139 research outputs found
A single Streptomyces symbiont makes multiple antifungals to support the fungus farming ant Acromyrmex octospinosus
Attine ants are dependent on a cultivated fungus for food and use antibiotics produced by symbiotic Actinobacteria as weedkillers in their fungus gardens. Actinobacterial species belonging to the genera Pseudonocardia, Streptomyces and Amycolatopsis have been isolated from attine ant nests and shown to confer protection against a range of microfungal weeds. In previous work on the higher attine Acromyrmex octospinosus we isolated a Streptomyces strain that produces candicidin, consistent with another report that attine ants use Streptomyces-produced candicidin in their fungiculture. Here we report the genome analysis of this Streptomyces strain and identify multiple antibiotic biosynthetic pathways. We demonstrate, using gene disruptions and mass spectrometry, that this single strain has the capacity to make candicidin and multiple antimycin compounds. Although antimycins have been known for > 60 years we report the sequence of the biosynthetic gene cluster for the first time. Crucially, disrupting the candicidin and antimycin gene clusters in the same strain had no effect on bioactivity against a co-evolved nest pathogen called Escovopsis that has been identified in similar to 30% of attine ant nests. Since the Streptomyces strain has strong bioactivity against Escovopsis we conclude that it must make additional antifungal(s) to inhibit Escovopsis. However, candicidin and antimycins likely offer protection against other microfungal weeds that infect the attine fungal gardens. Thus, we propose that the selection of this biosynthetically prolific strain from the natural environment provides A. octospinosus with broad spectrum activity against Escovopsis and other microfungal weeds.Publisher PDFPeer reviewe
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Retrieval cues fail to influence contextualized evaluations.
Initial evaluations generalise to new contexts, whereas counter-attitudinal evaluations are context-specific. Counter-attitudinal information may not change evaluations in new contexts because perceivers fail to retrieve counter-attitudinal cue-evaluation associations from memory outside the counter-attitudinal learning context. The current work examines whether an additional, counter-attitudinal retrieval cue can enhance the generalizability of counter-attitudinal evaluations. In four experiments, participants learned positive information about a target person, Bob, in one context, and then learned negative information about Bob in a different context. While learning the negative information, participants wore a wristband as a retrieval cue for counter-attitudinal Bob-negative associations. Participants then made speeded as well as deliberate evaluations of Bob while wearing or not wearing the wristband. Internal meta-analysis failed to find a reliable effect of the counter-attitudinal retrieval cue on speeded or deliberate evaluations, whereas the context cues influenced speeded and deliberate evaluations. Counter to predictions, counter-attitudinal retrieval cues did not disrupt the generalisation of first-learned evaluations or the context-specificity of second-learned evaluations (Experiments 2-4), but the counter-attitudinal retrieval cue did influence evaluations in the absence of context cues (Experiment 1). The current work provides initial evidence that additional counter-attitudinal retrieval cues fail to disrupt the renewal and generalizability of first-learned evaluations
The Direct Synthesis of H <sub>2</sub> O <sub>2</sub> Using TS-1 Supported Catalysts
In this study we show that using gold palladium nanoparticles supported on a commercial titanium silicate (TSâ1) prepared using a wet coâimpregnation method it is possible to produce hydrogen peroxide from molecular H2 and O2 via the direct synthesis reaction. The effect of Au: Pd ratio and calcination temperature is evaluated as well as the role of platinum addition to the AuPd supported catalysts. The effect of platinum addition to goldâpalladium nanoparticles is observed to result in a significant improvement in catalytic activity and selectivity to hydrogen peroxide with detailed characterisation indicating this is a result of selectively tuning the ratio of palladium oxidation states
Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey
The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed
to locate quasars during the epoch of reionization. In this paper we present
the discovery of the first four CFHQS quasars at redshift greater than 6,
including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We
describe the observational method used to identify the quasars and present
optical, infrared, and millimeter photometry and optical and near-infrared
spectroscopy. We investigate the dust properties of these quasars finding an
unusual dust extinction curve for one quasar and a high far-infrared luminosity
due to dust emission for another. The mean millimeter continuum flux for CFHQS
quasars is substantially lower than that for SDSS quasars at the same redshift,
likely due to a correlation with quasar UV luminosity. For two quasars with
sufficiently high signal-to-noise optical spectra, we use the spectra to
investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at
z=6.12, we find significant evolution (beyond a simple extrapolation of lower
redshift data) in the Gunn-Peterson optical depth at z>5.4. The line-of-sight
to this quasar has one of the highest known optical depths at z~5.8. An
analysis of the sizes of the highly-ionized near-zones in the spectra of two
quasars at z=6.12 and z=6.43 suggest the IGM surrounding these quasars was
substantially ionized before these quasars turned on. Together, these
observations point towards an extended reionization process, but we caution
that cosmic variance is still a major limitation in z>6 quasar observations.Comment: 15 pages, 9 figures, AJ, in press, minor changes to previous versio
Control-Value Appraisals, Enjoyment, and Boredom in Mathematics:A Longitudinal Latent Interaction Analysis
Based on the control-value theory of achievement emotions, this longitudinal study examined students' control-value appraisals as antecedents of their enjoyment and boredom in mathematics. Self-report data for appraisals and emotions were collected from 579 students in their final year of primary schooling over three waves. Data were analyzed using latent interaction structural equation modeling. Control-value appraisals predicted emotions interactively depending on which specific subjective value was paired with perceived control. Achievement value amplified the positive relation between perceived control and enjoyment, and intrinsic value reduced the negative relation between perceived control and boredom. These longitudinal findings demonstrate that control and value appraisals, and their interaction, are critically important for the development of students' enjoyment and boredom over time
Modern optical astronomy: technology and impact of interferometry
The present `state of the art' and the path to future progress in high
spatial resolution imaging interferometry is reviewed. The review begins with a
treatment of the fundamentals of stellar optical interferometry, the origin,
properties, optical effects of turbulence in the Earth's atmosphere, the
passive methods that are applied on a single telescope to overcome atmospheric
image degradation such as speckle interferometry, and various other techniques.
