V605 Aql: The Older Twin of Sakurai's Object

New optical spectra have been obtained with VLT/FORS2 of the final helium shell flash (FF) star, V605 Aql, which peaked in brightness in 1919. New models suggest that this star is experiencing a very late thermal pulse. The evolution to a cool luminous giant and then back to a compact hot star takes place in only a few years. V605 Aql, the central star of the Planetary Nebula (PN), A58, has evolved from T$_{eff}\sim$5000 K in 1921 to $\sim$95,000 K today. There are indications that the new FF star, Sakurai's Object (V4334 Sgr), which appeared in 1996, is evolving along a similar path. The abundances of Sakurai's Object today and V605 Aql 80 years ago mimic the hydrogen deficient R Coronae Borealis (RCB) stars with 98% He and 1% C. The new spectra show that V605 Aql has stellar abundances similar to those seen in Wolf-Rayet [WC] central stars of PNe with ~55% He, and ~40% C. The stellar spectrum of V605 Aql can be seen even though the star is not directly detected. Therefore, we may be seeing the spectrum in light scattered around the edge of a thick torus of dust seen edge-on. In the present state of evolution of V605 Aql, we may be seeing the not too distant future of Sakurai's Object.Comment: 12 pages, 1 figure, ApJ Letters in pres

Freshly ionized matter around the final Helium shell flash object V4334 Sgr (Sakurai's object)

We report on the discovery of recently ionized hydrogen-deficient gas in the immediate circumstellar environment of the final helium shell flash star V4334 Sgr (Sakurai's object). On spectra obtained with FORS2 multi-object spectroscopy we have found spatially extended (about 2") emission from [N II], [O I], [O II] and very faint Halpha and [S II]. In the [N II] (ll6548,83) lines we have identified two components located at velocities -350 +/-50 and +200 +/-50 km/s, relative to V4334 Sgr itself. The full width of the [N II] l6583 feature at zero intensity corresponds to a velocity spread of about 1500 km/s. Based on the available data it is not possible to conclusively determine the mechanism of ionization. Both photo-ionization, from a rapidly evolving central star, and shock excitation, as the result of the collision of the fast ouflows with slower circumstellar matter, could account for the observed lines. The central star is still hidden behind strong dust absorption, since only a faint highly reddened continuum is apparent in the spectra. Theory states that it will become hotter and will retrace its post-asymptotic giant branch evolution towards the planetary nebula domain. Our detection of the ionized ejecta from the very late helium shell flash marks the beginning of a new phase in this star's amazingly rapid evolution.Comment: 11 pages, 2 figures. Accepted by ApJ

The Anomalous Infrared Emission of Abell 58

We present a new model to explain the excess in mid and near infrared emission of the central, hydrogen poor dust knot in the planetary nebula (PN) Abell 58. Current models disagree with ISO measurement because they apply an average grain size and equilibrium conditions only. We investigate grain size distributions and temperature fluctuations affecting infrared emission using a new radiative transfer code and discuss in detail the conditions requiring an extension of the classical description. The peculiar infrared emission of V605 Aql, the central dust knot in Abell 58, has been modeled with our code. V605 Aql is of special interest as it is one of only three stars ever observed to move from the evolutionary track of a central PN star back to the post-AGB state.Comment: 17 pages, 4 figures; accepted and to be published in Ap

V605 Aquilae: a born again star, a nova or both?

V605 Aquilae is today widely assumed to have been the result of a final helium shell flash occurring on a single post-asymptotic giant branch star. The fact that the outbursting star is in the middle of an old planetary nebula and that the ejecta associated with the outburst is hydrogen deficient supports this diagnosis. However, the material ejected during that outburst is also extremely neon rich, suggesting that it derives from an oxygen-neon-magnesium star, as is the case in the so-called neon novae. We have therefore attempted to construct a scenario that explains all the observations of the nebula and its central star, including the ejecta abundances. We find two scenarios that have the potential to explain the observations, although neither is a perfect match. The first scenario invokes the merger of a main sequence star and a massive oxygen-neon-magnesium white dwarf. The second invokes an oxygen-neon-magnesium classical nova that takes place shortly after a final helium shell flash. The main drawback of the first scenario is the inability to determine whether the ejecta would have the observed composition and whether a merger could result in the observed hydrogen-deficient stellar abundances observed in the star today. The second scenario is based on better understood physics, but, through a population synthesis technique, we determine that its frequency of occurrence should be very low and possibly lower than what is implied by the number of observed systems. While we could not envisage a scenario that naturally explains this object, this is the second final flash star which, upon closer scrutiny, is found to have hydrogen-deficient ejecta with abnormally high neon abundances. These findings are in stark contrast with the predictions of the final helium shell flash and beg for an alternative explanation.Comment: 8 pages, 1 figures, 2 tables, accepted for MNRAS. Better title and minor corrections compared to previous versio

