Extension of Gutenberg-Richter Distribution to Mw -1.3, No Lower Limit in Sight

With twelve years of seismic data from TauTona Gold Mine, South Africa, we show that mining-induced earthquakes follow the Gutenberg-Richter relation with no scale break down to the completeness level of the catalog, at moment magnitude MW −1.3. Events recorded during relatively quiet hours in 2006 indicate that catalog detection limitations, not earthquake source physics, controlled the previously reported minimum magnitude in this mine. Within the Natural Earthquake Laboratory in South African Mines (NELSAM) experiment\u27s dense seismic array, earthquakes that exhibit shear failure at magnitudes as small as MW −3.9 are observed, but we find no evidence that MW −3.9 represents the minimum magnitude. In contrast to previous work, our results imply small nucleation zones and that earthquake processes in the mine can readily be scaled to those in either laboratory experiments or natural faults

Broadband Records of Earthquakes in Deep Gold Mines and a Comparison with Results from SAFOD, California

For one week during September 2007, we deployed a temporary network of field recorders and accelerometers at four sites within two deep, seismically active mines. The ground-motion data, recorded at 200 samples/sec, are well suited to determining source and ground-motion parameters for the mining-induced earthquakes within and adjacent to our network. Four earthquakes with magnitudes close to 2 were recorded with high signal/noise at all four sites. Analysis of seismic moments and peak velocities, in conjunction with the results of laboratory stick-slip friction experiments, were used to estimate source processes that are key to understanding source physics and to assessing underground seismic hazard. The maximum displacements on the rupture surfaces can be estimated from the parameter Rv, where v is the peak ground velocity at a given recording site, and R is the hypocentral distance. For each earthquake, the maximum slip and seismic moment can be combined with results from laboratory friction experiments to estimate the maximum slip rate within the rupture zone. Analysis of the four M 2 earthquakes recorded during our deployment and one of special interest recorded by the in-mine seismic network in 2004 revealed maximum slips ranging from 4 to 27 mm and maximum slip rates from 1.1 to 6:3 m=sec. Applying the same analyses to an M 2.1 earthquake within a cluster of repeating earthquakes near the San Andreas Fault Observatory at Depth site, California, yielded similar results for maximum slip and slip rate, 14 mm and 4:0 m=sec

Theory of the piezomagnetic effect in titanomagnetite-bearing rocks

The stress sensitivities S x and S R of susceptibility and remanence for titanomagnetite-bearing rocks are calculated in terms of magnetostriction constants λ 100 and λ 111 and anisotropy constants K 1 , K 2 of the magnetic minerals. S x and S R are represented by quite different algebraic expressions but happen to have comparable numerical values over the whole range of titanomagnetite compositions. Both increase strongly with titanium content. This leads to more optimistic calculations of tectonomagnetic effects than with the previously assumed stress sensitivity for pure magnetite.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43261/1/24_2004_Article_BF00875958.pd

Eruptions at Lone Star Geyser, Yellowstone National Park, USA: 1. Energetics and eruption dynamics

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 118 (2013): 4048–4062, doi:10.1002/jgrb.50251.Geysers provide a natural laboratory to study multiphase eruptive processes. We present results from a 4 day experiment at Lone Star Geyser in Yellowstone National Park, USA. We simultaneously measured water discharge, acoustic emissions, infrared intensity, and visible and infrared video to quantify the energetics and dynamics of eruptions, occurring approximately every 3 h. We define four phases in the eruption cycle (1) a 28±3 min phase with liquid and steam fountaining, with maximum jet velocities of 16–28 m s−1, steam mass fraction of less than ∼0.01. Intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction; (2) a 26±8 min posteruption relaxation phase with no discharge from the vent, infrared (IR), and acoustic power oscillations gliding between 30 and 40 s; (3) a 59±13 min recharge period during which the geyser is quiescent and progressively refills, and (4) a 69±14 min preplay period characterized by a series of 5–10 min long pulses of steam, small volumes of liquid water discharge, and 50–70 s flow oscillations. The erupted waters ascend from a 160–170°C reservoir, and the volume discharged during the entire eruptive cycle is 20.8±4.1 m3. Assuming isentropic expansion, we calculate a heat output from the geyser of 1.4–1.5 MW, which is <0.1% of the total heat output from Yellowstone Caldera.Support comes from NSF (L. Karlstrom, M. Manga), the USGS Volcano Hazards program (S. Hurwitz, F. Murphy, M.J.S. Johnston, and R.B. McCleskey), and WHOI (R. Sohn).2014-02-1

