1,463 research outputs found
Single or Double Degenerate Progenitors? Searching for Shock Emission in the SDSS-II Type Ia Supernovae
From the set of nearly 500 spectroscopically confirmed type~Ia supernovae and
around 10,000 unconfirmed candidates from SDSS-II, we select a subset of 108
confirmed SNe Ia with well-observed early-time light curves to search for
signatures from shock interaction of the supernova with a companion star. No
evidence for shock emission is seen; however, the cadence and photometric noise
could hide a weak shock signal. We simulate shocked light curves using SN Ia
templates and a simple, Gaussian shock model to emulate the noise properties of
the SDSS-II sample and estimate the detectability of the shock interaction
signal as a function of shock amplitude, shock width, and shock fraction. We
find no direct evidence for shock interaction in the rest-frame -band, but
place an upper limit on the shock amplitude at 9% of supernova peak flux ( mag). If the single degenerate channel dominates type~Ia progenitors,
this result constrains the companion stars to be less than about 6
on the main sequence, and strongly disfavors red giant companions.Comment: 28 pages, 3 figure
An Agenda for Increasing Grant Funding of Emergency Medicine Education Research
Funding is a perennial challenge for medical education researchers. Through a consensus process, the authors developed a multifaceted agenda for increasing funding of education research in emergency medicine ( EM ). Priority agenda items include developing resources to increase the competitiveness of medical education research faculty in grant applications, identifying means by which departments may bolster their faculty's grant writing success, taking longâterm steps to increase the number of grants available to education researchers in the field, and encouraging a shift in cultural attitudes toward education research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95395/1/acem12041.pd
Can Antiviral Drugs Contain Pandemic Influenza Transmission?
Antiviral drugs dispensed during the 2009 influenza pandemic generally failed to
contain transmission. This poses the question of whether preparedness for a
future pandemic should include plans to use antiviral drugs to mitigate
transmission
Rest and treatment/rehabilitation following sport-related concussion: a systematic review
AIM OR OBJECTIVE: The objective of this systematic review was to evaluate the evidence regarding rest and active treatment/rehabilitation following sport-related concussion (SRC).
DESIGN: Systematic review.
DATA SOURCES: MEDLINE (OVID), CINAHL (EbscoHost), PsycInfo (OVID), Cochrane Central Register of Controlled Trials (OVID), SPORTDiscus (EbscoHost), EMBASE (OVID) and Proquest DissertationsandTheses Global (Proquest) were searched systematically.
ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies were included if they met the following criteria: (1) original research; (2) reported SRC as the diagnosis; and (3) evaluated the effect of rest or active treatment/rehabilitation. Review articles were excluded.
RESULTS: Twenty-eight studies met the inclusion criteria (9 regarding the effects of rest and 19 evaluating active treatment). The methodological quality of the literature was limited; only five randomised controlled trials (RCTs) met the eligibility criteria. Those RCTs included rest, cervical and vestibular rehabilitation, subsymptom threshold aerobic exercise and multifaceted collaborative care.
SUMMARY/CONCLUSIONS: A brief period (24-48âhours) of cognitive and physical rest is appropriate for most patients. Following this, patients should be encouraged to gradually increase activity. The exact amount and duration of rest are not yet well defined and require further investigation. The data support interventions including cervical and vestibular rehabilitation and multifaceted collaborative care. Closely monitored subsymptom threshold, submaximal exercise may be of benefit.
SYSTEMATIC REVIEW REGISTRATION: PROSPERO 2016:CRD42016039570
Chemical Cartography with APOGEE: Large-scale Mean Metallicity Maps of the Milky Way
We present Galactic mean metallicity maps derived from the first year of the
SDSS-III APOGEE experiment. Mean abundances in different zones of
Galactocentric radius (0 < R < 15 kpc) at a range of heights above the plane (0
< |z| < 3 kpc), are derived from a sample of nearly 20,000 stars with
unprecedented coverage, including stars in the Galactic mid-plane at large
distances. We also split the sample into subsamples of stars with low and
high-[{\alpha}/M] abundance ratios. We assess possible biases in deriving the
mean abundances, and find they are likely to be small except in the inner
regions of the Galaxy. A negative radial gradient exists over much of the
Galaxy; however, the gradient appears to flatten for R < 6 kpc, in particular
near the Galactic mid-plane and for low-[{\alpha}/M] stars. At R > 6 kpc, the
gradient flattens as one moves off of the plane, and is flatter at all heights
for high-[{\alpha}/M] stars than for low-[{\alpha}/M] stars. Alternatively,
these gradients can be described as vertical gradients that flatten at larger
Galactocentric radius; these vertical gradients are similar for both low and
high-[{\alpha}/M] populations. Stars with higher [{\alpha}/M] appear to have a
flatter radial gradient than stars with lower [{\alpha}/M]. This could suggest
that the metallicity gradient has grown steeper with time or, alternatively,
that gradients are washed out over time by migration of stars.Comment: 16 pages, 12 figures, submitted to A
The Subluminous Supernova 2007qd: A Missing Link in a Family of Low-Luminosity Type Ia Supernovae
We present multi-band photometry and multi-epoch spectroscopy of the peculiar
Type Ia supernova (SN Ia) 2007qd, discovered by the SDSS-II Supernova Survey.
