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

Development of Novel Radiotherapy Treatment Monitoring and Quantitative Cherenkov Surface Dosimetry for Diverse Populations

In the U.S. alone, nearly 2 million people will be diagnosed with cancer annually, and over half of them will receive radiation therapy throughout the course of their care. While widely regarded as safe, radiation therapy presents unique challenges that other procedures, such as surgery, lack. Namely, the invisible nature of the radiation itself makes it impossible to directly visualize treatment. Many immobilization and localization techniques exist to minimize the chance of incorrect radiation dose delivery, yet incidents still occur. Within the last decade, Cherenkov imaging has emerged as a new radiation therapy delivery verification technique. Cherenkov imaging is unique to other modalities because it allows for real-time visualization of beam delivery on the entire surface of the patient, showing light wherever dose is delivered. Beyond the ability to verify the extent of the treatment field, it has the potential to provide a 2D surrogate surface dose map. In this work, we exploit the unique nature of Cherenkov imaging for treatment delivery verification and incident detection in the radiation therapy clinic. This thesis focuses on several uses of Cherenkov imaging in the clinic, spanning from radiotherapy incident detection to quantitative in vivo dosimetry for diverse patient populations, independent of skin pigmentation. Cherenkov imaging is first explored as a tool for automatic incident detection during treatment, leveraging unique biological fiducials that are inherent to patient images. Expanding to quantitative in vivo dosimetry, the synergistic combination of Cherenkov imaging and scintillation dosimetry is presented as promising alternative to conventional dosimeters, with the unique ability to directly visualize measurement locations relative to the treatment field on the surface of the patient. Lastly, the longstanding concern regarding Cherenkov imaging for dark skin patients is addressed in a multi-institutional collaboration between Dartmouth Hitchcock Health and Moffitt Cancer Center, dedicated to imaging a diverse population, with the successful development of a patient-specific skin pigmentation calibration, a noteworthy advancement towards the realization of quantitative Cherenkov dosimetry