4,466 research outputs found
Emission within a Damped Lyman Alpha Absorption Trough: the Complex Sight Line Towards Q2059-360
We present new spectroscopic observations of the quasar Q2059-360, confirming
the existence of an emission feature within the Damped Lyman Alpha (DLA)
absorption trough. By observing also at slit positions offset from the quasar,
we show that the emission is spatially extended by at least a few arcseconds,
and hence confirm that the feature seen must be due to emission rather than
unusual absorption characteristics. We find that the DLA trough is very close
in redshift to the broad Lyman~ emission line of the QSO, with the
result that the DLA absorption removes much of the peak region of that line.
Despite the similarity of the redshifts of the DLA and the QSO, the lack of
high-ionization lines of the DLA system and the unresolved widths of the
corresponding metal lines indicate that the DLA cloud is not an associated
system. The emission feature has a large velocity offset of +490 km/s with
respect to the DLA system, and is resolved in velocity, comprising two
components with a separation of ~ 300 km/s. We consider three possibilities:
(1) Both emission and absorption occur within an object similar to the high
redshift Lyman-break galaxies; (2) The emission feature arises from an object
distinct from both the DLA absorber and the QSO, perhaps a young star-forming
galaxy or a proto-galactic clump. It could be associated with the DLA absorber
and perhaps the QSO in a compact group or cluster; (3) The redshifts are such
that the emission feature could be due to Narrow Line Region filaments of the
QSO, if the DLA absorption covers a sufficiently small angular size to allow
the filaments to be seen beyond the edge of the DLA cloud.Comment: 10 pages, 6 figures. Accepted for publication in MNRA
Oomycete Diseases in the North-Central Region: A Survey of Certified Crop Advisers
This report presents the results of a web-based survey of certified crop advisers conducted as part of the Integrated Management of Oomycete Diseases of Soybean and other Crop Plants Project funded by USDA-NIFA. The survey represents a first step in a project-long effort to engage members of the Certified Crop Adviser (CCA) program of the American Society of Agronomy in educational and extension activities focused on improving their ability to accurately diagnose and manage soybean seedling and root diseases, particularly those caused by oomycetes. The report consists of two sections. This first section describes the survey’s objectives and methods. The second section contains the tabulated data
Simulating a dual beam combiner at SUSI for narrow-angle astrometry
The Sydney University Stellar Interferometer (SUSI) has two beam combiners,
i.e. the Precision Astronomical Visible Observations (PAVO) and the
Microarcsecond University of Sydney Companion Astrometry (MUSCA). The primary
beam combiner, PAVO, can be operated independently and is typically used to
measure properties of binary stars of less than 50 milliarc- sec (mas)
separation and the angular diameters of single stars. On the other hand, MUSCA
was recently installed and must be used in tandem with the for- mer. It is
dedicated for microarcsecond precision narrow-angle astrometry of close binary
stars. The performance evaluation and development of the data reduction
pipeline for the new setup was assisted by an in-house computer simulation tool
developed for this and related purposes. This paper describes the framework of
the simulation tool, simulations carried out to evaluate the performance of
each beam combiner and the expected astrometric precision of the dual beam
combiner setup, both at SUSI and possible future sites.Comment: 28 pages, 23 figures, accepted for publication in Experimental
Astronomy. The final publication is available at http://link.springer.co
Assessment of Certified Crop Adviser Experience with and Knowledge of Early and Mid-season Soybean Diseases Caused by Oomycetes: 2015
This report presents the results of a web-based survey of certified crop advisers (CCAs) conducted as part of the Integrated Management of Oomycete Diseases of Soybean and other Crop Plants Project funded by USDA-NIFA. The survey is part of a project-long effort to engage members of the Certified Crop Adviser program of the American Society of Agronomy and other crop advisers in educational and extension activities to improve their ability to accurately diagnose and manage soybean seedling and root diseases, particularly those caused by oomycetes. The report consists of three sections. This first section describes the survey’s objectives and methods. The second section presents selected results. The third section presents the full results of the survey in tabulated form
Assessment of Certified Crop Adviser Experience with and Knowledge of Early and Mid-season Soybean Diseases Caused by Oomycetes
This report presents the results of a web-based survey of certified crop advisers (CCAs) conducted as part of the Integrated Management of Oomycete Diseases of Soybean and other Crop Plants Project funded by USDA-NIFA. The survey is part of a project-long effort to engage members of the Certified Crop Adviser program of the American Society of Agronomy and other crop advisers in educational and extension activities focused on improving their ability to accurately diagnose and manage soybean seedling and root diseases, particularly those caused by oomycetes. The report consists of three sections. This first section describes the survey’s objectives and methods. The second section presents selected results. The third section presents the full results of the survey in tabulated form
Compact high-resolution spectrographs for large and extremely large telescopes: using the diffraction limit
As telescopes get larger, the size of a seeing-limited spectrograph for a
given resolving power becomes larger also, and for ELTs the size will be so
great that high resolution instruments of simple design will be infeasible.