The Blanche Ward Story

Written interview with Blanche Ward, a Hall of Fame teacher.https://scholars.fhsu.edu/ors/1265/thumbnail.jp

Retinal function of the voltage-gated calcium channel subunit α2δ-3 / Light-dependent effects in α2δ-3 mutant and in wild type retina

The retina employs a large number of cell types that fulfill a broad spectrum of computations. It comes as no surprise that this complex network would make use of an equal diversity of molecular tools, such as voltage-gated calcium channels (VGCC). In fact, all pore-forming α1 subunits of VGCC and modulatory β and auxiliary α2δ subunits were found in the retina. Yet, little detail is known about the functional implementation of individual VGCC subunits in the retinal circuitry. My work described in part 1 focused on the retinal expression and function of one VGCC subunit, called α2δ-3, employing an α2δ-3 knockout mouse. I found transcription of all α2δ subunit genes throughout postnatal retinal development and strong expression of α2δ-3 in horizontal cells. Yet, in my patch-clamp recordings from isolated horizontal cells I did not find an impact on their somatic calcium currents, leaving a possible involvement of α2δ-3 in the horizontal cell axon-to-rod connection. Outer retina function, determined by electroretinogram, and optokinetic reflex behavior was normal in α2δ-3 knockout animals. However, I discovered changes to the retinal output in micro-electrode array recordings of ganglion cell responses. I applied a paradigm of light stimulation at different ambient luminance levels that revealed effects of the α2δ-3 knockout only in scotopic and mesopic light levels. In summary, α2δ-3 is a candidate for horizontal cell axon-specific calcium signal modulation and exerts its function in non-photopic regimes. The retina constantly adapts to features of the current visual environment, most prominently, the ambient light intensity or luminance. These adaptations are based on mechanisms throughout the retinal network. Adaption is commonly considered to keep signal processing within the dynamic range of the system as well as keep the retinal output stable across changing conditions, such as the light intensity. The results of part 1 show that different building blocks of retinal circuits - here the α2δ-3 subunit - can contribute to retinal function at distinct light level regimes. In part 2, we looked more generally at the output of the retina (responses of ganglion cells) across different levels of ambient luminance. We found that ganglion cell responses were not stable across luminance levels, neither in single ganglion cell types nor in the ganglion cell population, but that they changed their responses qualitatively. These response changes were also reflected downstream in the activity of the lateral geniculate nucleus. Furthermore, we observed that rod photoreceptors could drive visual responses of ganglion cells in photopic luminance levels, where they were commonly thought to be saturated. While experiencing initial incremental saturation upon stepping to photopic luminance, rods recovered responsiveness at all light levels tested, but the rate of recovery was faster with brighter ambient light intensity. Computational modeling suggested adaptive translocation of elements of the signal transduction cascade as potential explanations for rod signaling at high light intensities. The photopic rod activity dynamics have important implications for the interpretation of experimental data and for the question of rod photoreceptor contributions to daylight vision. In summary, while some circuitry elements associated with luminance regimes are known (e.g. rod and cone pathways), details on the underlying molecular mechanisms are scarce. My data suggests α2δ-3 as a promising candidate for a molecular determinant of light adaptation that could exert its function within horizontal cells in an axonal compartment-specific way. It will be interesting to pinpoint the exact role of α2δ- 3 in retinal light adaptation and to determine what (sub-)cellular function this protein serves in horizontal cells

