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

Density matrix renormalization group study of the interacting Kitaev chain with quasi-periodic disorder

We document the ground state phase diagram of the one-dimensional Kitaev chain with quasi-periodic disorder in the presence of two-body interactions. Our data was obtained for systems of $L=1000$ sites using large-scale density matrix renormalization group numerics and is benchmarked against known results for the clean system. We demonstrate that moderate quasi-periodic disorder stabilizes the topological phase both for repulsive and attractive interactions. For larger disorder strengths, the system features re-entrance behavior and multiple phase transitions

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

Acute Liver Failure Secondary to Hemophagocytic Lymphohistiocytosis during Pregnancy.

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of excessive immune activation that mimics and occurs with other systemic diseases. A 35-year-old female presented with signs of viral illness at 13 weeks of pregnancy and progressed to acute liver failure (ALF). We discuss the diagnosis of HLH and Kikuchi-Fujimoto (KF) lymphadenitis in the context of pregnancy and ALF. HLH may respond to comorbid disease-specific therapy, and more toxic treatment can be avoided

Exploring Entrepreneurship Education Effectiveness at British Universities – An Application of the World Café Method

Universities have made significant investments in entrepreneurship programs for decades, but the scope, relevance and usefulness of entrepreneurship education are still questioned. This study aims to explore the meaning of effectiveness as it relates to entrepreneurship education in a grounded and holistic sense, recognizing both the range of stakeholders involved in the design, delivery and experience of entrepreneurship education and the underlying complexity of the issue at hand. Two World Café events, a method designed to elicit grounded knowledge, were organized to seek insights from a diverse range of stakeholders. Results confirm and illustrate the complex nature of effectiveness in entrepreneurship education. The purpose of specific educational initiatives, diverse audiences’ expectations and contextual factors must be considered in any meaningful attempt at identifying effectiveness. Findings also revealed a consensus that effectiveness relates to creating a transformational process, which leads to a shift in attitudes towards entrepreneurship. This shift prepares students for careers that go beyond the launch of a new venture. The role of time lags in assessing effectiveness was also identified. We suggest an agenda for future research and practical implications

Axial Multicentric Osteosarcoma in an English Cocker Spaniel

No abstract available

Joint Strong and Weak Lensing Analysis of the Massive Cluster Field J0850+3604

We present a combined strong and weak lensing analysis of the J085007.6+360428 (J0850) field, which was selected by its high projected concentration of luminous red galaxies and contains the massive cluster Zwicky 1953. Using Subaru/Suprime-Cam $BVR_{c}I_{c}i^{\prime}z^{\prime}$ imaging and MMT/Hectospec spectroscopy, we first perform a weak lensing shear analysis to constrain the mass distribution in this field, including the cluster at $z = 0.3774$ and a smaller foreground halo at $z = 0.2713$. We then add a strong lensing constraint from a multiply-imaged galaxy in the imaging data with a photometric redshift of $z \approx 5.03$. Unlike previous cluster-scale lens analyses, our technique accounts for the full three-dimensional mass structure in the beam, including galaxies along the line of sight. In contrast with past cluster analyses that use only lensed image positions as constraints, we use the full surface brightness distribution of the images. This method predicts that the source galaxy crosses a lensing caustic such that one image is a highly-magnified "fold arc", which could be used to probe the source galaxy's structure at ultra-high spatial resolution ($< 30$ pc). We calculate the mass of the primary cluster to be $\mathrm{M_{vir}} = 2.93_{-0.65}^{+0.71} \times 10^{15}~\mathrm{M_{\odot}}$ with a concentration of $\mathrm{c_{vir}} = 3.46_{-0.59}^{+0.70}$, consistent with the mass-concentration relation of massive clusters at a similar redshift. The large mass of this cluster makes J0850 an excellent field for leveraging lensing magnification to search for high-redshift galaxies, competitive with and complementary to that of well-studied clusters such as the HST Frontier Fields.Comment: Accepted for publication in The Astrophysical Journal; 14 pages, 13 figures, 3 table