These topics include differential speckle interferometry, speckle spectroscopy
and polarimetry, phase diversity, wavefront shearing interferometry,
phase-closure methods, dark speckle imaging, as well as the limitations imposed
by the detectors on the performance of speckle imaging. A brief account is
given of the technological innovation of adaptive-optics (AO) to compensate
such atmospheric effects on the image in real time. A major advancement
involves the transition from single-aperture to the dilute-aperture
interferometry using multiple telescopes. Therefore, the review deals with
recent developments involving ground-based, and space-based optical arrays.
Emphasis is placed on the problems specific to delay-lines, beam recombination,
polarization, dispersion, fringe-tracking, bootstrapping, coherencing and
cophasing, and recovery of the visibility functions. The role of AO in
enhancing visibilities is also discussed. The applications of interferometry,
such as imaging, astrometry, and nulling are described. The mathematical
intricacies of the various `post-detection' image-processing techniques are
examined critically. The review concludes with a discussion of the
astrophysical importance and the perspectives of interferometry.Comment: 65 pages LaTeX file including 23 figures. Reviews of Modern Physics,
2002, to appear in April issu
Reviewing evidence of marine ecosystem change off South Africa
Recent changes have been observed in South African marine ecosystems. The main pressures on these
ecosystems are fishing, climate change, pollution, ocean acidification and mining. The best long-term datasets are
for trends in fishing pressures but there are many gaps, especially for non-commercial species. Fishing pressures
have varied over time, depending on the species being caught. Little information exists for trends in other
anthropogenic pressures. Field observations of environmental variables are limited in time and space. Remotely
sensed satellite data have improved spatial and temporal coverage but the time-series are still too short to
distinguish long-term trends from interannual and decadal variability. There are indications of recent cooling on the
West and South coasts and warming on the East Coast over a period of 20 - 30 years. Oxygen concentrations on the
West Coast have decreased over this period. Observed changes in offshore marine communities include southward
and eastward changes in species distributions, changes in abundance of species, and probable alterations in
foodweb dynamics. Causes of observed changes are difficult to attribute. Full understanding of marine ecosystem
change requires ongoing and effective data collection, management and archiving, and coordination in carrying out
ecosystem research.DHE
MFA10 (MFA 2010)
Catalogue of a culminating student exhibition held at the Mildred Lane Kemper Art Museum in 2010. Content includes Foreword / Buzz Spector -- Thinking as making / Robert Gero -- A new set of conversations / Patricia Olynyk -- MFA 2010 graduates. Clyde Ashby / Aaron Bos-Wahl / Andrew Cozzens / John Early / Ryan James Fabel / Joel Fullerton / Mary Beth Hassan / Wenting Hsu / John Nicholas Hutchings/ Dani Kantrowitz / Larry Keaty / Mamie Korpela / Paola Laterza / Mad Mohre / Emily Moorhead / Jonathan Muehlke / Jessa Richardson / Nicolette Ross / Carlie Trosclair / About the Sam Fox School.https://openscholarship.wustl.edu/books/1007/thumbnail.jp
Liquid â liquid phase separation morphologies in ultra-white beetle scales and a synthetic equivalent
Cyphochilus beetle scales are amongst the brightest structural whites in nature, being highly opacifying whilst extremely thin. However, the formation mechanism for the voided intra- scale structure is unknown. Here we report 3D x-ray nanotomography data for the voided chitin networks of intact white scales of Cyphochilus and Lepidiota stigma. Chitin-filling frac- tions are found to be 31 ± 2% for Cyphochilus and 34 ± 1% for Lepidiota stigma, indicating previous measurements overestimated their density. Optical simulations using finite- difference time domain for the chitin morphologies and simulated Cahn-Hilliard spinodal structures show excellent agreement. Reflectance curves spanning filling fraction of 5-95% for simulated spinodal structures, pinpoint optimal whiteness for 25% chitin filling. We make a simulacrum from a polymer undergoing a strong solvent quench, resulting in highly reflective ( 94%) white films. In-situ X-ray scattering confirms the nanostructure is formed through spinodal decomposition phase separation. We conclude that the ultra-white beetle scale nanostructure is made via liquidâliquid phase separation
368 CFHealthHub: development and evaluation of videos incorporating peer description of successful self-management with inhaled therapies in adults with CF used to build self-efficacy to support self-care within the CFHealthHub complex intervention
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