Safety assessment of coagulase-negative staphylococci used in food production

Coagulase-negative staphylococci (CNS) are used in starter cultures for the production of fermented meat products due to their involvement in the development of desired red color, characteristic flavor as well as ensuring stability. But also other CNS species like S. condimenti, S. piscifermentans, S. equorum and S. succinus have a potential for future use in starter cultures. The safety of fermented food products is principally proven by long-term experience as traditional methods are considered safe based on their long history of safe use. However, for the last mentioned species long-term experience concerning sanitary harmlessness exists only with limitations. To get an insight in safety relevant properties of food associated CNS in Chapter III-V strains of the species S. carnosus, S. condimenti and S. piscifermentans (S. carnosus-group) as well as S. equorum, S. succinus and S. xylosus (S. xylosus-group) were phenotypically and partly genotypically investigated. Based on these insights in Chapter VI a DNA microarray was developed for rapid and simultaneous detection of various safety relevant properties in CNS with future use in the food production. To increase the application potential of this microarray, additionally technological relevant properties were considered in the array design. Subsequently, the designed microarray was used for the genotypic investigation of phenotypically characterized CNS concerning the presence of safety relevant properties. In Chapter III, antibiotic resistances of 330 CNS belonging to S. carnosus- and S. xylosus-group isolated from food and starter cultures were examined. Resistances to 21 antibiotics were phenotypically determined and resistance genes blaZ, lnuA and tetK were detected in strains showing phenotypic resistances to ß-lactam antibiotics, lincomycin and tetracycline. Antibiotic resistance profiles in strains of the species S. equorum, S. succinus and S. piscifermentans are described and due to the high number of investigated strains an insight regarding the occurrence of antibiotic resistances in food associated CNS is given. In Chapter IV toxin production of food associated CNS belonging to S. carnosus- and S. xylosus-group was investigated. First, 330 strains isolated from food, starter cultures and clinical isolates have been analyzed to hemolytic activity on human and sheep blood agar plates. Secondly, the ability of 35 selected strains to produce staphylococcal enterotoxins, toxic shock syndrome toxin 1 and exfoliative toxin A has been examined by immunoblot analysis. The chapter demonstrates that CNS strains present in high numbers in fermented food cannot necessarily be regarded as safe. Thus, strains used in the production of fermented food should be analyzed with respect of their toxigenic potential to avoid negative effects on human health. Chapter V is dealing with the formation of binding proteins to extracellular matrix proteins (ECM) and the production of biogenic amines (BA) by 32 CNS of S. carnosus- and S. xylosus-group. Binding capacity of CNS to the ECM fibronectin and fibrinogen was investigated by detection of fluorescent labeled cells which were added to microtiter plates coated with ECM. The formation of six important BA was examined by HPLC using growing and resting cells. By the results of this chapter the ability of food associated CNS to develop undesired properties like the formation of binding proteins to ECM and BA was demonstrated. Thus, further research is needed concerning potential risks and the importance on human health if strains with these properties are used in the production of fermented food. In Chapter VI, the design of a polynucleotide based DNA microarray as screening tool to detect genes of potential health concern and technological relevance in food associated CNS is described. The array considered 220 genes encoding for antibiotic resistances, hemolysins, toxins, amino acid decarboxylases (involved in the formation of BA), binding proteins to ECM, lipases, proteases, stress response factors, and nitrate dissimilation. Hybridization experiments were performed using genomic DNA isolated of 32 in Chapter III-V phenotypically characterized CNS allowing the detection of e.g. antibiotic resistance genes blaZ, lnuA, and tetK. Genes coding for decarboxylases as well as fibronectin and fibrinogen binding proteins were rarely correlated with the phenotype. Toxin genes could not be detected, whereas technological relevant genes like genes coding for proteases, lipases, catalase, superoxide dismutase or genes involved in dissimilatory nitrate reduction resulted in hybridization signals. The present thesis provides data concerning safety relevant properties in food associated CNS which are important for accurate safety assessment. Comparison of the results of Chapter III-V with them of Chapter VI showed that antibiotic resistances, formation of toxins and binding proteins to ECM are more present in strains of S. xylosus- than in S. carnosus-group. In context with safety assessment of food associated CNS, the designed microarray can be used as screening tool for the detection of safety relevant combined with technologically important properties (nitrate dissimilation, control of oxidative damage by catalase, flavor formation by proteases and lipases). Summarizing, the array is able to make a contribution in enhancing the selection criteria of CNS used as starter organisms in respect to food safety as well as technologically relevant properties.Koagulase negative