Approximate Optimal Atmospheric Entry Trajectories

Approximate optimal atmospheric entry trajectories maximizing terminal function of velocity, heading angle, flight path angle, and altitud

The Lyman-alpha Forest at z~4: Keck HIRES Observations of Q 0000-26

This paper describes a study of the Lyman-alpha forest absorption clouds along the quasar sightline Q0000-26 (zem=4.1). The spectrum was obtained with the High Resolution Spectrometer on the 10m Keck telescope. We derive accurate H I column density and Doppler width distributions for the clouds from Voigt profile fitting. We also analyze simulated Lyman-alpha forest spectra of matching characteristics in order to gauge the effects of line blending/blanketing and noise in the data. The results are compared with similar studies at lower redshifts in order to study any possible evolution in the clouds' properties. We also estimate the mean intensity of the UV background at z=4 from an analysis of the proximity effect.Comment: plain TeX containing 23 PS pages, 3 PS tables, and 9 PS figures, ApJ, Dec 1, 1996 issue replacing an earlier version which contains an corrupted table

The Functional Morphology of the Hagfish Feeding Apparatus Dental Plate Complex

Hagfish are deep-sea craniates that have not evolved opposable jaws. Despite this, hagfish can “bite” forcefully, allowing them to utilize food sources ranging from marine worms to giant whale carcasses. Since hagfish do not have moveable jaws, their “bite” is created through a rasping motion of a tongue-like structure that contains a toothy dental plate. Hagfish protract and retract this plate using a feeding apparatus formed of elaborately arranged cartilages, muscles, and connective tissues. The rigid cartilages can be visualized using microCT scans, however, the soft tissues are often difficult to see. I solved this problem by imaging the soft tissues that join and actuate the rigid components using traditional histological techniques. I then created serial sections of multiple orientations to create a three-dimensional anatomical interpretation. This analysis indicated that the plates of the feeding apparatus are joined by connective tissue hinges and that the musculature is a multifunctional complex organized into antagonistic groups that allow the protraction and retraction of the dental plate

Multi-Scale Remote Sensing of Tornado Effects

To achieve risk-based engineered structural designs that provide safety for life and property from tornadoes, sufficient knowledge of tornado wind speeds and wind flow characteristics is needed. Currently, sufficient understanding of the magnitude, frequency, and velocity structure of tornado winds remain elusive. Direct measurements of tornado winds are rare and nearly impossible to acquire, and the pursuit of in situ wind measurements can be precarious, dangerous, and even necessitating the development of safer and more reliable means to understand tornado actions. Remote-sensing technologies including satellite, aerial, lidar, and photogrammetric platforms, have demonstrated an ever-increasing efficiency for collecting, storing, organizing, and communicating tornado hazards information at a multitude of geospatial scales. Current remote-sensing technologies enable wind-engineering researchers to examine tornado effects on the built environment at various spatial scales ranging from the overall path to the neighborhood, building, and ultimately member and/or connection level. Each spatial resolution contains a unique set of challenges for efficiency, ease, and cost of data acquisition and dissemination, as well as contributions to the body of knowledge that help engineers and atmospheric scientists better understand tornado wind speeds. This paper examines the use of remote sensing technologies at four scales in recent tornado investigations, demonstrating the challenges of data collection and processing at each level as well as the utility of the information gleaned from each level in advancing the understanding of tornado effects

Modelling pinniped abundance and distribution by combining counts at T terrestrial sites and in-water sightings

Pinnipeds are commonly monitored using aerial photographic surveys at land- or ice-based sites, where animals come ashore for resting, pupping, molting, and to avoid predators. Although these counts form the basis for monitoring population change over time, they do not provide information regarding where animals occur in the water, which is often of management and conservation interest. In this study, we developed a hierarchical model that links counts of pinnipeds at terrestrial sites to sightings-at-sea and estimates abundance, spatial distribution, and the proportion of time spent on land (attendance probability). The structure of the model also allows for the inclusion of predictors that may explain variation in ecological and observation processes. We applied the model to Steller sea lions (Eumetopias jubatus) in Glacier Bay, Alaska using counts of sea lions from aerial photographic surveys and opportunistic in-water sightings from vessel surveys. Glacier Bay provided an ideal test and application of the model because data are available on attendance probability based on long-term monitoring. We found that occurrence in the water was positively related to proximity to terrestrial sites, as would be expected for a species that engages in central-place foraging. The proportion of sea lions in attendance at terrestrial sites and overall abundance estimates were consistent with reports from the literature and monitoring programs. The model we describe has benefit and utility for park managers who wish to better understand the overlap between pinnipeds and visitors, and the framework that we present has potential for application across a variety of study systems and taxa