A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: Implications for H0H_0

Strong gravitational lensing provides an independent measurement of the Hubble parameter ($H_0$). One remaining systematic is a bias from the additional mass due to a galaxy group at the lens redshift or along the sightline. We quantify this bias for more than 20 strong lenses that have well-sampled sightline mass distributions, focusing on the convergence $\kappa$ and shear $\gamma$. In 23% of these fields, a lens group contributes a $\ge$1% convergence bias; in 57%, there is a similarly significant line-of-sight group. For the nine time delay lens systems, $H_0$ is overestimated by 11$^{+3}_{-2}$% on average when groups are ignored. In 67% of fields with total $\kappa \ge$ 0.01, line-of-sight groups contribute $\gtrsim 2\times$ more convergence than do lens groups, indicating that the lens group is not the only important mass. Lens environment affects the ratio of four (quad) to two (double) image systems; all seven quads have lens groups while only three of 10 doubles do, and the highest convergences due to lens groups are in quads. We calibrate the $\gamma$-$\kappa$ relation: $\log(\kappa_{\rm{tot}}) = (1.94 \pm 0.34) \log(\gamma_{\rm{tot}}) + (1.31 \pm 0.49)$ with a rms scatter of 0.34 dex. Shear, which, unlike convergence, can be measured directly from lensed images, can be a poor predictor of $\kappa$; for 19% of our fields, $\kappa$ is $\gtrsim 2\gamma$. Thus, accurate cosmology using strong gravitational lenses requires precise measurement and correction for all significant structures in each lens field.Comment: 34 pages, 11 figures, accepted for publication in Ap

The Evolution of the Interstellar Medium in Post-Starburst Galaxies

We derive dust masses ($M_{\rm dust}$) from the spectral energy distributions of 58 post-starburst galaxies (PSBs). There is an anticorrelation between specific dust mass ($M_{\rm dust}$/$M_{\star}$) and the time elapsed since the starburst ended, indicating that dust was either destroyed, expelled, or rendered undetectable over the $\sim$1 Gyr after the burst. The $M_{\rm dust}$/$M_{\star}$ depletion timescale, 205$^{+58}_{-37}$ Myr, is consistent with that of the CO-traced $M_{\rm H_2}/M_{\star}$, suggesting that dust and gas are altered via the same process. Extrapolating these trends leads to the $M_{\rm dust}/M_{\star}$ and $M_{\rm H_2}/M_{\star}$ values of early-type galaxies (ETGs) within 1-2 Gyr, a timescale consistent with the evolution of other PSB properties into ETGs. Comparing $M_{\rm dust}$ and $M_{\rm H_2}$ for PSBs yields a calibration, log $M_{\rm H_2}$ = 0.45 log $M_{\rm dust}$ + 6.02, that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, $\Sigma \rm SFR-\Sigma M_{\rm H_2}$. Over the first $\sim$200-300 Myr, the PSBs evolve down and off of the KS relation, as their star formation rate (SFR) decreases more rapidly than $M_{\rm H_2}$. Afterwards, $M_{\rm H_2}$ continues to decline whereas the SFR levels off. These trends suggest that the star-formation efficiency bottoms out at 10$^{-11}\ \rm yr^{-1}$ and will rise to ETG levels within 0.5-1.1 Gyr afterwards. The SFR decline after the burst is likely due to the absence of gas denser than the CO-traced H$_2$. The mechanism of the $M_{\rm dust}/M_{\star}$ and$M_{\rm H_2}/M_{\star}$ decline, whose timescale suggests active galactic nucleus (AGN) or low-ionization nuclear emission-line region (LINER) feedback, may also be preventing the large CO-traced molecular gas reservoirs from collapsing and forming denser star forming clouds.Comment: v1: 29 pages, 13 figures, to be published in ApJ. v2: Figure 6 and 7 fixed; more references adde