate of cosmic explosions

Over the last decade, long-duration gamma-ray bursts (GRBs) including the subclass of X-ray flashes (XRFs) have been revealed to be a rare variety of Type Ibc supernova (SN). While all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by many orders of magnitude. The essential physical process that causes a dying star to produce a GRB or XRF, and not just an SN, remains the crucial open question. Here we present radio and X-ray observations of XRF 060218 (associated with SN 2006aj), the second nearest GRB identified to-date, which allow us to measure its total energy and place it in the larger context of cosmic explosions. We show that this event is 100 times less energetic but ten times more common than cosmological GRBs. Moreover, it is distinguished from ordinary Type Ibc SNe by the presence of 10^48 erg coupled to mildly-relativistic ejecta, along with a central engine (an accretion-fed, rapidly rotating compact source) which produces X-rays for weeks after the explosion. This suggests that the production of relativistic ejecta is the key physical distinction between GRBs/XRFs and ordinary SNe, while the nature of the central engine (black hole or magnetar) may distinguish typical bursts from low-luminosity, spherical events like XRF 060218.Comment: To appear in Nature on August 31 2006 (15 pages, 3 figures, 1 table, including Supplementary Information

Radio emission from Supernova Remnants

The explosion of a supernova releases almost instantaneously about 10^51 ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from a SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critical discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve further study, and analyzing the prospects for future research with the latest generation radio telescopes.Comment: Revised version. 48 pages, 15 figure

Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo

We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--$1.0 M_\odot$, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.

The von Mises omega(2)-statistic and the bootstrap

The closeness of the distribution functions of the von Mises w(2)-statistic for sampling from a continuous distribution and for sampling from a uniform discrete distribution is estimated. Its relation to the bootstrap is discussed

Von Mises omega(2)-statistic and the generalized Bayesian bootstraps

The uniform distance between the distribution functions of the von Mises omega(2)-statistic for sampling from a continuous distribution and of the `'generalized Bayesian omega(2)-statistic'' for sampling from the uniform distribution on a finite number of points is estimated. Application to the generalized Bayesian bootstraps is discussed

Normal approximation of U-statistics in Hilbert space

Let {U-n}, n = 1,2,..., be Hilbert space H-valued U-statistics with kernel Phi(.,.), corresponding to a sequence of observations (random variables) X-1,X-2,.... The rate of convergence on balls in the central limit theorem for (U-n) is investigated. The obtained estimate is of order n(-1/2) and depends explicitly on E parallel to Phi(X-1,X-2)parallel to(3) and on the trace and the first nine eigenvalues of the covariance operator of E(Phi(X-1,X-2)\textbackslash{}X-1)

3-Aminopropylsilane-modified iron oxide nanoparticles for contrast-enhanced magnetic resonance imaging of liver lesions induced by Opisthorchis felineus

Alexander M Demin,1,* Alexandra G Pershina,2,3,* Vladimir V Ivanov,2 Kseniya V Nevskaya,2 Oleg B Shevelev,4 Artyom S Minin,5 Iliya V Byzov,5 Alexey E Sazonov,2 Victor P Krasnov,1 Ludmila M Ogorodova2 1Postovsky Institute of Organic Synthesis of RAS (Ural Branch), Yekaterinburg, 2Siberian State Medical University, 3Russian National Research Tomsk Polytechnic University, Tomsk, 4Institute of Cytology and Genetics SB RAS, Novosibirsk, 5Miheev Institute of Metal Physics of RAS (Ural Branch), Yekaterinburg, Russia *These authors contributed equally to this work Purpose: Liver fluke causes severe liver damage in an infected human. However, the infection often remains neglected due to the lack of pathognomonic signs. Nanoparticle-enhanced magnetic resonance imaging (MRI) offers a promising technique for detecting liver lesions induced by parasites.Materials and methods: Surface modification of iron oxide nanoparticles produced by coprecipitation from a solution of Fe3+ and Fe2+ salts using 3-aminopropylsilane (APS) was carried out. The APS-modified nanoparticles were characterized by transmission electron microscopy, fourier transform infrared spectroscopy, and thermogravimetric analysis . Magnetic resonance properties of MNPs were investigated in vitro and in vivo.Results: The amount of APS grafted on the surface of nanoparticles (0.60±0.06 mmol g-1) was calculated based on elemental analysis and infrared spectroscopy data. According to transmission electron microscopy data, there were no essential changes in the structure of nanoparticles during the modification. The APS-modified nanoparticles exhibit high magnetic properties; the calculated relaxivity r2 was 271 mmol-1 s-1. To obtain suspension with optimal hydrodynamic characteristics, amino groups on the surface of nanoparticles were converted into an ionic form with HCl. Cellular uptake of modified nanoparticles by rat hepatoma cells and human monocytes in vitro was 74.1±4.5 and 10.0±3.7 pg [Fe] per cell, respectively. Low cytotoxicity of the nanoparticles was confirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and Annexin V/7-aminoactinomycin D flow cytometry assays. For the first time, magnetic nanoparticles were applied for contrast-enhanced MRI of liver lesions induced by Opisthorchis felineus.Conclusion: The synthesized APS-modified iron oxide nanoparticles showed high efficiency as an MRI contrast agent for the evaluation of opisthorchiasis-related liver damage. Keywords: magnetic nanoparticles, alkoxysilane, magnetic resonance imaging, liver fluk