XZ: Deriving redshifts from X-ray spectra of obscured AGN

Context: Redshifts are fundamental for our understanding of extragalactic X-ray sources. Ambiguous counterpart associations, expensive optical spectroscopy and/or multimission multiwavelength coverage to resolve degeneracies make estimation often difficult in practice. Aims: We attempt to constrain redshifts of obscured Active Galactic Nuclei (AGN) using only low-resolution X-ray spectra. Methods: Our XZ method fits AGN X-ray spectra with a moderately complex spectral model incorporating a corona, torus obscurer and warm mirror. Using the Bayesian X-ray Astronomy (BXA) package, we constrain redshift, column density, photon index and luminosity simultaneously. The redshift information primarily comes from absorption edges in Compton-thin AGN, and from the Fe K$\alpha$ fluorescent line in heavily obscured AGN. A new generic background fitting method allows us to extract more information from limited numbers of source counts. Results: We derive redshift constraints for 74/321 hard-band detected sources in the Chandra deep field South. Comparing with spectroscopic redshifts, we find an outlier fraction of 8%, indicating that our model assumptions are valid. For three Chandra deep fields, we release our XZ redshift estimates. Conclusions: The independent XZ estimate is easy to apply and effective for a large fraction of obscured AGN in todays deep surveys without the need for any additional data. Comparing to different redshift estimation methods, XZ can resolve degeneracies in photometric redshifts, help to detect potential association problems and confirm uncertain single-line spectroscopic redshifts. With high spectral resolution and large collecting area, this technique will be highly effective for Athena/WFI observations.Comment: 20 pages, 16 figures in paper, 14 in appendice

Physiological and genetic description of dissimilatory perchlorate reduction by the novel marine bacterium Arcobacter sp. strain CAB.

A novel dissimilatory perchlorate-reducing bacterium (DPRB), Arcobacter sp. strain CAB, was isolated from a marina in Berkeley, CA. Phylogenetically, this halophile was most closely related to Arcobacter defluvii strain SW30-2 and Arcobacter ellisii. With acetate as the electron donor, strain CAB completely reduced perchlorate (ClO4(-)) or chlorate (ClO3(-)) [collectively designated (per)chlorate] to innocuous chloride (Cl(-)), likely using the perchlorate reductase (Pcr) and chlorite dismutase (Cld) enzymes. When grown with perchlorate, optimum growth was observed at 25 to 30°C, pH 7, and 3% NaCl. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) preparations were dominated by free-swimming straight rods with 1 to 2 polar flagella per cell. Strain CAB utilized a variety of organic acids, fructose, and hydrogen as electron donors coupled to (per)chlorate reduction. Further, under anoxic growth conditions strain CAB utilized the biogenic oxygen produced as a result of chlorite dismutation to oxidize catechol via the meta-cleavage pathway of aerobic catechol degradation and the catechol 2,3-dioxygenase enzyme. In addition to (per)chlorate, oxygen and nitrate were alternatively used as electron acceptors. The 3.48-Mb draft genome encoded a distinct perchlorate reduction island (PRI) containing several transposases. The genome lacks the pcrC gene, which was previously thought to be essential for (per)chlorate reduction, and appears to use an unrelated Arcobacter c-type cytochrome to perform the same function. IMPORTANCE The study of dissimilatory perchlorate-reducing bacteria (DPRB) has largely focused on freshwater, mesophilic, neutral-pH environments. This study identifies a novel marine DPRB in the genus Arcobacter that represents the first description of a DPRB associated with the Campylobacteraceae. Strain CAB is currently the only epsilonproteobacterial DPRB in pure culture. The genome of strain CAB lacks the pcrC gene found in all other DPRB tested, demonstrating a new variation on the (per)chlorate reduction pathway. The ability of strain CAB to oxidize catechol via the oxygenase-dependent meta-cleavage pathway in the absence of external oxygen by using the biogenic oxygen produced from the dismutation of chlorite provides a valuable model for understanding the anaerobic degradation of a broad diversity of xenobiotics which are recalcitrant to anaerobic metabolism but labile to oxygenase-dependent mechanisms

