149 research outputs found
Intensity Variations of H Alpha and N II 6 583 A Lines in the Night Sky Spectrum
Intensity variations of H alpha and N II 6 583 A lines in night sky spectru
Glycine and Folate Ameliorate Models of Congenital Sideroblastic Anemia
Sideroblastic anemias are acquired or inherited anemias that result in a decreased ability to
synthesize hemoglobin in red blood cells and result in the presence of iron deposits in the
mitochondria of red blood cell precursors. A common subtype of congenital sideroblastic
anemia is due to autosomal recessive mutations in the SLC25A38 gene. The current treatment
for SLC25A38 congenital sideroblastic anemia is chronic blood transfusion coupled
with iron chelation. The function of SLC25A38 is not known. Here we report that the
SLC25A38 protein, and its yeast homolog Hem25, are mitochondrial glycine transporters
required for the initiation of heme synthesis. To do so, we took advantage of the fact that
mitochondrial glycine has several roles beyond the synthesis of heme, including the synthesis
of folate derivatives through the glycine cleavage system. The data were consistent with
Hem25 not being the sole mitochondrial glycine importer, and we identify a second SLC25
family member Ymc1, as a potential secondary mitochondrial glycine importer. Based on
these findings, we observed that high levels of exogenous glycine, or 5-aminolevulinic acid
(5-Ala) a metabolite downstream of Hem25 in heme biosynthetic pathway, were able to
restore heme levels to normal in yeast cells lacking Hem25 function. While neither glycine
nor 5-Ala could ameliorate SLC25A38 congenital sideroblastic anemia in a zebrafish
model, we determined that the addition of folate with glycine was able to restore hemoglobin
levels. This difference is likely due to the fact that yeast can synthesize folate, whereas in
zebrafish folate is an essential vitamin that must be obtained exogenously. Given the tolerability
of glycine and folate in humans, this study points to a potential novel treatment for
SLC25A38 congenital sideroblastic anemia.Genome Canada as large-scale applied research project with funding contributions from the Dalhousie Medical Research Foundation, the Nova Scotia Research Innovation Trust, and the Nova Scotia Department of Health and Wellnes
Atomic step motion during the dewetting of ultra-thin films
We report on three key processes involving atomic step motion during the
dewetting of thin solid films: (i) the growth of an isolated island nucleated
far from a hole, (ii) the spreading of a monolayer rim, and (iii) the zipping
of a monolayer island along a straight dewetting front. Kinetic Monte Carlo
results are in good agreement with simple analytical models assuming
diffusion-limited dynamics.Comment: 7 pages, 5 figure
Suppression of the near-infrared OH night sky lines with fibre Bragg gratings - first results
The background noise between 1 and 1.8 microns in ground-based instruments is
dominated by atmospheric emission from hydroxyl molecules. We have built and
commissioned a new instrument, GNOSIS, which suppresses 103 OH doublets between
1.47 - 1.7 microns by a factor of ~1000 with a resolving power of ~10,000. We
present the first results from the commissioning of GNOSIS using the IRIS2
spectrograph at the AAT. The combined throughput of the GNOSIS fore-optics,
grating unit and relay optics is ~36 per cent, but this could be improved to
~46 per cent with a more optimal design. We measure strong suppression of the
OH lines, confirming that OH suppression with fibre Bragg gratings will be a
powerful technology for low resolution spectroscopy. The integrated OH
suppressed background between 1.5 and 1.7 microns is reduced by a factor of 9
compared to a control spectrum using the same system without suppression. The
potential of low resolution OH suppressed spectroscopy is illustrated with
example observations.
