Impacts of predation risk and development on susceptibility of North American anurans to ranaviruses

For over three decades, amphibian populations have been declining across the globe. Emerging infectious diseases are responsible for some of these declines. Ranaviruses have caused die-offs in wild amphibian populations on 4 continents, in 5 Canadian provinces, and in over 25 U.S. states. In order to understand host-pathogen dynamics, it is critical to establish baseline information on species susceptibility and the effects of natural stressors. The goal of my thesis research was to quantify the effects of anuran development and exposure to invertebrate predators on species-specific susceptibility to ranavirus. My experiments were designed in factorial arrangements, and consisted of exposure to ranavirus during different developmental stages or with and without predator cues in a controlled environment. I found that exposure to invertebrate predator cues did not increase susceptibility to ranavirus for 4 anuran species tested. Susceptibility differed among embryo, hatchling, larval and metamorph stages, but trends differed among species and did not follow predictions based on Xenopus laevis immune function. Low susceptibility during the embryo stage was the only consistent development result among species, perhaps owing to protective qualities of the vitelline membrane or mucoidal capsules surrounding the embryo. Across 7 anuran species tested, mean mortality rates ranged from 5 – 100%, with Lithobates sylvaticus and Scaphiopus holbrookii most susceptible. I found that infection rates and viral load were correlated with mortality rates, thus these variables are good indicators of susceptibility to ranavirus. My results indicate that ranaviruses can cause catastrophic natural mortality in some anuran species, and likely play a significant role in local population dynamics. For highly susceptible species, ranaviruses could cause local extirpations that lead to species declines. More information is needed on the role of natural (e.g., co-infection, competition) and anthropogenic stressors in driving ranavirus epizootic events. I encourage natural resource agencies to initiate ranavirus surveillance programs, especially for rare species and fragmented populations. Future studies should take an immunogenetic approach to identifying mechanisms driving susceptibility. Identifying mechanisms associated with ranavirus emergence is fundamental to developing science-based conservation strategies

The Effect of CEO IT Expertise on the Information Environment: Evidence from Management Earnings Forecasts

Firms depend on information technology to provide high quality internal information, but prior research suggests that IT is underutilized (Venkatesh and Bala 2008). Therefore, using a sample of firms with equivalent levels of technology in their information systems, I investigate whether firms that employ CEOs with IT expertise make forecasts that are more accurate. I argue that CEOs with IT expertise are more likely to encourage the utilization of IT in making earnings forecasts, thus increasing the accuracy of the forecasts. This argument is supported by prior research that suggests that people are more likely to utilize technology if they have more experience with IT (Venkatesh et al. 2012). This research suggests that executives with IT experience are more likely to utilize IT because they perceive it as easy to use. Overall, I find that CEOs with IT expertise make forecasts that are more accurate. In additional tests, I also find that CEOs with IT expertise do not manage earnings to maintain accuracy. Finally, I find that analysts are more likely to rely on information provided by CEOs with IT expertise. Additionally, analysts benefit from the high quality information provided by CEOs with IT expertise because analysts that revise their forecasts following a forecast issued by a CEO with IT expertise make forecasts that are more accurate

Do the Roles of the CEO and CFO Differ when it comes to Data Security Breaches?

Using a sample of S&P 1500 firms from 2005-2013, we investigate the independent relationships of Chief Executive Officer (CEO) IT expertise, Chief Financial Officer (CFO) IT expertise, and board level technology committees with data security breaches. Overall, our results indicate that firms that either employ a CEO with IT expertise or implement a technology committee are more likely to detect and report breaches. Further, firms that employ a CFO with IT expertise are less likely to report a breach, suggesting that these firms are better at preventing breaches. The aggregate findings build on the extant corporate governance and risk management literatures

Building the Evryscope: Hardware Design and Performance

The Evryscope is a telescope array designed to open a new parameter space in optical astronomy, detecting short timescale events across extremely large sky areas simultaneously. The system consists of a 780 MPix 22-camera array with an 8150 sq. deg. field of view, 13" per pixel sampling, and the ability to detect objects down to Mg=16 in each 2 minute dark-sky exposure. The Evryscope, covering 18,400 sq.deg. with hours of high-cadence exposure time each night, is designed to find the rare events that require all-sky monitoring, including transiting exoplanets around exotic stars like white dwarfs and hot subdwarfs, stellar activity of all types within our galaxy, nearby supernovae, and other transient events such as gamma ray bursts and gravitational-wave electromagnetic counterparts. The system averages 5000 images per night with ~300,000 sources per image, and to date has taken over 3.0M images, totaling 250TB of raw data. The resulting light curve database has light curves for 9.3M targets, averaging 32,600 epochs per target through 2018. This paper summarizes the hardware and performance of the Evryscope, including the lessons learned during telescope design, electronics design, a procedure for the precision polar alignment of mounts for Evryscope-like systems, robotic control and operations, and safety and performance-optimization systems. We measure the on-sky performance of the Evryscope, discuss its data-analysis pipelines, and present some example variable star and eclipsing binary discoveries from the telescope. We also discuss new discoveries of very rare objects including 2 hot subdwarf eclipsing binaries with late M-dwarf secondaries (HW Vir systems), 2 white dwarf / hot subdwarf short-period binaries, and 4 hot subdwarf reflection binaries. We conclude with the status of our transit surveys, M-dwarf flare survey, and transient detection.Comment: 24 pages, 24 figures, accepted PAS

EvryFlare II: Rotation Periods of the Cool Flare Stars in TESS Across Half the Southern Sky

We measure rotation periods and sinusoidal amplitudes in Evryscope light curves for 122 two-minute K5-M4 TESS targets selected for strong flaring. The Evryscope array of telescopes has observed all bright nearby stars in the South, producing two-minute cadence light curves since 2016. Long-term, high-cadence observations of rotating flare stars probe the complex relationship between stellar rotation, starspots, and superflares. We detect periods from 0.3487 to 104 d, and observe amplitudes from 0.008 to 0.216 g' mag. We find the Evryscope amplitudes are larger than those in TESS with the effect correlated to stellar mass (p-value=0.01). We compute the Rossby number (Ro), and find our sample selected for flaring has twice as many intermediate rotators (0.040.44) rotators; this may be astrophysical or a result of period-detection sensitivity. We discover 30 fast, 59 intermediate, and 33 slow rotators. We measure a median starspot coverage of 13% of the stellar hemisphere and constrain the minimum magnetic field strength consistent with our flare energies and spot coverage to be 500 G, with later-type stars exhibiting lower values than earlier-types. We observe a possible change in superflare rates at intermediate periods. However, we do not conclusively confirm the increased activity of intermediate rotators seen in previous studies. We split all rotators at Ro~0.2 into Prot10 d bins to confirm short-period rotators exhibit higher superflare rates, larger flare energies, and higher starspot coverage than do long-period rotators, at p-values of 3.2 X 10^-5, 1.0 X 10^-5, and 0.01, respectively.Comment: 16 pages, 8 figures, 3 tables. Ancillary machine-readable files included. Accepted for publication in ApJ (proofs submitted). Includes significant new material, including starspot color that depends on stellar mass, more rotation periods, potential changes in activity during spin-down, and examples of binary rotator