Mit RFID zu besserem Service und neuen Strukturen – das Beispiel UB Leipzig

Am Beispiel der Universitätsbibliothek Leipzig werden die notwendigen organisatorischen Veränderungen beim RFID-Einsatz erläutert.Taking as example the Leipzig University Library, the necessary organisational changes for the use of RFID are explained

Addiction History Associates with the Propensity to Form Habits

Learned habitual responses to environmental stimuli allow efficient interaction with the environment, freeing cognitive resources for more demanding tasks. However, when the outcome of such actions is no longer a desired goal, established stimulus-response (S-R) associations, or habits, must be overcome. Among people with substance use disorders (SUDs), difficulty in overcoming habitual responses to stimuli associated with their addiction in favor of new, goal-directed behaviors, contributes to relapse. Animal models of habit learning demonstrate that chronic self-administration of drugs of abuse promotes habitual responding beyond the domain of compulsive drug seeking. However, whether a similar propensity toward domain-general habitual responding occurs in humans with SUDs has remained unclear. To address this question, we used a visuomotor S-R learning and re-learning task, the Hidden Association Between Images Task (HABIT), which employs abstract visual stimuli and manual responses. This task allows us to measure new S-R association learning, well-learned S-R association execution, and includes a response contingency change manipulation to quantify the degree to which responding is habit-based, rather than goal-directed. We find that people with SUDs learn new S-R associations as well as healthy control subjects do. Moreover, people with an SUD history slightly outperform controls in S-R execution. In contrast, people with SUDs are specifically impaired in overcoming well-learned S-R associations; those with SUDs make a significantly greater proportion of perseverative errors during well-learned S-R replacement, indicating the more habitual nature of their responses. Thus, with equivalent training and practice, people with SUDs appear to show enhanced domain-general habit formation

(Per)chlorate-reducing bacteria can utilize aerobic and anaerobic pathways of aromatic degradation with (per)chlorate as an electron acceptor.

UnlabelledThe pathways involved in aromatic compound oxidation under perchlorate and chlorate [collectively known as (per)chlorate]-reducing conditions are poorly understood. Previous studies suggest that these are oxygenase-dependent pathways involving O2 biogenically produced during (per)chlorate respiration. Recently, we described Sedimenticola selenatireducens CUZ and Dechloromarinus chlorophilus NSS, which oxidized phenylacetate and benzoate, two key intermediates in aromatic compound catabolism, coupled to the reduction of perchlorate or chlorate, respectively, and nitrate. While strain CUZ also oxidized benzoate and phenylacetate with oxygen as an electron acceptor, strain NSS oxidized only the latter, even at a very low oxygen concentration (1%, vol/vol). Strains CUZ and NSS contain similar genes for both the anaerobic and aerobic-hybrid pathways of benzoate and phenylacetate degradation; however, the key genes (paaABCD) encoding the epoxidase of the aerobic-hybrid phenylacetate pathway were not found in either genome. By using transcriptomics and proteomics, as well as by monitoring metabolic intermediates, we investigated the utilization of the anaerobic and aerobic-hybrid pathways on different electron acceptors. For strain CUZ, the results indicated utilization of the anaerobic pathways with perchlorate and nitrate as electron acceptors and of the aerobic-hybrid pathways in the presence of oxygen. In contrast, proteomic results suggest that strain NSS may use a combination of the anaerobic and aerobic-hybrid pathways when growing on phenylacetate with chlorate. Though microbial (per)chlorate reduction produces molecular oxygen through the dismutation of chlorite (ClO2(-)), this study demonstrates that anaerobic pathways for the degradation of aromatics can still be utilized by these novel organisms.ImportanceS. selenatireducens CUZ and D. chlorophilus NSS are (per)chlorate- and chlorate-reducing bacteria, respectively, whose genomes encode both anaerobic and aerobic-hybrid pathways for the degradation of phenylacetate and benzoate. Previous studies have shown that (per)chlorate-reducing bacteria and chlorate-reducing bacteria (CRB) can use aerobic pathways to oxidize aromatic compounds in otherwise anoxic environments by capturing the oxygen produced from chlorite dismutation. In contrast, we demonstrate that S. selenatireducens CUZ is the first perchlorate reducer known to utilize anaerobic aromatic degradation pathways with perchlorate as an electron acceptor and that it does so in preference over the aerobic-hybrid pathways, regardless of any oxygen produced from chlorite dismutation. D. chlorophilus NSS, on the other hand, may be carrying out anaerobic and aerobic-hybrid processes simultaneously. Concurrent use of anaerobic and aerobic pathways has not been previously reported for other CRB or any microorganisms that encode similar pathways of phenylacetate or benzoate degradation and may be advantageous in low-oxygen environments