It possesses physical properties intermediate to those of the peculiar SN
2002cx and the extremely low-luminosity SN 2008ha. Optical photometry indicates
that it had an extraordinarily fast rise time of <= 10 days and a peak absolute
B magnitude of -15.4 +/- 0.2 at most, making it one of the most subluminous SN
Ia ever observed. Follow-up spectroscopy of SN 2007qd near maximum brightness
unambiguously shows the presence of intermediate-mass elements which are likely
caused by carbon/oxygen nuclear burning. Near maximum brightness, SN 2007qd had
a photospheric velocity of only 2800 km/s, similar to that of SN 2008ha but
about 4000 and 7000 km/s less than that of SN 2002cx and normal SN Ia,
respectively. We show that the peak luminosities of SN 2002cx-like objects are
highly correlated with both their light-curve stretch and photospheric
velocities. Its strong apparent connection to other SN 2002cx-like events
suggests that SN 2007qd is also a pure deflagration of a white dwarf, although
other mechanisms cannot be ruled out. It may be a critical link between SN
2008ha and the other members of the SN 2002cx-like class of objects.Comment: To be published in the Astrophysical Journal; 37 pages, 13 figures, 4
table
Synthesis, Biological Evaluation and Docking Studies of Ring-Opened Analogues of Ipomoeassin F
The plant-derived macrocyclic resin glycoside ipomoeassin F (Ipom-F) binds to Sec61α and significantly disrupts multiple aspects of Sec61-mediated protein biogenesis at the endoplasmic reticulum, ultimately leading to cell death. However, extensive assessment of Ipom-F as a molecular tool and a therapeutic lead is hampered by its limited production scale, largely caused by intramolecular assembly of the macrocyclic ring. Here, using in vitro and/or in cellula biological assays to explore the first series of ring-opened analogues for the ipomoeassins, and indeed all resin glycosides, we provide clear evidence that macrocyclic integrity is not required for the cytotoxic inhibition of Sec61-dependent protein translocation by Ipom-F. Furthermore, our modeling suggests that open-chain analogues of Ipom-F can interact with multiple sites on the Sec61α subunit, most likely located at a previously identified binding site for mycolactone and/or the so-called lateral gate. Subsequent in silico-aided design led to the discovery of the stereochemically simplified analogue 3 as a potent, alternative lead compound that could be synthesized much more efficiently than Ipom-F and will accelerate future ipomoeassin research in chemical biology and drug discovery. Our work may also inspire further exploration of ring-opened analogues of other resin glycosides
Synthesis, Biological Evaluation and Docking Studies of Ring-Opened Analogues of Ipomoeassin F
The plant-derived macrocyclic resin glycoside ipomoeassin F (Ipom-F) binds to Sec61α
and significantly disrupts multiple aspects of Sec61-mediated protein biogenesis at the endoplas mic reticulum, ultimately leading to cell death. However, extensive assessment of Ipom-F as a
molecular tool and a therapeutic lead is hampered by its limited production scale, largely caused
by intramolecular assembly of the macrocyclic ring. Here, using in vitro and/or in cellula biological
assays to explore the first series of ring-opened analogues for the ipomoeassins, and indeed all resin
glycosides, we provide clear evidence that macrocyclic integrity is not required for the cytotoxic
inhibition of Sec61-dependent protein translocation by Ipom-F. Furthermore, our modeling suggests
that open-chain analogues of Ipom-F can interact with multiple sites on the Sec61α subunit, most
likely located at a previously identified binding site for mycolactone and/or the so-called lateral gate.
Subsequent in silico-aided design led to the discovery of the stereochemically simplified analogue 3
as a potent, alternative lead compound that could be synthesized much more efficiently than Ipom-F
and will accelerate future ipomoeassin research in chemical biology and drug discovery. Our work
may also inspire further exploration of ring-opened analogues of other resin glycosides
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