To determine whether a synthetic ultrasonographic (US) contrast agent can be used to differentiate coagulation necrosis from untreated tumor immediately after radio-frequency ablative therapy.
VX2 ...(adenocarcinoma) tumors (0.8-1.5-cm diameter) were implanted into 12 rabbits. Gray-scale and color Doppler US were performed with or without intravenous injection of a US contrast agent composed of poly-lactide-co-glycolic acid polymeric (PLGA) microspheres (2-micron diameter) filled with perfluorocarbon gas. Radio frequency was applied to each nodule for 6 minutes at 127 mA +/- 33 (mean +/- SD) (tip temperature, 92 degrees C +/- 2). Repeat US with a second dose of the contrast agent was performed immediately after ablation. In four animals, a third dose was administered 30-120 minutes after ablation. Radiologic-histopathologic correlation was performed and included in vivo staining and studies of mitochondrial function.
Intense contrast agent enhancement was seen throughout the tumor prior to ablation. At gray-scale US, ablation produced hyperechoic foci, which were within 1 mm of the foci identified at histopathologic examination in seven of 12 animals (58%). After the administration of contrast material, foci devoid of previously visualized enhancement, which measured 7.3-15.0 mm, were identified. These were within 1 mm of the size of the foci identified at histopathologic examination in 11 of 12 animals (92%, P < .01). In two animals, enhancement depicted viable tumor, which appeared hyperechoic, on nonenhanced images. On delayed images, hyperechoic areas decreased in size, whereas the nonenhanced region remained unchanged.
A PLGA microspherical US contrast agent enabled the immediate detection of coagulation necrosis as a region devoid of contrast enhancement after radio-frequency ablation in rabbit hepatic tumors. Therefore, this agent could provide real-time guidance during complex ablative procedures and may provide an efficient technique for postprocedural assessment.
We present some results of an ongoing study of the long-term spectroscopic variations of AG Dra, a prototypical eruptive symbiotic system. We discuss the effects of the environment and orbital ...modulation in this system and some of the physical processes revealed by a comparison with the nova outburst of the symbiotic-like recurrent nova V407 Cyg 2010.
High-energy gamma-ray emission is theoretically expected to arise in tight binary star systems (with high mass loss and high-velocity winds), although the evidence of this relationship has proven to ...be elusive so far. Here we present the first bounds on this putative emission from isolated Wolf-Rayet (WR) star binaries, WR 147 and WR 146, obtained from observations with the MAGIC telescope. In the unification scheme of Seyfert galaxies, a dusty torus blocks the continuum source and broad-line region in Seyfert 2 galaxies. However it is not clear whether or not and to what extent the torus affects the narrow-line spectra. In this Letter, we show that Seyfert 1 and Seyfert 2 galaxies have different distributions on the O iii/H beta versus N ii/H alpha diagram (BPT diagram) for narrow lines. Seyfert 2 galaxies display a clear left boundary on the BPT diagram and only 7.3% of them lie on the left. By contrast, Seyfert 1 galaxies do not show such a cutoff and 33.0% of them stand on the left side of the boundary. Among Seyfert 1 galaxies, the distribution varies with the extinction to broad lines. As the extinction increases, the distribution on BPT diagram moves to larger N ii/H alpha values. We interpret this as evidence for the obscuration of an inner dense narrow-line region by the dusty torus. We also demonstrate that the O iii and broad-line luminosity correlation depends on the extinction of broad lines in the way that high-extinction objects have lower uncorrected O iii luminosities, suggesting that O iii is partially obscured in these objects. Therefore, using O iii as an indicator for the nuclear luminosity will systematically underestimate the nuclear luminosity of Seyfert 2 galaxies.
The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ...ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions.
