The nature of the low-frequency emission of M51: First observations of a nearby galaxy with LOFAR

The grand-design spiral galaxy M51 was observed with the LOFAR High Frequency Antennas (HBA) and imaged in total intensity and polarisation. This observation covered the frequencies between 115 MHz and 175 MHz. We produced an image of total emission of M51 at the mean frequency of 151 MHz with 20 arcsec resolution and 0.3 mJy rms noise, which is the most sensitive image of a galaxy at frequencies below 300 MHz so far. The integrated spectrum of total radio emission is described well by a power law, while flat spectral indices in the central region indicate thermal absorption. We observe that the disk extends out to 16 kpc and see a break in the radial profile near the optical radius of the disk. Our main results, the scale lengths of the inner and outer disks at 151 MHz and 1.4 GHz, arm--interarm contrast, and the break scales of the radio--far-infrared correlations, can be explained consistently by CRE diffusion, leading to a longer propagation length of CRE of lower energy. The distribution of CRE sources drops sharply at about 10 kpc radius, where the star formation rate also decreases sharply. We find evidence that thermal absorption is primarily caused by HII regions. The non-detection of polarisation from M51 at 151 MHz is consistent with the estimates of Faraday depolarisation. Future searches for polarised emission in this frequency range should concentrate on regions with low star formation rates.Comment: 20 pages, 18 figures, accepted for publication in A&

Transannular patching is a valid alternative for tetralogy of Fallot and complete atrioventricular septal defect repair

Objective: We report our experience with repair of tetralogy of Fallot associated with complete atrioventricular septal defect, addressing in particular the need for a pulmonary valve in the right ventricular outflow tract. Methods: Between 1992 and 2006, 33 children with tetralogy of Fallot and complete atrioventricular septal defect were admitted; 26 had Down’s syndrome (79%). Thirty-two children had complete repair (18 primary, 14 staged); of the 15 who received initial palliation, 1 died before complete repair. Right ventricular outflow tract obstruction was relieved by transannular patch in 14 cases (42%), infundibular patch with preservation of the pulmonary valve in 7 (21%), and right ventricle–to–pulmonary artery conduit in 11 (33%). Results: There were no hospital deaths. Actuarial survival was 96% 3.9% at 5 years and 85.9 1.1% at 10 years. Multivariate analysis showed that type of relief of right ventricular outflow tract obstruction did not influence survival (P ¼ .16), nor did the choice to use a valved conduit (P ¼ .82). Primary correction (P ¼ .05) and lower weight at repair (P ¼ .05) were associated with higher probability of survival. Mean follow-up was 69.3 5.9 months (range 0.2–282 months). There were 2 late deaths. Overall freedom from reoperation was 69% at 5 years and 38%at 10 years. Right ventricular outflow tract reconstruction without use of a valved conduit allowed a significantly higher freedom from reinterventions (P<.05). Conclusions: Tetralogy of Fallot associated with complete atrioventricular septal defect can be corrected at low risk with favorable intermediate survival. Use of right ventricle–to–pulmonary artery conduit can be avoided in two thirds of patients with no impact on survival, possibly improving overall freedom from reintervention

Transannular patching is a valid alternative for tetralogy of Fallot and complete atrioventricular septal defect repair

Objective: We report our experience with repair of tetralogy of Fallot associated with complete atrioventricular septal defect, addressing in particular the need for a pulmonary valve in the right ventricular outflow tract. Methods: Between 1992 and 2006, 33 children with tetralogy of Fallot and complete atrioventricular septal defect were admitted; 26 had Down’s syndrome (79%). Thirty-two children had complete repair (18 primary, 14 staged); of the 15 who received initial palliation, 1 died before complete repair. Right ventricular outflow tract obstruction was relieved by transannular patch in 14 cases (42%), infundibular patch with preservation of the pulmonary valve in 7 (21%), and right ventricle–to–pulmonary artery conduit in 11 (33%). Results: There were no hospital deaths. Actuarial survival was 96% 3.9% at 5 years and 85.9 1.1% at 10 years. Multivariate analysis showed that type of relief of right ventricular outflow tract obstruction did not influence survival (P ¼ .16), nor did the choice to use a valved conduit (P ¼ .82). Primary correction (P ¼ .05) and lower weight at repair (P ¼ .05) were associated with higher probability of survival. Mean follow-up was 69.3 5.9 months (range 0.2–282 months). There were 2 late deaths. Overall freedom from reoperation was 69% at 5 years and 38%at 10 years. Right ventricular outflow tract reconstruction without use of a valved conduit allowed a significantly higher freedom from reinterventions (P<.05). Conclusions: Tetralogy of Fallot associated with complete atrioventricular septal defect can be corrected at low risk with favorable intermediate survival. Use of right ventricle–to–pulmonary artery conduit can be avoided in two thirds of patients with no impact on survival, possibly improving overall freedom from reintervention

Metastates in mean-field models with random external fields generated by Markov chains

We extend the construction by Kuelske and Iacobelli of metastates in finite-state mean-field models in independent disorder to situations where the local disorder terms are are a sample of an external ergodic Markov chain in equilibrium. We show that for non-degenerate Markov chains, the structure of the theorems is analogous to the case of i.i.d. variables when the limiting weights in the metastate are expressed with the aid of a CLT for the occupation time measure of the chain. As a new phenomenon we also show in a Potts example that, for a degenerate non-reversible chain this CLT approximation is not enough and the metastate can have less symmetry than the symmetry of the interaction and a Gaussian approximation of disorder fluctuations would suggest.Comment: 20 pages, 2 figure

