Photometry of the Stingray Nebula (V839 Ara) from 1889-2015 Across the Ionization of Its Planetary Nebula

Up until around 1980, the Stingray was an ordinary B1 post-AGB star, but then it suddenly sprouted bright emission lines like in a planetary nebula (PN), and soon after this the Hubble Space Telescope (HST) discovered a small PN around the star, so apparently we have caught a star in the act of ionizing a PN. We report here on a well-sampled light curve from 1889 to 2015, with unique coverage of the prior century plus the entire duration of the PN formation plus three decades of its aftermath. Surprisingly, the star anticipated the 1980's ionization event by declining from B=10.30 in 1889 to B=10.76 in 1980. Starting in 1980, the central star faded fast, at a rate of 0.20 mag/year, reaching B=14.64 in 1996. This fast fading is apparently caused by the central star shrinking in size. From 1994-2015, the V-band light curve is almost entirely from the flux of two bright [OIII] emission lines from the unresolved nebula, and it shows a consistent decline at a rate of 0.090 mag/year. This steady fading (also seen in the radio and infrared) has a time scale equal to that expected for ordinary recombination within the nebula, immediately after a short-duration ionizing event in the 1980s. We are providing the first direct measure of the rapidly changing luminosity of the central star on both sides of a presumed thermal pulse in 1980, with this providing a strong and critical set of constraints, and these are found to sharply disagree with theoretical models of PN evolution.Comment: ApJ accepted, 54 pages, 4 figures, one long data tabl

Sex-role orientation and response to cognitive stressors

The present study was aimed at investigating the relationship between sex-role orientation, as defined by the BSRI, and heart-rate response to stress. After being administered both the BSRI and JAS, 35 female undergraduate volunteers were randomly assigned to one of two orders of presentation, of moderately stressful verbal and spatial tasks. Heart-rate was measured throughout the experimental situation, and subjects rated each task for perceived pleasantness. A significant (p=.032) interaction was found between masculinity and femininity, with the androgynous and undifferentiated groups showing lower heart-rate increases to both tasks. Neither the BSRI nor the JAS Type A scales were found to be significantly related with subjects' performance on either task, although a trend did emerge with higher masculinity scores being linked with somewhat better performance. Furthermore, masculinity was significantly associated with reports of greater perceived pleasantness for both tasks. While the Type A variable was positively correlated with masculinity, and negatively correlated with femininity, it did not account for any of the above relationships

Conformal Galilean Spin-3 Gravity in 3d

We consider Galilean limit of conformal algebra for spin-2 and spin-3 fields, and study the gauge theory of these algebras. We analyze the equations of motion and obtain the spectra of the theories.Comment: 20 page

Modeling the momentum distributions of annihilating electron-positron pairs in solids

Measuring the Doppler broadening of the positron annihilation radiation or the angular correlation between the two annihilation gamma quanta reflects the momentum distribution of electrons seen by positrons in the material.Vacancy-type defects in solids localize positrons and the measured spectra are sensitive to the detailed chemical and geometric environments of the defects. However, the measured information is indirect and when using it in defect identification comparisons with theoretically predicted spectra is indispensable. In this article we present a computational scheme for calculating momentum distributions of electron-positron pairs annihilating in solids. Valence electron states and their interaction with ion cores are described using the all-electron projector augmented-wave method, and atomic orbitals are used to describe the core states. We apply our numerical scheme to selected systems and compare three different enhancement (electron-positron correlation) schemes previously used in the calculation of momentum distributions of annihilating electron-positron pairs within the density-functional theory. We show that the use of a state-dependent enhancement scheme leads to better results than a position-dependent enhancement factor in the case of ratios of Doppler spectra between different systems. Further, we demonstrate the applicability of our scheme for studying vacancy-type defects in metals and semiconductors. Especially we study the effect of forces due to a positron localized at a vacancy-type defect on the ionic relaxations.Comment: Submitted to Physical Review B on September 1 2005. Revised manuscript submitted on November 14 200

Isolamento e caracterização molecular do vírus de Influenza suína.

Projeto/Plano de Ação: 03.03.23.200

Diagnosing fouling of hollow fibre MF membranes in wastewater reclamation

Fouling in membrane filtration processes is problematic but inevitable as it occurs with the retention of contaminants that accumulate on the membrane surface. The causes of fouling are often specific, depending upon feed water constituents, the membrane, and the operation regime. Therefore, it is desirable that a thorough investigation is performed on fouled membrane elements of the affected plant. This technique is known as membrane autopsy , which identities the cause of poor membrane performance, and hence, gives the opportunity to rectify or mitigate the problem and improve future plant design. In this study, the cause of membrane fouling at a small water recycling plant using a hollow fibre micro filtration (MF) system is investigated. A membrane autopsy protocol has been developed for water recycling applications that consists of four major steps: I) tensile testing to investigate the membrane mechanical integrity, (II) direct visual inspection, III) membrane surface analysis using field-emission environmental scanning electron microscopy (FESEM) (as well as atomic force microscopy (AFM) although it is not used in this case) techiques, and IV) foulant constituent analysis. Results obtained from this study indicate that the membrane has been fouled by a mixture of colloids and organic matters, enhanced by the presence of multivalent cations. Possible measures to mitigate fouling in this particular case have also been suggested

Physics issues in simulations with dynamical overlap fermions

We discuss the impact of various improvements on simulations of dynamical overlap fermions using the Hybrid Monte Carlo algorithm. We focus on the usage of fat links and multiple pseudo-fermion fields.Comment: 14 pages, 10 figure

Abstract delta modelling

Article / Letter to editorLeiden Inst Advanced Computer Science

Thermal Dileptons from a Nonperturbative Quark-Gluon Phase

Assuming that gluon condensates are important even above the deconfining phase transition, we develop a model for the dilepton yield from a quark gluon plasma. Using a simple fire ball description of a heavy ion collision, and various estimates of the strengths of the gluon condensates, we compare our predicted dilepton yields with those observed in the CERES and HELIOS experiments at CERN. The simple model gives an adequate description of the data, and in particular it explains the observed considerable enhancement of the yield in the low mass region.Comment: 7 pages, 6 figures, reference adde