Staphylokokken (KNS) werden in Starterkulturen für die Herstellung von fermentierten Fleischprodukten zur Umrötung, charakteristischen Aromabildung sowie zur Gewähr¬leistung der Produktstabilität eingesetzt. Traditionell enthalten Starterkulturen KNS der Spezies S. carnosus und S. xylosus, aber auch andere KNS Spezies wie S. condimenti, S. piscifermentans, S. equorum und S. succinus haben ein Potential für den zukünftigen Einsatz in Starter¬kulturen. Die Sicherheit von fermentierten Lebensmitteln basiert zumeist auf Langzeiterfahrung infolge der sicheren Historie von traditionellen Methoden. Zuletzt genannte Spezies haben jedoch nur eine eingeschränkte Langzeiterfahrung hinsichtlich der gesundheit¬lichen Unbedenklichkeit. Zur Bestimmung sicherheitsrelevanter Eigenschaften von lebensmittelassoziierten KNS wur¬den im Kapitel III-V Stämme der Spezies S. carnosus, S. condimenti und S. piscifermentans (S. carnosus-Gruppe) sowie S. equorum, S. succinus und S. xylosus (S. xylosus-Gruppe) phäno¬typisch und teils genotypisch untersucht. Weiterführend wurde im Kapitel VI ein DNA-Chip zum schnellen und simultanen Nachweis sicherheitsrelevanter Eigenschaften in KNS mit zu¬künftigem Einsatz in der Lebensmittelherstellung entwickelt. Um das Anwendungspotential des DNA-Chips zu erhöhen wurden bei der Konzeption des Chips technologisch relevante Eigenschaften mitberücksichtigt. Anschließend wurden phänotypisch charakterisierte KNS mit dem entwickelten Chip genotypisch auf sicherheitsrelevante Eigenschaften untersucht. In Kapitel III wurden 330 KNS der S. carnosus- und S. xylosus-Gruppe isoliert aus Lebensmitteln und Starterkulturen phänotypisch hinsichtlich der Resistenzen gegenüber 21 Antibiotika charakterisiert sowie die Resistenzgene blaZ, lnuA und tetK in Stämmen mit phänotypischer ß-Lactam-, Lincomycin- und Tetracyclin-Resistenz bestimmt. Die Studie beschreibt Antibiotikaresistenzprofile von Stämmen der Spezies S. equorum, S. succinus und S. piscifermentans und gibt durch die hohe Anzahl an untersuchten Stämmen einen Einblick in das Vorkommen von Antibiotika¬resistenzen in lebensmittelassoziierten KNS. In Kapitel IV wird die Bildung von Toxinen in lebensmittelassoziierten KNS der S. carnosus- und S. xylosus-Gruppe untersucht. Die hämolytische Aktivität auf Human- und Schafblutagar wurde von 330 Stämmen aus Lebensmitteln, Starterkulturen und klinischen Isolaten bestimmt sowie die Bildung von Staphylokokken-Enterotoxinen, Toxischen Schocksyndrom Toxin 1 und Exfoliativen Toxin A von 35 Stämmen mittels Immunoblot-Verfahrens. Das Kapitel zeigt, dass KNS die vielfach in fermentierten Lebensmitteln vorkommen, nicht generell als sicher betrach¬tet werden können. Um negative Effekte auf die humane Gesundheit zu vermeiden sollte das toxigene Potential von in der Lebensmittelherstellung eingesetzten Stämmen bestimmt werden. Kapitel V befasst sich mit der Bildung von Bindeproteinen an Extrazelluläre Matrixproteine (EZM) und von biogenen Aminen (BA) in 32 KNS Stämmen der S. carnosus- und S. xylosus-Gruppe. Die Bindekapazitäten an die EZM Fibronektin und Fibrinogen wurden mittels Mikrotiterplatten-Assays durch Fluoreszenzdetektion markierter Bakterienzellen an mit EZM beschichtete Mikrotiterplatten bestimmt. Die Bildung sechs wichtiger BA wurde mit HPLC sowie wachsenden und ruhenden Zellen untersucht. Dieses Kapitel demonstriert, das lebens¬mittelassoziierte KNS in der Lage sind unerwünschte Eigenschaften wie Bindeproteine an EZM und BA zu bilden. Daher ist weiterer Forschungsbedarf bezüglich potentieller Risiken und der Bedeutung in der menschlichen Gesundheit erforderlich, wenn Stämme mit diesen Eigen¬schaften zur Herstellung fermentierter Lebensmittel eingesetzt werden. Kapitel VI beschreibt die Konzeption eines Polynukleotid-basierenden DNA-Chips als Hilfs¬mittel zum Screenen von Genen mit möglicher gesundheitlicher und technologischer Rele¬vanz in lebensmittelassoziierten KNS. Auf dem DNA-Chip sind 220 Gene für Antibiotika¬resistenzen, Hämolysine, Toxine, Aminosäuredecarboxylasen (BA Bildung), EZM Binde¬proteine, Lipasen, Proteasen, Nitratatmung, Salz- und oxidative Stresstoleranz abgelegt. Die Hybridisierungen wurden mit genomischer DNA von 32, in Kapitel III-V phänotypisch unter¬suchten KNS, durchgeführt und können z.B. die Antibiotikaresistenzgene blaZ, lnuA, und tetK nachweisen. Gene, die für Decarboxylasen sowie Fibronektin- und Fibrinogen-Bindeproteine kodieren zeigten selten Übereinstimmung mit dem Phänotyp. Toxingene wurden nicht nach¬gewiesen. Technologisch relevante Gene (Proteasen, Lipasen, Katalase, Superoxiddismutase und Gene der dissimilatorischen Nitratreduktion) resultierten in Hybridisierungssignalen. Die Ergebnisse tragen zum Wissen über sicherheitsrelevante Eigenschaften lebensmittel¬assoziierter KNS bei, welches für eine präzise Sicherheitsbewertung erforderlich ist. Ein Vergleich der Ergebnisse aus Kapitel III-V und Kapitel VI zeigt, dass in der S. xylosus-Gruppe Antibiotika¬resistenzen sowie die Bildung von Toxinen und Bindeproteinen an EZM häufiger vorkommen als in der S. carnosus-Gruppe. Bei der Sicherheitsbewertung lebensmittel¬assoziierter KNS kann der konzipierte DNA-Chip als Hilfsmittel für ein kombi¬niertes Screening sicherheits- und technologisch relevanter Eigenschaften (Nitratreduktion, Kontrolle oxidativer Abbau durch Katalase, Geschmack- und Aromaverbesserung durch Proteasen und Lipasen) herangezogen werden. Zusammenfassend trägt der DNA-Chip dazu bei die Auswahlkriterien von KNS, die als Starterorganismen verwendet werden, hinsichtlich der Lebensmittelsicherheit und technologisch relevanter Eigenschaften zu verbessern

