11,351 research outputs found
Twisted split-ring-resonator photonic metamaterial with huge optical activity
Coupled split-ring-resonator metamaterials have previously been shown to
exhibit large coupling effects, which are a prerequisite for obtaining large
effective optical activity. By a suitable lateral arrangement of these building
blocks, we completely eliminate linear birefringence and obtain pure optical
activity and connected circular optical dichroism. Experiments at around
100-THz frequency and corresponding modeling are in good agreement. Rotation
angles of about 30 degrees for 205nm sample thickness are derived.Comment: 6 pages, 4 figure
Signal transducer and activator of transcription-1 localizes to the mitochondria and modulates mitophagy
The signal transducer and activator of transcription (STAT) proteins are latent transcription factors that have been shown to be involved in cell proliferation, development, apoptosis, and autophagy. STAT proteins undergo activation by phosphorylation at tyrosine 701 and serine 727 where they translocate to the nucleus to regulate gene expression. STAT1 has been shown to be involved in promoting apoptotic cell death in response to cardiac ischemia/reperfusion and has recently been shown by our laboratory to be involved in negatively regulating autophagy. These processes are thought to promote cell death and restrict cell survival leading to the generation of an infarct. Here we present data that shows STAT1 localizes to the mitochondria and co-immunoprecipitates with LC3. Furthermore, electron microscopy studies also reveal mitochondria from ex vivo I/R treated hearts of STAT1KO mice contained within a double membrane autophagosome indicating that STAT1 may be involved in negatively regulating mitophagy. This is the first description of STAT1 being localized to the mitochondria and also having a role in mitophagy
Molecular Gas during the Post-Starburst Phase: Low Gas Fractions in Green Valley Seyfert Post-Starburst Galaxies
Post-starbursts (PSBs) are candidate for rapidly transitioning from
star-bursting to quiescent galaxies. We study the molecular gas evolution of
PSBs at z ~ 0.03 - 0.2. We undertook new CO (2-1) observations of 22 Seyfert
PSBs candidates using the ARO Submillimeter Telescope. This sample complements
previous samples of PSBs by including green valley PSBs with Seyfert-like
emission, allowing us to analyze for the first time the molecular gas
properties of 116 PSBs with a variety of AGN properties. The distribution of
molecular gas to stellar mass fractions in PSBs is significantly different than
normal star-forming galaxies in the COLD GASS survey. The combined samples of
PSBs with Seyfert-like emission line ratios have a gas fraction distribution
which is even more significantly different and is broader (~ 0.03-0.3). Most of
them have lower gas fractions than normal star-forming galaxies. We find a
highly significant correlation between the WISE 12 micron to 4.6 micron flux
ratios and molecular gas fractions in both PSBs and normal galaxies. We detect
molecular gas in 27% of our Seyfert PSBs. Taking into account the upper limits,
the mean and the dispersion of the distribution of the gas fraction in our
Seyfert PSB sample are much smaller (mean = 0.025, std dev. = 0.018) than
previous samples of Seyfert PSBs or PSBs in general (mean ~ 0.1 - 0.2, std dev.
~ 0.1 - 0.2).Comment: 17 pages, 12 figures accepted in MNRA
Voyager 1 and 2 measurements of radial and latitudinal cosmic ray gradients during 1981 - 1984
The cosmic ray radial gradient was determined during 1981-84 using data from very similar detectors onboard spacecraft Voyagers 1 and 2 (radial separation approx. 6 AU, heliolatitude separation approx. 25 deg.) and from the Earth-orbiting satellite IMP 8. The principal result is that the radial gradient over this period decreased at the rate approx. 2.0%/AU between 1 and 16 AU and approx. 0.6%/AU between approx. 16 and 22 AU
Proof of Luck: an Efficient Blockchain Consensus Protocol
In the paper, we present designs for multiple blockchain consensus primitives
and a novel blockchain system, all based on the use of trusted execution
environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using
TEEs for existing proof of work schemes can make mining equitably distributed
by preventing the use of ASICs. Next, we extend the design with proof of time
and proof of ownership consensus primitives to make mining energy- and
time-efficient. Further improving on these designs, we present a blockchain
using a proof of luck consensus protocol. Our proof of luck blockchain uses a
TEE platform's random number generation to choose a consensus leader, which
offers low-latency transaction validation, deterministic confirmation time,
negligible energy consumption, and equitably distributed mining. Lastly, we
discuss a potential protection against up to a constant number of compromised
TEEs.Comment: SysTEX '16, December 12-16, 2016, Trento, Ital
Is the magnetic field in the heliosheath laminar or a turbulent bath of bubbles?
All the current global models of the heliosphere are based on the assumption
that the magnetic field in the heliosheath, in the region close to the
heliopause is laminar. We argue that in that region the heliospheric magnetic
field is not laminar but instead consists of magnetic bubbles. Recently, we
proposed that the annihilation of the "sectored" magnetic field within the
heliosheath as it is compressed on its approach to the heliopause produces the
anomalous cosmic rays and also energetic electrons. As a product of the
annihilation of the sectored magnetic field, densely-packed magnetic
islands/bubbles are produced. These magnetic islands/bubbles will be convected
with the ambient flows as the sector region is carried to higher latitudes
filling the heliosheath. We further argue that the magnetic islands/bubbles
will develop upstream within the heliosheath. As a result, the magnetic field
in the heliosheath sector region will be disordered well upstream of the
heliopause. We present a 3D MHD simulation with very high numerical resolution
that captures the north-south boundaries of the sector region. We show that due
to the high pressure of the interstellar magnetic field a north-south asymmetry
develops such that the disordered sectored region fills a large portion of the
northern part of the heliosphere with a smaller extension in the southern
hemisphere. We suggest that this scenario is supported by the following changes
that occur around 2008 and from 2009.16 onward: a) the sudden decrease in the
intensity of low energy electrons detected by Voyager 2; b) a sharp reduction
in the intensity of fluctuations of the radial flow; and c) the dramatic
differences in intensity trends between GCRs at V1 and 2. We argue that these
observations are a consequence of V2 leaving the sector region of disordered
field during these periods and crossing into a region of unipolar laminar
field.Comment: 36 pages, 15 figures, submitted to Ap
The Impact of Free Radical Stabilization Techniques on In Vivo Property Changes in Highly Cross-Linked Polyethylene Acetabular Liners
Highly cross-linked polyethylene (HXLPE) was introduced into total hip arthroplasty (THA) to reduce long-term wear-related complications. However, HXLPE production and in vivo oxidation can alter mechanical behavior. Mechanical failure of HXLPE liners at the implant rim have been reported. The purpose of this thesis is to determine if thermal free radical stabilization techniques used in HXLPE production alter the mechanical properties, physical properties and oxidative stability of liner rims after extended in vivo time.
Retrieved remelted, single annealed and sequentially annealed HXLPE liner rims were mechanically tested using a validated microindentation technique. Oxidation and crystalline phase composition were measured. Results demonstrated remelted liner rims had a decrease in mechanical properties but were oxidatively stable, whereas single and sequentially annealed liners demonstrated oxidation and increased crystallinity despite stable mechanical properties. This suggests mechanical properties change in vivo for certain implants, but this is not due to in vivo oxidation or altered crystallinity
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