Multi-Scale Remote Sensing of Tornado Effects

To achieve risk-based engineered structural designs that provide safety for life and property from tornadoes, sufficient knowledge of tornado wind speeds and wind flow characteristics is needed. Currently, sufficient understanding of the magnitude, frequency, and velocity structure of tornado winds remain elusive. Direct measurements of tornado winds are rare and nearly impossible to acquire, and the pursuit of in situ wind measurements can be precarious, dangerous, and even necessitating the development of safer and more reliable means to understand tornado actions. Remote-sensing technologies including satellite, aerial, lidar, and photogrammetric platforms, have demonstrated an ever-increasing efficiency for collecting, storing, organizing, and communicating tornado hazards information at a multitude of geospatial scales. Current remote-sensing technologies enable wind-engineering researchers to examine tornado effects on the built environment at various spatial scales ranging from the overall path to the neighborhood, building, and ultimately member and/or connection level. Each spatial resolution contains a unique set of challenges for efficiency, ease, and cost of data acquisition and dissemination, as well as contributions to the body of knowledge that help engineers and atmospheric scientists better understand tornado wind speeds. This paper examines the use of remote sensing technologies at four scales in recent tornado investigations, demonstrating the challenges of data collection and processing at each level as well as the utility of the information gleaned from each level in advancing the understanding of tornado effects

Temperature and Kinematics of CIV Absorption Systems

We use Keck HIRES spectra of three intermediate redshift QSOs to study the physical state and kinematics of the individual components of CIV selected heavy element absorption systems. Fewer than 8 % of all CIV lines with column densities greater than 10^{12.5} cm^{-2} have Doppler parameters b < 6 km/s. A formal decomposition into thermal and non-thermal motion using the simultaneous presence of SiIV gives a mean thermal Doppler parameter b_{therm}(CIV) = 7.2 km/s, corresponding to a temperature of 38,000 K although temperatures possibly in excess of 300,000 K occur occasionally. We also find tentative evidence for a mild increase of temperature with HI column density. Non-thermal motions within components are typically small (< 10 km/s) for most systems, indicative of a quiescent environment. The two-point correlation function (TPCF) of CIV systems on scales up to 500 km/s suggests that there is more than one source of velocity dispersion. The shape of the TPCF can be understood if the CIV systems are caused by ensembles of objects with the kinematics of dwarf galaxies on a small scale, while following the Hubble flow on a larger scale. Individual high redshift CIV components may be the building blocks of future normal galaxies in a hierarchical structure formation scenario.Comment: submitted to the ApJ Letters, March 16, 1996 (in press); (13 Latex pages, 4 Postscript figures, and psfig.sty included

Limits to the 1/4 keV Extragalactic X-ray Background

We observed several nearby face-on spiral galaxies with the ROSAT PSPC. The apparent deficiency in soft X-ray surface brightness observed at the outer portion of their disks is consistent with the absorption of the extragalactic soft X-ray background by material associated with these galaxies, and allows us to place a lower limit on the intensity of this cosmologically important background. From the depth of the soft X-ray shadow observed in NGC 3184, a 95% confidence lower limit was derived to be $32 keV cm^{-2} s^{-1} keV^{-1}$ at 1/4 keV. This was obtained by assuming that there is no unresolved 1/4 keV X-ray emission from the outer region of the galaxy which may otherwise partially fill in the shadow: any such emission, or any unresolved structure in the absorbing gas, would imply a larger value. In the deepest exposure to date in this energy range, Hasinger et al. (1993) resolved about $30 keV cm^{-2} s^{-1} keV^{-1}$ at 1/4 keV into discrete sources; our current limit is therefore consistent with an extragalactic origin for all of these sources. Our results can also be directly compared with the corresponding upper limit derived from the ROSAT PSPC detection of soft X-ray shadows cast by high-latitude clouds in Ursa Major, $\simeq 65 keV cm^{-2} s^{-1} keV^{-1}$ at 1/4 keV. The lower and upper limits are only a factor of 2 apart, and begin to provide a reasonable measurement of the intensity of the 1/4 keV extragalactic X-ray background.Comment: 7 pages, no figures, a companion paper to the one titled "Diffuse Soft X-ray Emission from Several Nearby Spiral Galaxies" (astro-ph/9604128). To appear in September issue of ApJ (Vol. 468

Investigation of rapid remote sensing techniques for forensic wind analyses

Perishable damage data resulting from severe windstorms require efficient and rapid field collection techniques. Such datasets permit forensic damage investigations and characterization of civil infrastructure. Ultimately, observed structural damage serves as a proxy approach to estimate wind speeds for storms that include hurricanes, tornadoes, straight-line winds, etc. One of the more common methods to collect, preserve, and reconstruct three-dimensional damage scenes is the use of an unmanned aerial system (UAS), commonly known as a drone. Onboard photographic payloads permit scene reconstruction via structure-from-motion; however, such approaches often require direct site access and survey points for accurate results, which limit its efficiency. In this presentation, the use of UAS platforms with and without surveyed ground control points is investigated to understand the accuracy if site access is not possible. UAS datasets will be compared to lidar data of various structures collected following the 2017 Hurricane Harvey near Rockport, TX