Cuerpos de mujeres* en resistencia al extractivismo y a la destrucción medioambiental: perspectivas feministas ecocríticas sobre artistas* latinoamericanas

Mientras nuestro mundo se encamina hacia una terrible crisis climática que ya está afectando diariamente a innumerables animales, plantas y personas—especialmente mujeres*—la espiral destructiva de nuestro sistema económico global sigue girando, como demuestra una mirada al creciente número de proyectos extractivistas en América Latina. Al mismo tiempo, la resistencia a la expropiación de tierras, a las relaciones asimétricas de poder, a los feminicidios y a la contaminación medioambiental es omnipresente y también se tematiza, en particular, a través de intervenciones artísticas en el espacio público. Este artículo aborda tres de estas intervenciones artísticas analizando las obras de dos artistas* latinoamericanas y de un grupo de artistas* de Chile, Argentina y Uruguay. Se analiza en qué medida las distintas obras—instalaciones, performances, arte callejero—abordan temas como la corporalidad femenina*, la destrucción del medio ambiente y el extractivismo, así como una mirada ecocrítica-feminista sobre las obras y la imbricación de cuerpos y territorios.While our world is heading towards a terrible climate crisis that is already affecting countless animals, plants and people—especially women*2—on a daily basis, the destructive spiral of our global economic system persists. A case in this point is the increasing number of extractivist projects in Latin America. At the same time, resistance to land expropriation, asymmetrical power relations, femicides and environmental pollution is omnipresent and is also thematised in particular through artistic interventions in public spaces. This article takes up three such art interventions by analysing the artworks of two Latin Americanartists and a group of artists from Chile, Argentina and Uruguay. It analyses the extent to which the various artworks—installation art, performance art, street art—deal with themes such as female* corporeality, environmental destruction and extractivism, as well as taking an ecocritical-feminist look at the artworks and the interweaving of bodies and territories