SN2014J gamma rays from the 56Ni decay chain

Context. The detection and measurement of gamma-ray lines from the decaychain of 56Ni provides unique information about the explosionin supernovae. SN2014J at 3.3 Mpc is a sufficiently-nearby supernova oftype Ia so that such measurements have been feasible with the gamma-rayspectrometer SPI on ESA's INTEGRAL gamma-ray observatory.

Aims:The 56Ni freshly produced in the supernova is understood topower the optical light curve, because it emits gamma rays upon itsradioactive decay first to 56Co and then to 56Fe.Gamma-ray lines from 56Co decay are expected to becomedirectly visible through the white dwarf material several weeks afterthe explosion, as they progressively penetrate the overlying material ofthe supernova envelope, which is diluted as it expands. The lines areexpected to be Doppler-shifted or broadened from the kinematics of the56Ni ejecta. We aim to exploit high-resolution gamma-rayspectroscopy with the SPI spectrometer on INTEGRAL toward constrainingthe 56Ni distribution and kinematics in this supernova.

Methods: We use the observations with the SPI spectrometer onINTEGRAL, together with an improved instrumental background method.

Results: We detect the two main lines from 56Co decay at847 and 1238 keV, which are significantly Doppler-broadened, and atintensities (3.65 ± 1.21) × 10-4 and (2.27± 0.69) × 10-4 ph cm-2s-1, respectively, at their brightness maximum. We measuretheir rise toward a maximum after about 60-100 days and a declinethereafter. The intensity ratio of the two lines is found to beconsistent with expectations from 56Co decay (0.62 ±0.28 at brightness maximum, the expected ratio is 0.68). We find thatthe broad lines seen in the late, gamma-ray transparent phase are notrepresentative of the early gamma-ray emission, and notice instead thatthe emission spectrum is complex and irregular until the supernova isfully transparent to gamma rays, with progressive uncovering of the bulkof 56Ni. We infer that the explosion morphology is notspherically symmetric, both in the distribution of 56Ni andin the unburnt material which occults the 56Co emission.After we compare light curves from different plausible models, theresulting 56Ni mass is determined to be 0.49 ± 0.09M⊙.

Solar coronal magnetic fields derived using seismology techniques applied to omnipresent sunspot waves

Sunspots on the surface of the Sun are the observational signatures of intense manifestations of tightly packed magnetic field lines, with near-vertical field strengths exceeding 6,000 G in extreme cases1. It is well accepted that both the plasma density and the magnitude of the magnetic field strength decrease rapidly away from the solar surface, making high-cadence coronal measurements through traditional Zeeman and Hanle effects difficult as the observational signatures are fraught with low-amplitude signals that can become swamped with instrumental noise2, 3. Magneto-hydrodynamic (MHD) techniques have previously been applied to coronal structures, with single and spatially isolated magnetic field strengths estimated as 9–55 G (refs 4,5,6,7). A drawback with previous MHD approaches is that they rely on particular wave modes alongside the detectability of harmonic overtones. Here we show, for the first time, how omnipresent magneto-acoustic waves, originating from within the underlying sunspot and propagating radially outwards, allow the spatial variation of the local coronal magnetic field to be mapped with high precision. We find coronal magnetic field strengths of 32 ± 5 G above the sunspot, which decrease rapidly to values of approximately 1 G over a lateral distance of 7,000 km, consistent with previous isolated and unresolved estimations. Our results demonstrate a new, powerful technique that harnesses the omnipresent nature of sunspot oscillations to provide magnetic field mapping capabilities close to a magnetic source in the solar corona.

Generation of cluster states in optomechanical quantum systems

We consider an optomechanical quantum system composed of a single cavity mode interacting with N mechanical resonators. We propose a scheme for generating continuous-variable graph states of arbitrary size and shape, including the so-called cluster states for universal quantum computation. The main feature of this scheme is that, differently from previous approaches, the graph states are hosted in the mechanical degrees of freedom rather than in the radiative ones. Specifically, via a 2N-tone drive, we engineer a linear Hamiltonian which is instrumental to dissipatively drive the system to the desired target state. The robustness of this scheme is assessed against finite interaction times and mechanical noise, confirming it as a valuable approach towards quantum state engineering for continuous-variable computation in a solid-state platform.

Doxorubicin induces the cleavage of Poly (ADP-ribose) polymerase, a marker of programmed cell death (apoptosis) in mouse cardiomyocytes

Cancer is one of the leading causes of death in the world. Despite this, a growing number of people are surviving the disease due to medical advancements and the development of numerous new therapies. Doxorubicin, a chemotherapeutic agent, is a widely-used and successful first-line anti-tumour treatment. However, the established toxic and deleterious effects of the drug on the cardiovascular system confer increased risk of congestive heart failure, thereby necessitating the use of reduced doxorubicin doses. In order to investigate how these events are initiated, mouse cardiomyocytes (HL-1) were treated in vitro with varying concentrations of doxorubicin (0.5-4.0 µmol/L). Following treatment (24h), a marked level of cell death was observed in comparison to untreated cardiomyocytes; the level of death appeared to correlate with the concentration of the drug used. Western blotting revealed the cleavage of full length Poly (ADP-ribose) polymerase (PARP) into 89 and 24kDa fragments, a process which is instrumental in triggering programmed cell death/apoptosis. Importantly, results suggested that this event may be independent of caspase 3 cleavage and thus activation. A number of previous studies have reported a functional role for both Mitofusin-2 (Mfn2) and NADPH oxidase 2 (Nox2) in the cardiotoxic response. Given that PARP cleavage is a validated indicator of cellular apoptosis, these results clearly indicate that this marker could be used in future studies when determining if depletion of the above proteins would cause a reduction in or eradicate the pro-apoptotic action of this agent on cardiomyocytes. Such investigations may lead to significant developments in ensuring that doxorubicin can achieve its full therapeutic anti-tumour potential without causing the subsequent deleterious effects on the cardiovascular system.