The GNOSIS background is dominated by detector dark current below 1.67
microns and by thermal emission above 1.67 microns. After subtracting these we
detect an unidentified residual interline component of ~ 860 +/ 210
ph/s/m^2/micron/arcsec^2. This component is equally bright in the suppressed
and control spectra. We have investigated the possible source of the interline
component, but were unable to discriminate between a possible instrumental
artifact and intrinsic atmospheric emission. Resolving the source of this
emission is crucial for the design of fully optimised OH suppression
spectrographs. The next generation OH suppression spectrograph will be focussed
on resolving the source of the interline component, taking advantage of better
optimisation for a FBG feed. We quantify the necessary improvements for an
optimal OH suppressing fibre spectrograph design.Comment: Accepted for publication in MNRAS. 15 pages, 18 figure
Formal verification of side-channel countermeasures using self-composition
Formal verification of cryptographic software implementations poses significant challenges for off-the-shelf tools. This is due to the domain-specific characteristics of the code, involving aggressive optimizations and non-functional security requirements, namely the critical aspect of countermeasures against side-channel attacks. In this paper, we extend previous results supporting the practicality of self-composition proofs of non-interference and generalizations thereof. We tackle the formal verification of high-level security policies adopted in the implementation of the recently proposed NaCl cryptographic library. We formalize these policies and propose a formal verification approach based on self-composition, extending the range of security policies that could previously be handled using this technique. We demonstrate our results by addressing compliance with the NaCl security policies in real-world cryptographic code, highlighting the potential for automation of our techniques.This work was partially supported by project SMART, funded by ENIAC joint Undertaking (GA 120224)
Cooking fish and drinking milk? Patterns in pottery use in the southeastern Baltic, 3300–2400 cal BC
yesA study of pottery vessel contents and use was undertaken in order to obtain information on food processed in Subneolithic and Neolithic vessels from Nida and Šventoji (3300–2400 cal BC). The aim is to assess pottery use during major changes in the coastal environment and in material culture. Bulk carbon and nitrogen isotope, lipid biomarker and compound specific carbon isotope analysis was undertaken on ‘foodcrusts’, charred deposits adhering to vessel surfaces, and absorbed residues from different vessel types. In addition, three archaeological seal bones were analysed for bulk collagen and compound specific carbon isotope analysis to establish collagen-lipid offsets to inform interpretation of the data. The results show that the majority of the vessels were used for processing aquatic products. At Nida the data suggest exploitation of freshwater resources and, in the later stages of occupation, dairying. Analysis of a small number of Subneolithic vessels from Šventoji produced results that are also consistent with processing of aquatic products. Other substances identified include Pinaceae sp. resin or tar and beeswax. These data demonstrate that identifying patterns in pottery use contributes to understanding Neolithisation processes
The case for OH suppression at near-infrared wavelengths
We calculate the advances in near-infrared astronomy made possible through
the use of fibre Bragg gratings to selectively remove hydroxyl emission lines
from the night sky spectrum. Fibre Bragg gratings should remove OH lines at
high resolution (R=10,000), with high suppression (30dB) whilst maintaining
high throughput (~90 per cent) between the lines. Devices currently under
construction should remove 150 lines in each of the J and H bands, effectively
making the night sky surface brightness ~4 magnitudes fainter. This background
reduction is greater than the improvement adapative optics makes over natural
seeing; photonic OH suppression is at least as important as adaptive optics for
the future of cosmology.
We present a model of the NIR sky spectrum, and show that the interline
continuum is very faint (~80 ph/s/m^s/arcsec/micron on the ecliptic plane). We
show that OH suppression by high dispersion, i.e. `resolving out' the skylines,
cannot obtain the required level of sensitivity to reach the interline
continuum due to scattering of light. The OH lines must be suppressed prior to
dispersion.
We have simulated observations employing fibre Bragg gratings of first light
objects, high redshift galaxies and cool, low-mass stars. The simulations are
of complete end-to-end systems from object to detector. The results demonstrate
that fibre Bragg grating OH suppression will significantly advance our
knowledge in many areas of astrophysics, and in particular will enable
rest-frame ultra-violet observations of the Universe at the time of first light
and reionisation.Comment: Accepted for publication in MNRA
M31N 2008-12a - the remarkable recurrent nova in M31: Pan-chromatic observations of the 2015 eruption
The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption ten times, including yearly eruptions from 2008-2014. With a measured recurrence period of days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground and space-based follow-up programs. In this paper we present the 2015 detection; visible to near-infrared photometry and visible spectroscopy; and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at Aug. UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities km s, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early super-soft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is d, and we expect the next eruption of M31N 2008-12a to occur around mid-Sep. 2016
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