VISIR-VLT Images of the Water Maser Emitting Planetary Nebula K 3-35

K3-35 is an extremely young bipolar planetary nebula that contains a precessing bipolar jet and a small (radius 80 AU) water maser equatorial ring. We have obtained VISIR- VLT images of K 3-35 in the PAH1 ({\lambda}=8.6 {\mu}m), [S iv] ({\lambda}=10.6 {\mu}m), and SiC ({\lambda}=11.85 {\mu}m) filters to analize the mid-IR morphology and the temperature structure of its dust emission. The images show the innermost nebular regions undetected at optical wavelegths and the precessing bipolar jets. The temperature map shows variations in the temperature in the equatorial zone and in regions associated to its jets.Comment: 2 pages, 2 figures, 283 IAU Symp. Planetary Nebulae an Eye to the Futur

VISIR-VLT high resolution study of the extended emission of four obscured post-AGB candidates

The onset of the asymmetry of planetary nebulae (PNe) is expected to occur during the late Asymptotic Giant Branch (AGB) and early post-AGB phases of low- and intermediate-mass stars. Among all post-AGB objects, the most heavily obscured ones might have escaped the selection criteria of previous studies detecting extreme axysimmetric structures in young PNe. Since the most heavily obscured post-AGB sources can be expected to descend from the most massive PN progenitors, these should exhibit clear asymmetric morphologies. We have obtained VISIR-VLT mid-IR images of four heavily obscured post-AGB objects barely resolved in previous Spitzer IRAC observations to analyze their morphology and physical conditions across the mid-IR. The VISIR-VLT images have been deconvolved, flux calibrated, and used to construct RGB composite pictures as well as color and optical depth maps that allow us to study the morphology and physical properties of the extended emission of these sources. We have detected extended emission from the four objects in our sample and resolved it into several structural components that are greatly enhanced in the temperature and optical depth maps. They reveal the presence of asymmetry in three young PNe (IRAS 15534-5422, IRAS 17009-4154, and IRAS 18454+0001), where the asymmetries can be associated with dusty torii and slightly bipolar outflows. The fourth source (IRAS 18229-1127), a possible post-AGB star, is better described as a rhomboidal detached shell. The heavily obscured sources in our sample do not show extreme axisymmetric morphologies. This is at odds with the expectation of highly asymmetrical morphologies in post-AGB sources descending from massive PN progenitors. The sources presented in this paper may be sampling critical early phases in the evolution of massive PN progenitors, before extreme asymmetries develop.Comment: 9 pages, 4 figure

The Formation of Alluvial Platinum-Group Minerals: Present Knowledge and the Way Ahead

The weathering of platinum-group element (PGE) deposits presents unusual problems, especially in the very active environment of lateritic weathering under tropical conditions. There is clear evidence of the destruction of platinum-group minerals (PGM) to form PGE oxides, or fine intergrowths between relict PGM and iron oxides or hydroxides, as an intermediate stage during weathering. The PGE released by weathering are transported in solution with the more soluble Pd species remaining in solution and travelling further than the less soluble Pt species. The presence of PGM in the laterite differing in mineralogy, mineral assemblage and size from those in the primary rock is difficult to explain, especially when they show secondary textures. Differing interpretations have created controversy. Are alluvial PGM derived unaltered from the primary rock where they are rare and, therefore, not encountered by standard petrographic examination? Is it possible that they could have developed in the laterite by some process that we do not yet fully understand? Some favourable genetic conditions have been outlined and debated. For more than 100 years authors have reported secondary ore textures and recently proposed a biogenic origin. Frank Reith and his co-workers provided evidence of a process involving metallophillic bacteria which, for the first time, demonstrates PGM growth in the laboratory under supergene conditions. Their work shows that a mechanism for supergene growth ('neoformation') can occur, which offers a new field of study of the appropriate Eh, pH, f(O2) conditions and organic and bacterial reactions that could permit supergene growth.Funding from Golden Prospect Mining Company in the UK, and the assistance of the late Prof. H.M. Prichard and Dr M.T. Jackson of Cardiff University. SSB received generous funding from the Department of Education, Universities and Research of the Basque Government (Refs. BFI-2011-254, IT762-13)