Context. AG Dra is one of a small group of low metallicity S-type symbiotic binaries with K-type giants that undergoes occasional short-term outbursts of unknown origin. Aims. Our aim is to study the ...behavior of the white dwarf during an outburst using the optical Raman lines and other emission features in the red giant wind. The goal is to determine changes in the envelope and the wind of the gainer in this system during a major outburst event and to study the coupling between the UV and optical during a major outburst. Methods. Using medium and high resolution groundbased optical spectra and comparisons with archival FUSE and HST/STIS spectra, we study the evolution of the Raman O VI features and the Balmer, He I, and He II lines during the outburst from 2006 Sep. through 2007 May and include more recent observations (2009) to study the subsequent evolution of the source. Results. The O VI Raman features disappeared completely at the peak of the major outburst and the subsequent variation differs substantially from that reported during the previous decade. The He I and He II lines, and the Balmer lines, vary in phase with the Raman features but there is a double-valuedness to the He I 6678, 7065 relative to the O VI Raman 6825 Å variations in the period between 2006-2008 that has not been previously reported. Conclusions. The variations in the Raman feature ratio through the outburst interval are consistent with the disappearance of the O VI FUV resonance wind lines from the white dwarf and of the surrounding O+5 ionized region within the red giant wind provoked by the expansion and cooling of the white dwarf photosphere.
We present results of the multiwavelength campaign on the TeV blazar Mkn 501 performed in 2006 July, including MAGIC for the very-high-energy (VHE) Delta *g-ray band and Suzaku for the X-ray band. A ...VHE Delta *g-ray signal was clearly detected with an average flux above 200 GeV of ~20% of the Crab Nebula flux, which indicates a low state of source activity in this energy range. No significant variability has been found during the campaign. The VHE Delta *g-ray spectrum can be described by a simple power law from 80 GeV to 2 TeV with a photon index of 2.8 +/- 0.1, which corresponds to one of the steepest photon indices observed in this energy range so far for this object. The X-ray spectrum covers a wide range from 0.6 to 40 keV, and is well described by a broken power law, with photon indices of 2.257 +/- 0.004 and 2.420 +/- 0.012 below and above the break energy of 3.24+0.13 -0.12 keV. No apparent high-energy cut-off is seen above the break energy. Although an increase of the flux of about 50% is observed in the X-ray band within the observation, the data indicate a consistently low state of activity for this source. Time-resolved spectra show an evidence for spectral hardening with a flux level. A homogeneous one-zone synchrotron self-Compton (SSC) model can adequately describe the spectral energy distribution (SED) from the X-ray to the VHE Delta *g-ray bands with a magnetic field intensity B = 0.313 G and a Doppler beaming factor Delta *d = 20, which are similar to the values in the past multiwavelength campaigns in high states. Based on our SSC parameters derived for the low state, we are able to reproduce the SED of the high state by just changing the Lorentz factor of the electrons corresponding to the break energy in the primary electron spectrum. This suggests that the variation of the injected electron population in the jet is responsible for the observed low-high state variation of the SED.
With a growing number of children living in kinship foster care, it is important to understand how youths are faring in kinship care compared to youths in non-kinship care. In the present study, we ...first evaluate teacher ratings of problem behaviors exhibited in school by youths in kinship and non-kinship foster care. We then examine whether correspondences between parent and teacher ratings of problem behaviors across home and school settings differ by kinship status. The youths in the study represent an ethnically diverse sample (N = 185), with significantly more children of color in kinship placements. Across the majority of problem behavior scales on the Teacher's Report Form (TRF: Achenbach, 1991), teacher perceptions of youth behavior did not differ significantly according to kinship or non-kinship care placement. Furthermore, the youths in this study had elevated scores relative to general population norms on only a few TRF problem behavior scales. A sub-sample (N = 122) with foster parent assessments on the Child Behavior Checklist (CBCL: Achenbach, 1991) permitted comparison of perceptions of youth behavior across the home and school settings for youths in kinship and non-kinship placements. Correlations between the TRF and CBCL composite scale scores (internalizing, externalizing, and total problem behaviors) indicated slightly higher agreement between teacher and foster parent ratings for kinship placements. The non-kinship foster parents reported higher levels of problem behavior at home relative to school. The paper interprets these results and suggests implications for practice and future research directions.
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma. Since autumn 2009 both telescopes have been working together in stereoscopic mode, ...providing a significant improvement with respect to the previous single-telescope observations. We use observations of the Crab Nebula taken at low zenith angles to assess the performance of the MAGIC stereo system. The trigger threshold of the MAGIC telescopes is 50−60GeV. Advanced stereo analysis techniques allow MAGIC to achieve a sensitivity as good as (0.76±0.03)% of the Crab Nebula flux in 50h of observations above 290GeV. The angular resolution at those energies is better than ∼0.07°. We also perform a detailed study of possible systematic effects which may influence the analysis of the data taken with the MAGIC telescopes.
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