Pharmacogenetic analysis of liver toxicity after busulfan/cyclophosphamide-based allogeneic hematopoietic stem cell transplantation

Unlabelled: THE AIM of this study was to evaluate the impact of genomic polymorphisms of methylene-tetrahydrofolate-reductase (MTHFR-C677T, MTHFR-A1298C) and various glutathione S-transferases (GSTP1-Ilel05Val, GSTA1*a/b, GSTM1, GSTT1) on the occurrence of liver toxicity in patients receiving allogeneic hematopoietic stem cell transplantation (HSCT). Patients and methods: Eighty-four adult patients were enrolled in this retrospective study. All patients were treated with busulfan/cyclophosphamide as a conditioning regimen and received cyclosporine and short-course MTX for GvHD prophylaxis. Genotyping was performed using PCR based restriction-fragment-length-polymorphism (RFLP) techniques. Results: Multivariate analysis identified the MTHFR-A1298C polymorphism as an independent predictor for maximum levels of bilirubin (p=0.0025) and duration of hyperbilirubinaemia (p=0.013). Furthermore, there was an association between this polymorphism and the occurrence of the sinusoidal obstruction syndrome (SOS) (p=0.048). No significant associations between the MTHFR-C677T or the various GST polymorphisms and liver toxicity were observed. Conclusion: The MTHFR-A1298C polymorphism might be associated with liver toxicity in patients receiving allogeneic HSCT

A low-frequency view of mixed-morphology supernova remnant VRO 42.05.01, and its neighbourhood

Context. Mixed-morphology supernova remnants (MM SNRs) are a mysterious class of objects that display thermal X-ray emission within their radio shell. They are an older class of SNRs, and as such are profoundly affected by the environment into which they evolve. VRO 42.05.01 is a MM SNR of puzzling morphology in the direction of the Galactic anticentre. Aims. Low-frequency radio observations of supernova remnants are sensitive to synchrotron electrons accelerated in the shock front. We aim to compare the low-frequency emission to higher frequency observations to understand the environmental and shock acceleration conditions that have given rise to the observed properties of this source. Methods. We present a LOFAR High Band Antenna map centred at 143 MHz of the region of the Galactic plane centred at l = 166°, b = 3.5° at 143 MHz, with a resolution of 148" and an rms noise of 4.4 mJy bm−1. Our map is sensitive to scales as large as 6°. We compared the LOw Frequency ARay (LOFAR) observations to archival higher frequency radio, infrared, and optical data to study the emission properties of the source in different spectral regimes. We did this both for the SNR and for OA 184, an H II region within our field of view. Results. We find that the radio spectral index of VRO 42.05.01 increases at low radio frequencies; i.e. the LOFAR flux is higher than expected from the measured spectral index value at higher radio frequencies. This observed curvature in the low-frequency end of the radio spectrum occurs primarily in the brightest regions of the source, while the fainter regions present a roughly constant power-law behaviour between 143 MHz and 2695 MHz. We favour an explanation for this steepening whereby radiative shocks have high compression ratios and electrons of different energies probe different length scales across the shocks, therefore sampling regions of different compression ratios

LOFAR MSSS: Flattening low-frequency radio continuum spectra of nearby galaxies

Accepted for publication in Astronomy and AstrophysicsAims. The shape of low-frequency radio continuum spectra of normal galaxies is not well understood, the key question being the role of physical processes such as thermal absorption in shaping them. In this work we take advantage of the LOFAR Multifrequency Snapshot Sky Survey (MSSS) to investigate such spectra for a large sample of nearby star-forming galaxies. Methods. Using the measured 150 MHz flux densities from the LOFAR MSSS survey and literature flux densities at various frequencies we have obtained integrated radio spectra for 106 galaxies characterised by different morphology and star formation rate. The spectra are explained through the use of a three-dimensional model of galaxy radio emission, and radiation transfer dependent on the galaxy viewing angle and absorption processes. Results. Our galaxies' spectra are generally flatter at lower compared to higher frequencies: the median spectral index α low measured between ≈ 50 MHz and 1.5 GHz is -0.57 ± 0.01 while the high-frequency one α high, calculated between 1.3 GHz and 5 GHz, is -0.77 ± 0.03. As there is no tendency for the highly inclined galaxies to have more flattened low-frequency spectra, we argue that the observed flattening is not due to thermal absorption, contradicting the suggestion of Israel & Mahoney (1990, ApJ, 352, 30). According to our modelled radio maps for M 51-like galaxies, the free-free absorption effects can be seen only below 30 MHz and in the global spectra just below 20 MHz, while in the spectra of starburst galaxies, like M 82, the flattening due to absorption is instead visible up to higher frequencies of about 150 MHz. Starbursts are however scarce in the local Universe, in accordance with the weak spectral curvature seen in the galaxies of our sample. Locally, within galactic disks, the absorption effects are distinctly visible in M 51-like galaxies as spectral flattening around 100-200 MHz in the face-on objects, and as turnovers in the edge-on ones, while in M 82-like galaxies there are strong turnovers at frequencies above 700 MHz, regardless of viewing angle. Conclusions. Our modelling of galaxy spectra suggests that the weak spectral flattening observed in the nearby galaxies studied here results principally from synchrotron spectral curvature due to cosmic ray energy losses and propagation effects. We predict much stronger effects of thermal absorption in more distant galaxies with high star formation rates. Some influence exerted by the Milky Way's foreground on the spectra of all external galaxies is also expected at very low frequencies.Peer reviewedFinal Accepted Versio