Relocation and analysis of the 2007 Nechako, B.C., seismic swarm: evidence for magmatic intrusion in the lower crust

On October 9th, 2007, a seismic swarm, known as the Nechako swarm, began in south-central British Columbia, approximately 20 kilometers west of the Nazko polygenetic cinder cone. After lasting for well over a month, seismic activity tapered off by November 21st, 2007. This study analyzes data from several temporary broadband seismometers deployed by the Geological Survey of Canada near the epicentral locations of initial events from the swarm. Over 4400 events were observed during this period, from which 1048 absolute locations were calculated, with depths ranging from 26-35 kilometers. All of the events recorded by the temporary seismometers were high frequency, volcano-tectonic earthquakes. A previous study by members of the Geological Survey of Canada reported a b-value (the slope of the magnitude-frequency relationship) of 1.9, indicating magmatic activity as the source for seismic unrest. Algorithmic double-difference programs HypoDD and TomoDD allowed for precise relocations of earthquake multiplets (earthquakes with similar waveforms) from the swarm, suggesting two distinct spatial and temporal pulses of seismic activity. The first pulse recorded by the temporary seismometers began on Oct. 21st, migrating southeast at a rate of 0.44 km/day from 26.5-28.3 km deep, until Oct. 29th. The second pulse began on Oct. 29th at a depth of 29-31 km, approximately 3 km to the southeast of the first pulse. No clear migration of events between the areas could be observed. On Nov. 2nd the first region of activity resumed seismic unrest. Both regions remained active for the remainder of the swarm. Distinct waveforms and hypocenters from spasmodic bursts (rapidly occurring events with overlapping waveforms) and earthquake multiplet clusters lend further credence to the simultaneous rupturing of the two regions. The proximity of high-frequency volcano-tectonic events to the crust-mantle boundary (approximately 30 km deep), the presence of spasmodic bursts, high b-value, and two distinct regions of simultaneous seismic activity provide strong evidence that the Nechako swarm was generated by the expansion and propagation of magma in the lower crust. Inverted, nearly identical waveforms are interpreted as originating from the brittle fracturing of solidified magma plugs, driven by the force of magma injection along a dike. From the evidence provided, I have concluded that the two spatially distinct regions of activity are representative of two large sills at the base of the crust, emplaced by crustal underplating, with branching dikes. The swarm was initiated by the brittle failure and fracturing of rock in the lower crust around these regions by either buoyantly rising magma in preexisting sills/dikes, or an injection of new magma from a mantle source

Supersingular Isogeny Diffie-Hellman with Legendre Form

SIDH is a key exchange algorithm proposed by Jao and De Feo that is conjectured to be post-quantum secure. The majority of work based on an SIDH framework uses elliptic curves in Montgomery form; this includes the original work by Jao, De Feo and Plût and the sate of the art implementation of SIKE. Elliptic curves in twisted Edwards form have also been used due to their efficient elliptic curve arithmetic, and complete Edwards curves have been used for their benefit of providing added security against side channel attacks. As far as we know, elliptic curves in Legendre form have not yet been explored for isogeny-based cryptography. Legendre form has the benefit of a very simple defining equation, and the simplest possible representation of the 2-torsion subgroup. In this work, we develop a new framework for constructing $2^a$-isogenies in SIDH using elliptic curves in Legendre form, and in doing so optimize Legendre curve arithmetic and $2$-isogeny computations on Legendre curves by avoiding any square root computations. We also describe an open problem which if solved would skip the strategy traversal altogether in SIDH through the Legendre curve framework

Efficiency Analysis of a Hall Thruster Operating with Krypton and Xenon

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76560/1/AIAA-19613-425.pd

The Sloan Digital Sky Survey Reverberation Mapping Project: Hα and Hβ reverberation measurements from first-year spectroscopy and photometry

Funding: UK Sciences and Technology Facilities Council STFC grant ST/M001296/1 (KH).We present reverberation mapping results from the first year of combined spectroscopic and photometric observations of the Sloan Digital Sky Survey Reverberation Mapping Project. We successfully recover reverberation time delays between the g+i band emission and the broad Hβ emission line for a total of 44 quasars, and for the broad Hα emission line in 18 quasars. Time delays are computed using the JAVELIN and CREAM software and the traditional interpolated cross-correlation function (ICCF): using well-defined criteria, we report measurements of 32 Hβ and 13 Hα lags with JAVELIN, 42 Hβ and 17 Hα lags with CREAM, and 16 Hβ and eight Hα lags with the ICCF. Lag values are generally consistent among the three methods, though we typically measure smaller uncertainties with JAVELIN and CREAM than with the ICCF, given the more physically motivated light curve interpolation and more robust statistical modeling of the former two methods. The median redshift of our Hβ-detected sample of quasars is 0.53, significantly higher than that of the previous reverberation mapping sample. We find that in most objects, the time delay of the Hα emission is consistent with or slightly longer than that of Hβ. We measure black hole masses using our measured time delays and line widths for these quasars. These black hole mass measurements are mostly consistent with expectations based on the local – relationship, and are also consistent with single-epoch black hole mass measurements. This work increases the current sample size of reverberation-mapped active galaxies by about two-thirds and represents the first large sample of reverberation mapping observations beyond the local universe (z < 0.3).PostprintPeer reviewe