Serial Dependence in Visual Variance

The recent history of perceptual experience has been shown to influence subsequent perception. Classically, this dependence on perceptual history has been examined in sensory adaptation paradigms, wherein prolonged exposure to a particular stimulus (e.g. a vertically oriented grating) produces changes in perception of subsequently presented stimuli (e.g. the tilt aftereffect). More recently, several studies have investigated the influence of shorter perceptual exposure with effects, referred to as serial dependence, being described for a variety of low and high-level perceptual dimensions. In this study, we examined serial dependence in the processing of dispersion statistics, namely variance - a key descriptor of the environment and indicative of the precision and reliability of ensemble representations. We found two opposite serial dependencies operating at different timescales, and likely originating at different processing levels: A positive, Bayesian-like bias was driven by the most recent exposures, dependent on feature-specific decision-making and appearing only when high confidence was placed in that decision; and a longer-lasting negative bias - akin to an adaptation after-effect - becoming manifest as the positive bias declined. Both effects were independent of spatial presentation location and the similarity of other close traits, such as mean direction of the visual variance stimulus. These findings suggest that visual variance processing occurs in high-level areas, but is also subject to a combination of multi-level mechanisms balancing perceptual stability and sensitivity, as with many different perceptual dimensions.</p

Young learners' bilingual status and cognitive development in foreign language aptitude testing

Young learners' L1s preference, cognitive development and bilingual status might influence their performance on language aptitude tests, particularly if these are language-dependent. The objective of this study was to test the validity, reliability and consistency across populations of two such tests: the Modern Language Aptitude Test-Elementary in Catalan (MLAT-EC) and in Spanish (MLAT-ES). 629 bilingual students from grades 3 to 7 took the MLAT-ES and the MLAT-EC for test comparison in a counterbalanced order. The results show that their performance on both tests presented hardly any significant differences considering students' L1 preference (Catalan, Spanish or no preference). In addition, these bilingual examinees outperformed the predominantly monolingual samples in the MLAT-ES norming study. The same score patterns related to young learner cognitive development stages were found across test versions. These results reinforce the confidence in the validity of the MLAT-E adaptations and support the hypothesis that bilingualism results in greater aptitude

Sensory Mechanisms of Perceptual Uniformity

BACKGROUND AND AIMS: Visual experience appears rich in detail despite the poor performance of the vast majority of the visual field, as a result of the integration of coarse peripheral signals with the information of the comparatively tiny fovea. We examined the mechanisms of this integration by employing the uniformity illusion, in which a pattern with different properties in fovea and periphery uniformly takes the appearance of the fovea. We developed an adaptation paradigm to investigate whether the direction of an after-effect in the visual periphery followed the local, physical stimulation or the perception that arose under the Uniformity Illusion. We employed two different perceptual dimensions (orientation and spatial density) to investigate the extent to which the uniformity illusion is associated with changes in sensory encoding. RESULTS AND CONCLUSIONS: Experiments performed on two visual domains indicate that the uniformity illusion is not associated with a change in the sensory encoding on a local basis. Specifically, in our orientation experiments, the (V1-based) tilt after-effect only ever followed the local, physically presented orientation rather than the global orientation perceived under the illusion of uniformity. This was not due to insufficient exposure to the global pattern to produce an after-effect as presentation of physical uniformity for the same durations as participant reports of the illusion did produce an after-effect to the global orientation. Results on spatial-density based experiments showed an intermediate level of adaptation between (physical) low and high density, which could be consistent with an adaptation exerted by the illusory pattern. Thus, we could not rule out that the Uniformity Illusion might directly modify more abstract dimensions (such as numerosity, akin to our formalization of spatial density). However, the time invariance of the effect makes alternative explanations more likely and therefore, suggests that the uniformity illusion arises from high-level perceptual processes

Water fragmentation by bare and dressed light ions with MeV energies: Fragment-ion-energy and time-of-flight distributions