Solutions include adaptive optics (but not providing full correction for short
wavelengths) or image slicers (which give feasible but still large
instruments). Here we develop the solution proposed by Bland-Hawthorn and
Horton: the use of diffraction-limited spectrographs which are compact even for
high resolving power. Their use is made possible by the photonic lantern, which
splits a multi-mode optical fiber into a number of single-mode fibers. We
describe preliminary designs for such spectrographs, at a resolving power of R
~ 50,000. While they are small and use relatively simple optics, the challenges
are to accommodate the longest possible fiber slit (hence maximum number of
single-mode fibers in one spectrograph) and to accept the beam from each fiber
at a focal ratio considerably faster than for most spectrograph collimators,
while maintaining diffraction-limited imaging quality. It is possible to obtain
excellent performance despite these challenges. We also briefly consider the
number of such spectrographs required, which can be reduced by full or partial
adaptive optics correction, and/or moving towards longer wavelengths.Comment: 13 pages, 8 figures. To be published in Proceedings of the SPIE,
Volume 8446, paper 8446-7
A low cost scheme for high precision dual-wavelength laser metrology
A novel method capable of delivering relative optical path length metrology
with nanometer precision is demonstrated. Unlike conventional dual-wavelength
metrology which employs heterodyne detection, the method developed in this work
utilizes direct detection of interference fringes of two He-Ne lasers as well
as a less precise stepper motor open-loop position control system to perform
its measurement. Although the method may be applicable to a variety of
circumstances, the specific application where this metrology is essential is in
an astrometric optical long baseline stellar interferometer dedicated to
precise measurement of stellar positions. In our example application of this
metrology to a narrow-angle astrometric interferometer, measurement of
nanometer precision could be achieved without frequency-stabilized lasers
although the use of such lasers would extend the range of optical path length
the metrology can accurately measure. Implementation of the method requires
very little additional optics or electronics, thus minimizing cost and effort
of implementation. Furthermore, the optical path traversed by the metrology
lasers is identical with that of the starlight or science beams, even down to
using the same photodetectors, thereby minimizing the non-common-path between
metrology and science channels.Comment: 17 pages, 4 figures, accepted for publication in Applied Optic
The anti-adhesive effect of curcumin on Candida albicans biofilms on denture materials
The use of natural compounds as an alternative source of antimicrobials has become a necessity given the growing concern over global antimicrobial resistance. Polyphenols, found in various edible plants, offers one potential solution to this. We aimed to investigate the possibility of using curcumin within the context of oral health as a way of inhibiting and preventing the harmful development of Candida albicans biofilms. We undertook a series of adsorption experiments with varying concentrations of curcumin, showing that 50 ug/ml could prevent adhesion. This effect could be further synergised by the curcumin pretreatment of yeast cells to obtain significantly greater inhibition (>90, p<0.001). Investigation of the biological impact of curcumin showed that it preferentially affected immature morphological forms (yeast and germlings), and actively promoted aggregation of the cells. Transcriptional analyses showed that key adhesins were down-regulated (ALS1 and ALS3), whereas aggregation related genes (ALS5 and AAF1) were up-regulated. Collectively, these data demonstrated that curcumin elicits anti-adhesive effects and that induces transcription of genes integrally involved in the processes related to biofilm formation. Curcumin and associated polyphenols therefore have the capacity to be developed for use in oral healthcare to augment existing preventative strategies for candidal biofilms on the denture surface
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