Cytotoxicity of Atriplex confertifolia

The search for cancer treatment continues to be a global effort. As part of this global effort, many natural products have been tested against cancer cell lines, mostly from tropically located plants. This study reports that extracts of Atriplex confertifolia (Torr. and Frem.) S. Watson (Chenopodiaceae), a native North American plant (also known as shadscale or saltbush), has significant bioactivity against human breast cancer cell lines MCF-7, MDA-MB 435, MDA-MB 231, and HeLa cells (cervical cancer cells). The bioactivity of A. confertifolia extracts on these cells lines was compared to an FDA-approved cancer drug (Onxol®) and an industry-standard leukocyte control cell line. Active portions of the extracts were found primarily in the polar fractions of the plant. A dose-response curve of the extracts displayed significant cell death similar to Onxol®. The plant extracts did not significantly inhibit the viability of the leukocyte cell line. In a timed study, over 90% of cell lines MDA-MB 435 and HeLa died after 24 hours. Cell death appears to result from apoptosis

Eruptions at Lone Star geyser, Yellowstone National Park, USA: 2. Constraints on subsurface dynamics

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 119 (2014): 8688–8707, doi:10.1002/2014JB011526.We use seismic, tilt, lidar, thermal, and gravity data from 32 consecutive eruption cycles of Lone Star geyser in Yellowstone National Park to identify key subsurface processes throughout the geyser's eruption cycle. Previously, we described measurements and analyses associated with the geyser's erupting jet dynamics. Here we show that seismicity is dominated by hydrothermal tremor (~5–40 Hz) attributed to the nucleation and/or collapse of vapor bubbles. Water discharge during eruption preplay triggers high-amplitude tremor pulses from a back azimuth aligned with the geyser cone, but during the rest of the eruption cycle it is shifted to the east-northeast. Moreover, ~4 min period ground surface displacements recur every 26 ± 8 min and are uncorrelated with the eruption cycle. Based on these observations, we conclude that (1) the dynamical behavior of the geyser is controlled by the thermo-mechanical coupling between the geyser conduit and a laterally offset reservoir periodically filled with a highly compressible two-phase mixture, (2) liquid and steam slugs periodically ascend into the shallow crust near the geyser system inducing detectable deformation, (3) eruptions occur when the pressure decrease associated with overflow from geyser conduit during preplay triggers an unstable feedback between vapor generation (cavitation) and mass discharge, and (4) flow choking at a constriction in the conduit arrests the runaway process and increases the saturated vapor pressure in the reservoir by a factor of ~10 during eruptions.Funding for USGS team members was provided by the USGS Volcano Hazards Program. R. Sohn's participation was supported by the WHOI Green Technology Program. M. Manga, L. Karlstrom and M. Rudolph did receive salary from the National Science Foundation to spend time on this project.2015-06-0

Revalidation and electronic cataract surgery audit: a Scottish survey on current practice and opinion

PURPOSE: To determine current knowledge and opinion on revalidation, and methods of cataract surgery audit in Scotland and to outline the current and future possibilities for electronic cataract surgery audit. METHODS: In 2010 we conducted a prospective, cross-sectional, Scottish-wide survey on revalidation knowledge and opinion, and cataract audit practice among all senior NHS ophthalmologists. Results were anonymised and recorded manually for analysis. RESULTS: In all, 61% of the ophthalmologists surveyed took part. Only 33% felt ready to take part in revalidation, whereas 76% felt they did not have adequate information about the process. Also, 71% did not feel revalidation would improve patient care, but 85% agreed that cataract surgery audit is essential for ophthalmic practice. In addition, 91% audit their cataract outcomes; 52% do so continuously. Further, 63% audit their subspecialist surgical results. Only 25% audit their cataract surgery practice electronically, and only 12% collect clinical data using a hospital PAS system. Funding and system incompatibility were the main reasons cited for the lack of electronic audit setup. Currently, eight separate hospital IT patient administration systems are used across 14 health boards in Scotland. CONCLUSION: Revalidation is set to commence in 2012. The Royal College of Ophthalmologists will use cataract outcome audit as a tool to ensure surgical competency for the process. Retrospective manual auditing of cataract outcome is time consuming, and can be avoided with an electronic system. Scottish ophthalmologists view revalidation with scepticism and appear to have inadequate knowledge of the process. However, they strongly agree with the concept of cataract surgery audit. The existing and future electronic applications that may support surgical audit are commercial electronic records, web-based applications, centrally funded software applications, and robust NHS connections between community and hospital

Darwin -— an experimental astronomy mission to search for extrasolar planets

As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument

Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy

Background A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets. Methods Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis. Results A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001). Conclusion We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty