Ultrasound imaging of cervical spine motion for extreme acceleration environments

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis. Vita.Includes bibliographical references (p. 52-55).Neck and back pain is one of the most common musculoskeletal complaints in personnel in variable acceleration environments such as astronauts and military pilots. Ultrasound is known for dynamic imaging and diagnostic workup of the axial and appendicular skeleton, but is not currently used to image the cervical spine, the injury of which may change the biomechanics of the cervical vertebrae, which CT and MRI (the current gold standard in cervical spine imaging) are poor at capturing. To validate ultrasound as a modality for imaging dynamic motion of the cervical spine several experiments were performed in static and dynamic human and animal (ovine) models: 1. Static analysis of ex-vivo ovine cervical spines imaged by ultrasound, MRI, and CT demonstrated that the imaging modality affected the measured intervertebral disc height (p<0.01); similar evaluation was done in-vivo in Emergency Department patients who received a CT scan as part of their clinical course that showed that ultrasound could fit into existing clinical workflows. 2. Dynamic analysis of isolated ex-vivo ovine cervical spinal segments intervertebral disc displacement with a mounted ultrasound probe demonstrated a measurement uncertainty of ± 0.2 mm and no bias at low frequency sinusoidal spinal displacement. A similar evaluation in-vivo with humans with an ultrasound probe mounted on a cervical-collar found a 0.8-1.3 mm amount of cervical spine distraction from the C4-5 Functional Spinal Unit. In human cadavers subjected to passive flexion and extension of the cervical spine, ultrasound measurements of the relative flexion/extension angles between consecutive cervical vertebrae were similar to fluoroscopy. 3. Ultrasound was able to record dynamic motion of the cervical spine in-vivo in running on a treadmill, during parabolic flight, and traveling over a rough road in a military vehicle. The ultrasound methods developed and tested in this thesis could provide an inexpensive, portable and safe technique that can identify and characterize cervical spine anatomy and pathology.Funding Acknowledgment: National Space Biomedical Research Institute, Army Research Office, Children's Hospital Orthopedic Surgery Foundationby Daniel Miller Buckland.Ph.D

Whale, whale, everywhere: increasing abundance of western South Atlantic humpback whales (Megaptera novaeangliae) in their wintering grounds

The western South Atlantic (WSA) humpback whale population inhabits the coast of Brazil during the breeding and calving season in winter and spring. This population was depleted to near extinction by whaling in the mid-twentieth century. Despite recent signs of recovery, increasing coastal and offshore development pose potential threats to these animals. Therefore, continuous monitoring is needed to assess population status and support conservation strategies. The aim of this work was to present ship-based line-transect estimates of abundance for humpback whales in their WSA breeding ground and to investigate potential changes in population size. Two cruises surveyed the coast of Brazil during August-September in 2008 and 2012. The area surveyed in 2008 corresponded to the currently recognized population breeding area; effort in 2012 was limited due to unfavorable weather conditions. WSA humpback whale population size in 2008 was estimated at 16,410 (CV = 0.228, 95% CI = 10,563–25,495) animals. In order to compare abundance between 2008 and 2012, estimates for the area between Salvador and Cabo Frio, which were consistently covered in the two years, were computed at 15,332 (CV = 0.243, 95% CI = 9,595–24,500) and 19,429 (CV = 0.101, 95% CI = 15,958–23,654) whales, respectively. The difference in the two estimates represents an increase of 26.7% in whale numbers in a 4-year period. The estimated abundance for 2008 is considered the most robust for the WSA humpback whale population because the ship survey conducted in that year minimized bias from various sources. Results presented here indicate that in 2008, the WSA humpback whale population was at least around 60% of its estimated pre-modern whaling abundance and that it may recover to its pre-exploitation size sooner than previously estimated.Publisher PDFPeer reviewe

ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations

The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we manage to collect observations for half of the post-discovery years (median), with data that have a median uncertainty less than one minute. In comparison with literature, the ephemerides generated by the project are more precise and less biased. More than 40\% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95\%), and also the identification of missing data. The dedicated ExoClock network effectively supports this task by contributing additional observations when a gap in the data is identified. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (TTVs - Transit Timing Variations) for a sample of 19 planets. All products, data, and codes used in this work are open and accessible to the wider scientific community.Comment: Recommended for publication to ApJS (reviewer's comments implemented). Main body: 13 pages, total: 77 pages, 7 figures, 7 tables. Data available at http://doi.org/10.17605/OSF.IO/P298

ExoClock Project. III. 450 New Exoplanet Ephemerides from Ground and Space Observations

The ExoClock project has been created to increase the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates, in order to produce a consistent catalog of reliable and precise ephemerides. This work presents a homogenous catalog of updated ephemerides for 450 planets, generated by the integration of ∼18,000 data points from multiple sources. These sources include observations from ground-based telescopes (the ExoClock network and the Exoplanet Transit Database), midtime values from the literature, and light curves from space telescopes (Kepler, K2, and TESS). With all the above, we manage to collect observations for half of the postdiscovery years (median), with data that have a median uncertainty less than 1 minute. In comparison with the literature, the ephemerides generated by the project are more precise and less biased. More than 40% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95%), and also the identification of missing data. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (transit-timing variations) for a sample of 19 planets. All the products, data, and codes used in this work are open and accessible to the wider scientific community

When a Waterhole is Full of Dung : An Illustration of the Importance of Environmental Evidence for Refining Archaeological Interpretation of Excavated Features

Prehistoric field systems sometimes encompass excavated, pit-like features which are difficult to classify due to the complex stratigraphies resulting from reuse, infilling and collapse. They are frequently classified as wells and watering holes, but other potential uses for excavated depressions are rarely cited. We argue the need for environmental archaeology in the interpretation of features of this nature, and present a case study from a Bronze Age site at Pode Hole, near Peterborough (UK), where fossil insect material clearly contradicts the archaeological interpretation. We present empirical evidence for a sealed context filled with dung which cannot be interpreted as a water source. This evidence strongly contrasts with other superficially similar features at the site.VISEADSEADBug

Adequacy of in-mission training to treat tibial shaft fractures in mars analogue testing

Abstract Long bone fractures are a concern in long-duration exploration missions (LDEM) where crew autonomy will exceed the current Low Earth Orbit paradigm. Current crew selection assumptions require extensive complete training and competency testing prior to flight for off-nominal situations. Analogue astronauts (n = 6) can be quickly trained to address a single fracture pattern and then competently perform the repair procedure. An easy-to-use external fixation (EZExFix) was employed to repair artificial tibial shaft fractures during an inhabited mission at the Mars Desert Research Station (Utah, USA). Bone repair safety zones were respected (23/24), participants achieved 79.2% repair success, and median completion time was 50.04 min. Just-in-time training in-mission was sufficient to become autonomous without pre-mission medical/surgical/mechanical education, regardless of learning conditions (p > 0.05). Similar techniques could be used in LDEM to increase astronauts’ autonomy in traumatic injury treatment and lower skill competency requirements used in crew selection