Sub-arcsecond Morphology of Planetary Nebulae

Planetary nebulae (PNe) can be roughly categorized into several broad morphological classes. The high quality images of PNe acquired in recent years, however, have revealed a wealth of fine structures that preclude simplistic models for their formation. Here we present narrow-band, sub-arcsecond images of a sample of relatively large PNe that illustrate the complexity and variety of small-scale structures. This is especially true for bipolar PNe, for which the images reveal multi-polar ejections and, in some cases, suggest turbulent gas motions. Our images also reveal the presence or signs of jet-like outflows in several objects in which this kind of component has not been previously reported.Comment: 7 pages, 7 figures, Accepted for publication in PAS

An updated catalog of OH-maser-emitting planetary nebulae

Aims. We studied the characteristics of planetary nebulae (PNe) that show both OH maser and radio continuum emission (hereafter OHPNe). These have been proposed to be very young PNe, and therefore, they could be key objects for understanding the formation and evolution of PNe. Methods. We consulted the literature searching for interferometric observations of radio continuum and OH masers toward evolved stars, including the information from several surveys. We also processed radio continuum and OH maser observations toward PNe in the Very Large Array data archive. The high positional accuracy provided by interferometric observations allow us to confirm or reject the association between OH maser and radio continuum emission. Results. We found a total of six PNe that present both OH maser and radio continuum emissions, as confirmed with radio interferometric observations. These are bona fide OHPNe. The confirmed OHPNe present a bipolar morphology in resolved images of their ionized emission at different wavelengths, suggesting that the OH maser emission in PNe is related to nonspherical mass-loss phenomena. The OH maser spectra in PNe present a clear asymmetry, tending to show blueshifted emission with respect to the systemic velocity. Their infrared colors suggest that most of these objects are very young PNe. OHPNe do not form a homogeneous group, and seem to represent a variety of different evolutionary stages. We suggest that OH masers pumped in the AGB phase may disappear during the post-AGB phase, but reappear once the source becomes a PN and its radio continuum emission is amplified by the OH molecules. Therefore, OH maser emission could last significantly longer than the previously assumed 1000 yr after the end of the AGB phase. This maser lifetime may be longer in PNe with more massive central stars, which ionize a larger amount of gas in the envelope.Comment: 16 pages, 5 figures, 4 tables. Accepted for publication by Astronomy & Astrophysic

On-off intermittency and amplitude-phase synchronization in Keplerian shear flows

We study the development of coherent structures in local simulations of the magnetorotational instability in accretion discs in regimes of on-off intermittency. In a previous paper [Chian et al., Phys. Rev. Lett. 104, 254102 (2010)], we have shown that the laminar and bursty states due to the on-off spatiotemporal intermittency in a one-dimensional model of nonlinear waves correspond, respectively, to nonattracting coherent structures with higher and lower degrees of amplitude-phase synchronization. In this paper we extend these results to a three-dimensional model of magnetized Keplerian shear flows. Keeping the kinetic Reynolds number and the magnetic Prandtl number fixed, we investigate two different intermittent regimes by varying the plasma beta parameter. The first regime is characterized by turbulent patterns interrupted by the recurrent emergence of a large-scale coherent structure known as two-channel flow, where the state of the system can be described by a single Fourier mode. The second regime is dominated by the turbulence with sporadic emergence of coherent structures with shapes that are reminiscent of a perturbed channel flow. By computing the Fourier power and phase spectral entropies in three-dimensions, we show that the large-scale coherent structures are characterized by a high degree of amplitude-phase synchronization.Comment: 17 pages, 10 figure

Emergent SU(3) symmetry in random spin-1 chains

We show that generic SU(2)-invariant random spin-1 chains have phases with an emergent SU(3) symmetry. We map out the full zero-temperature phase diagram and identify two different phases: (i) a conventional random singlet phase (RSP) of strongly bound spin pairs (SU(3) "mesons") and (ii) an unconventional RSP of bound SU(3) "baryons", which are formed, in the great majority, by spin trios located at random positions. The emergent SU(3) symmetry dictates that susceptibilities and correlation functions of both dipolar and quadrupolar spin operators have the same asymptotic behavior.Comment: 5 pages plus 3-page Supplemental Material, 5 figures; published versio

The importance of community development for health and well-being

Public health - Economic aspects

Impact of acute and long-term exposure to oxybenzone on the Caenorhabditis elegans life history

UV-filters are the active ingredients providing weatherproofing to industrial products and UV-light protection in personal care products such as sun-tan lotions. Sun-tan lotions products are commonly recommended to protect the skin from the sun’s damaging rays however their increasing prevalence in drinking water and aquatic environments has raised concern regarding their effect on both human and environmental health. The common UV-filter Oxybenzone (BP-3) has been highlighted as a compound of particular concern due to its high prevalence, its known toxicity in aquatic species and its ability to accumulate in the active sludge of waste-water treatment plants. Here, we investigate for the first time the effect of BP-3 on the fecundity and growth of the terrestrial nematode Caenorhabditis elegans and develop a novel method of modelling the UV-filter pollution associated with the use of UV-filter contaminated active sludge as fertilizer. Our results show that four hour BP-3 exposure did not affect reproductive health at environmentally relevant concentrations (experimental concentrations of 50, 100, 250 and 500 μg/L) however, two of three replicates demonstrated a significant effect of BP-3 (experimental concentrations of 500, 1000, 1500, 2000 μg/L) on total C. elegans fecundity. One replicate also demonstrated that nematodes acutely exposed to 500 μg/L of BP-3 were significantly larger than those measured before the experiment, potentially suggesting an effect on the nematodes ability to control osmolarity. It was found that BP-3 did not influence the growth of C.elegans, which contradicts previous research. This highlights the need for further investigation into BP-3 toxicity. Finally, it was found that in one of the replicates, the nematodes exposed to E. coli contaminated with 1500 μg/L BP-3 were significantly smaller than those exposed to E. coli contaminated with 1000 μg/L BP-3,suggesting the need for further investigation into the potential environmental risks associated with UV-filter pollution originating from active sludge. In conclusion the research conducted in this project provides a novel insight into BP-3 toxicity and the development of a universal toxicity model, which could provide reasoning for the implementation of restrictions on dangerous UV-filters both in localised areas but also internationally