Erratum to: Methods for evaluating medical tests and biomarkers

[This corrects the article DOI: 10.1186/s41512-016-0001-y.]

Evidence synthesis to inform model-based cost-effectiveness evaluations of diagnostic tests: a methodological systematic review of health technology assessments

Background: Evaluations of diagnostic tests are challenging because of the indirect nature of their impact on patient outcomes. Model-based health economic evaluations of tests allow different types of evidence from various sources to be incorporated and enable cost-effectiveness estimates to be made beyond the duration of available study data. To parameterize a health-economic model fully, all the ways a test impacts on patient health must be quantified, including but not limited to diagnostic test accuracy. Methods: We assessed all UK NIHR HTA reports published May 2009-July 2015. Reports were included if they evaluated a diagnostic test, included a model-based health economic evaluation and included a systematic review and meta-analysis of test accuracy. From each eligible report we extracted information on the following topics: 1) what evidence aside from test accuracy was searched for and synthesised, 2) which methods were used to synthesise test accuracy evidence and how did the results inform the economic model, 3) how/whether threshold effects were explored, 4) how the potential dependency between multiple tests in a pathway was accounted for, and 5) for evaluations of tests targeted at the primary care setting, how evidence from differing healthcare settings was incorporated. Results: The bivariate or HSROC model was implemented in 20/22 reports that met all inclusion criteria. Test accuracy data for health economic modelling was obtained from meta-analyses completely in four reports, partially in fourteen reports and not at all in four reports. Only 2/7 reports that used a quantitative test gave clear threshold recommendations. All 22 reports explored the effect of uncertainty in accuracy parameters but most of those that used multiple tests did not allow for dependence between test results. 7/22 tests were potentially suitable for primary care but the majority found limited evidence on test accuracy in primary care settings. Conclusions: The uptake of appropriate meta-analysis methods for synthesising evidence on diagnostic test accuracy in UK NIHR HTAs has improved in recent years. Future research should focus on other evidence requirements for cost-effectiveness assessment, threshold effects for quantitative tests and the impact of multiple diagnostic tests

Erratum to: Methods for evaluating medical tests and biomarkers

[This corrects the article DOI: 10.1186/s41512-016-0001-y.]

"Get off the track!" A song for emancipation, sung by The Hutchinsons, . . .

An illustrated sheet music cover for an abolitionist song composed by Jesse Hutchinson, Jr. The song is dedicated to antislavery editor Nathaniel Peabody Rogers, "As a mark of esteem for his intrepidity in the cause of Human Rights." It is illustrated with an allegory of the triumph of abolitionism. In a landscape a railroad car, "Immediate Emancipation," is drawn by a locomotive named "Liberator" and followed by another locomotive, the "Repealer," which pulls a second car "Liberty Votes and Ballot Boxes." The "Liberator" was the name of a prominent antislavery newspaper published in Boston by William Lloyd Garrison. "Repealer" probably refers to the Irish insurgent movement in support of the repeal of the Legislative Union, a cause with which many abolitionists in the United States were allied. Flags bearing the names of two other abolitionist publications, the "Herald of Freedom" and "American Standard" (i.e., Rogers's" National Anti-slavery Standard), fly from the "Emancipation" car. The trains approach a bend in the track, nearing a station where a number of people gather to welcome them. Beyond the station is a church. In the distance two other trains, one marked "Van" and the other "Clay," crash and their passengers flee. These allude to Democrat and Whig presidential hopefuls Martin Van Buren and Henry Clay. The reference to Van Buren suggests that the music-sheet appeared before the Democratic convention in May, when James K. Polk, not Van Buren, received the party's presidential nomination.Entered . . . 1844 by J. Hutchinson.Thayer & Co's. Lith Boston.Title appears as it is written on the item.Published in: American political prints, 1766-1876 / Bernard F. Reilly. Boston : G.K. Hall, 1991, entry 1844-52