Books around the clock. Sachsens erste 24-Stunden-Bibliothek

Unter diesem Motto wurde am 23. Oktober 2009 die Campus-Bibliothek der Universität Leipzig als 24-Stunden-Bibliothek am Augustusplatz feierlich eröffnet. Nach vierjähriger Bauzeit und noch längerer Planung hatte die Bibliothek am 28. September ihren Betrieb aufgenommen. Sie bietet auf 5.000 m2 Platz für 500.000 Bände, vorerst sind wir mit knapp 300.000 Bänden eingezogen. Die Campus-Bibliothek ist Teil des neu rekonstruierten Hörsaalgebäudes und bildet einen wichtigen Meilenstein bei der Errichtung des neuen Universitätscampus im Herzen von Leipzig

Gemeinsam und doch für sich

Die Qualität von Arbeitsergebnissen steht und fällt mit den Bedingungen am Arbeitsplatz. Das ist nicht nur im akademischen Bereich so. Um vor allem Promovierenden der geisteswissenschaftlichen Bereiche eine gute Basis zu bieten, hat die Universitätsbibliothek Leipzig eine besondere Art von Großraumbüro geschaffen

„Mehr“ Bibliothek durch weniger Handgriffe?: Von Selbstverbuchung und Serviceerweiterung

Längst wissen alle im Bibliotheksgeschäft Tätigen, dass Bibliotheken auch oder gerade in Zeiten von E-Books und Online-Journalen begehrte Arbeits- und Lernorte sind. Überfüllte Lesebereiche, Forderungen nach langen Öffnungszeiten und diversen Arbeitsplatzqualitäten sprechen eine deutliche Sprache. Diesen berechtigten Wünschen stehen jedoch meist knappe Mittel gegenüber und es stellt sich die Frage, wie wir zusätzlichen Service mit gleichbleibenden oder sinkenden Ressourcen leisten können. Was also liegt näher, als bestimmte Abläufe durch Automaten zu ersetzen? Damit könnten Kapazitäten frei werden, mit denen dieses besondere „Mehr“, das eine lebendige Bibliothek heute ausmacht, geboten werden kann

Mein Traum von Bibliothek

Unter dem Titel „Mein Traum von Bibliothek“ wird demnächst an der Universitätsbibliothek Leipzig eine Vortragsreihe für Bibliothekare starten. Thema ist der von uns allen erlebte rasante Wandel in der Mediennutzung durch digitale Technik. Die Aufgaben der Bibliothek ändern sich, die Tätigkeiten der Bibliothekare ändern sich, die Funktionen der Bibliotheksräume ändern sich. Das hat Konsequenzen für alle wissenschaftlichen Bibliotheken, ins besondere für ein komplexes System wie das der UB Leipzig mit derzeit noch 19 Zweigbibliotheken. Welche Räume hat eine Bibliothek, wenn sowohl die Informationen wie die Wege dahin digital formatiert sind? Welcher Service sollte geboten werden

Prüfungsevaluationen und damit verbundene Feedbackgespräche. Wie sie zur Hochschulentwicklung beitragen können

Die Autorinnen stellen auf der Grundlage zehnjähriger Erfahrung mit der Evaluation summativer Prüfungen dar, wie mit der Veränderung des Prüfungssystems eines Studiengangs auf die Verbesserung der Lehrqualität Einfluss genommen werden kann. Sie legen dar, wie nicht nur die Lehre, sondern auch die Prüfungen institutionell evaluiert werden und somit Prüfungen als Instrument zur Kompetenzentwicklung und Evaluationen als Innovationsförderung zu verstehen sind. (DIPF/Orig.