The energy and time-of-flight distributions of water ionic fragments produced by impact of fast atoms and bare and dressed ions; namely, H+, Li0-3+, C1+, and C2+ are reported in this work. Fragment species as a function of emission energy and time-of-flight were recorded by using an electrostatic spectrometer and a time-of-flight mass spectrometer, respectively. An improved Coulomb explosion model coupled to a classical trajectory Monte Carlo (CTMC) simulation gave the energy centroids of the fragments for the dissociation channels resulting from the removal of two to five electrons from the water molecule. For the energy distribution ranging up to 50 eV, both the experiment and model reveal an isotropic production of multiple charged oxygen ions, as well as hydrogen ions. From the ion energy distribution, relative yields of the dissociation resulting from multiple ionization were obtained as a function of the charge state, as well as for several projectile energies. Multiple-ionization yields with charge state up to 4+, were extracted from the measurements of the time-of-flight spectra, focused on the production of single and multiple charged oxygen ions. The measurements were compared to ion-water collision experiments investigated at the keV energy range available in the literature, revealing differences and similarities in the fragment-ion energy distribution.Fil: Wolff, W.. Universidade Federal do Rio de Janeiro; BrasilFil: Luna, H.. Universidade Federal do Rio de Janeiro; BrasilFil: Schuch, R.. Alba Nova University Center; SueciaFil: Cariatore, Nelson Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Otranto, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Turco, Federico. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Fregenal, Daniel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Bernardi, Guillermo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Suárez, S.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin

Effect of antimony on the eutectic reaction of heavy section spheroidal graphite castings

There is a strong demand for heavy section castings made of spheroidal graphite with a fully ferritic matrix, e.g. for manufacturing hubs for windmills. Such castings with slow solidification process are prone to graphite degeneration that leads to a dramatic decrease of the mechanical properties of the cast parts. Chunky graphite is certainly the most difficult case of graphite degeneracy, though it has long been known that the limited and controlled addition of antimony may help eliminate it. The drawback of this remedy is that too large Sb additions lead to other forms of degenerate graphite, and also that antimony is a pearlite promoter. As part of an investigation aimed at mastering low level additions to cast iron melts before casting, solidification of large blocks with or without Sb added was followed by thermal analysis. Comparison of the cooling curves and of the microstructures of these different castings gives suggestions to understand the controlling nucleation and growth mechanisms for chunky graphite cells

Semiclassical time--dependent propagation in three dimensions: How accurate is it for a Coulomb potential?

A unified semiclassical time propagator is used to calculate the semiclassical time-correlation function in three cartesian dimensions for a particle moving in an attractive Coulomb potential. It is demonstrated that under these conditions the singularity of the potential does not cause any difficulties and the Coulomb interaction can be treated as any other non-singular potential. Moreover, by virtue of our three-dimensional calculation, we can explain the discrepancies between previous semiclassical and quantum results obtained for the one-dimensional radial Coulomb problem.Comment: 8 pages, 4 figures (EPS

Slender Ca II H fibrils mapping magnetic fields in the low solar chromosphere

S. Jafarzadeh et. al.©2017 The American Astronomical Society. All rights reserved.A dense forest of slender bright fibrils near a small solar active region is seen in high-quality narrowband Ca ii H images from the SuFI instrument onboard the Sunrise balloon-borne solar observatory. The orientation of these slender Ca ii H fibrils (SCF) overlaps with the magnetic field configuration in the low solar chromosphere derived by magnetostatic extrapolation of the photospheric field observed with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are qualitatively aligned with small-scale loops computed from a novel inversion approach based on best-fit numerical MHD simulation. Such loops are organized in canopy-like arches over quiet areas that differ in height depending on the field strength near their roots.The German contribution to Sunrise and its reflight was funded by the Max Planck Foundation, the Strategic Innovations Fund of the President of the Max Planck Society (MPG), DLR, and private donations by supporting members of the Max Planck Society, which is gratefully acknowledged. The Spanish contribution was funded by the Ministerio de Economía y Competitividad under Projects ESP2013-47349-C6 and ESP2014-56169-C6, partially using European FEDER funds. The HAO contribution was partly funded through NASA grant number NNX13AE95G. This work was partly supported by the BK21 plus program through the National Research Foundation (NRF) funded by the Ministry of Education of Korea. S.J. receives support from the Research Council of Norway. T.W. acknowledges support by DFG-grant WI 3211/4-1. M.S. acknowledges support from the European Research Council under the European Union's Seventh Framework Programme / ERC Grant agreement nr. 291058.Peer reviewe