Quantifying Cross-scatter Contamination in Biplane Fluoroscopy Motion Analysis Systems

Biplane fluoroscopy is used for dynamic in vivo three-dimensional motion analysis of various joints of the body. Cross-scatter between the two fluoroscopy systems may limit tracking accuracy. This study measured the magnitude and effects of cross-scatter in biplane fluoroscopic images. Four cylindrical phantoms of 4-, 6-, 8-, and 10-in. diameter were imaged at varying kVp levels to determine the cross-scatter fraction and contrast-to-noise ratio (CNR). Monte Carlo simulations quantified the effect of the gantry angle on the cross-scatter fraction. A cadaver foot with implanted beads was also imaged. The effect of cross-scatter on marker-based tracking accuracy was investigated. Results demonstrated that the cross-scatter fraction varied from 0.15 for the 4-in. cylinder to 0.89 for the 10-in. cylinder when averaged across kVp. The average change in CNR due to cross-scatter ranged from 5% to 36% CNR decreases for the 4- and 10-in. cylinders, respectively. In simulations, the cross-scatter fraction increased with the gantry angle for the 8- and 10-in. cylinders. Cross-scatter significantly increased static-tracking error by 15%, 25%, and 38% for the 6-, 8-, and 10-in. phantoms, respectively, with no significant effect for the foot specimen. The results demonstrated submillimeter marker-based tracking for a range of phantom sizes, despite cross-scatter degradation

Formation and accretion history of terrestrial planets from runaway growth through to late time: implications for orbital eccentricity

Remnant planetesimals might have played an important role in reducing the orbital eccentricities of the terrestrial planets after their formation via giant impacts. However, the population and the size distribution of remnant planetesimals during and after the giant impact stage are unknown, because simulations of planetary accretion in the runaway growth and giant impact stages have been conducted independently. Here we report results of direct N-body simulations of the formation of terrestrial planets beginning with a compact planetesimal disk. The initial planetesimal disk has a total mass and angular momentum as observed for the terrestrial planets, and we vary the width (0.3 and 0.5AU) and the number of planetesimals (1000-5000). This initial configuration generally gives rise to three final planets of similar size, and sometimes a fourth small planet forms near the location of Mars. Since a sufficient number of planetesimals remains, even after the giant impact phase, the final orbital eccentricities are as small as those of the Earth and Venus.Comment: 36 pages, 9 figures, 1 table, Accepted in Ap

The Transnational Governance of Human Trafficking in Japan

Over the last two decades, governments and civil society groups have increasingly sought to govern human trafficking around the world, including by passing a major international Trafficking Protocol. Although the rise of human trafficking governance has been well-researched, much of this research has focussed on countries with weak economies and governance institutions. In these countries, foreign governments and NGOs can exert direct economic pressure to achieve policy changes, making it difficult to see how this governance works at an ideological level. For this dissertation, I therefore look at Japan—a country whose advanced economy and strong legal institutions make it easier to resist international pressure—in order to ask how transnational actors, ideas and networks influence the local governance of human trafficking. To answer this question, I spent over a year in Japan researching Japan’s response to human trafficking in sites across the country. The bulk of this fieldwork was semi-structured interviews with officials from government agencies, local police officers, the staff of NGOs and IGOs, and officials at foreign embassies. I also analysed a wide range of documentary evidence on Japan’s human trafficking situation and anti-trafficking policies. These included legal documents, policy directives, NGO reports, government pamphlets, media articles, international treaties and the US State Department’s Trafficking in Persons Report. Drawing on a Foucauldian conception of “governance,” this dissertation begins with a genealogy of human trafficking discourses. Internationally, I trace the evolution of human trafficking discourses from the anti-slavery campaigns of the 19th century through the battles over the legitimacy of sex work in mid-20th century, the securitisation of migration in the late-20th century and the shift back to “modern day slavery” in the 21st century. In Japan, I trace these discourses from caste slavery in the 7th century, bonded labourers in the medieval period, indentured sex workers in the early modern period, and child exploitation and migrant labour abuses in the 20th century. I use these histories both to explain the evolution of human trafficking governance in Japan and to show how this governance has been influenced by transnational actors. Finally, this dissertation looks at more recent attempts at domestic and transnational human trafficking governance in Japan, and explores why these attempts have (and have not) been successful. Based on this analysis, I argue that efforts at transnational human trafficking governance in Japan have been effective only when they were aligned with the priorities of local actors. As such, they have largely operated to magnify the influence of these actors, and contemporary human trafficking governance in Japan continues to reflect local ideas about migration and the legitimacy of sex work. However, I also note that when transnational actors have been successful in pushing their own anti-trafficking policies, these policies have sometimes harmed the very people they claimed to protect. This suggests that governments like Japan should work more closely with local civil society, rather than allowing transnational actors to be the ones defining human trafficking and how best to govern it

Three-manifolds with constant vector curvature

A connected Riemannian manifold M has constant vector curvature \epsilon, denoted by cvc(\epsilon), if every tangent vector v in TM lies in a 2-plane with sectional curvature \epsilon. By scaling the metric on M, we can always assume that \epsilon = -1, 0, or 1. When the sectional curvatures satisfy the additional bound that each sectional curvature is less than or equal to \epsilon, or that each sectional curvature is greater than or equal to \epsilon, we say that, \epsilon, is an extremal curvature. In this paper we study three-manifolds with constant vector curvature. Our main results show that finite volume cvc(\epsilon) three-manifolds with extremal curvature \epsilon are locally homogenous when \epsilon=-1 and admit a local product decomposition when \epsilon=0. As an application, we deduce a hyperbolic rank-rigidity theorem

Biplane Fluoroscopy for Hindfoot Motion Analysis during Gait: A Model-based Evaluation

The purpose of this study was to quantify the accuracy and precision of a biplane fluoroscopy system for model-based tracking of in vivo hindfoot motion during over-ground gait. Gait was simulated by manually manipulating a cadaver foot specimen through a biplane fluoroscopy system attached to a walkway. Three 1.6-mm diameter steel beads were implanted into the specimen to provide marker-based tracking measurements for comparison to model-based tracking. A CT scan was acquired to define a gold standard of implanted bead positions and to create 3D models for model-based tracking. Static and dynamic trials manipulating the specimen through the capture volume were performed. Marker-based tracking error was calculated relative to the gold standard implanted bead positions. The bias, precision, and root-mean-squared (RMS) error of model-based tracking was calculated relative to the marker-based measurements. The overall RMS error of the model-based tracking method averaged 0.43 ± 0.22 mm and 0.66 ± 0.43° for static and 0.59 ± 0.10 mm and 0.71 ± 0.12° for dynamic trials. The model-based tracking approach represents a non-invasive technique for accurately measuring dynamic hindfoot joint motion during in vivo, weight bearing conditions. The model-based tracking method is recommended for application on the basis of the study results

Structure and Kinematics of the Nearby Dwarf Galaxy UGCA 105

Owing to their shallow stellar potential, dwarf galaxies possess thick gas disks, which makes them good candidates for studies of the galactic vertical kinematical structure. We present 21 cm line observations of the isolated nearby dwarf irregular galaxy UGCA 105, taken with the Westerbork Synthesis Radio Telescope (WSRT), and analyse the geometry of its neutral hydrogen (HI) disk and its kinematics. The galaxy shows a fragmented HI distribution. It is more extended than the optical disk, and hence allows one to determine its kinematics out to very large galacto-centric distances. The HI kinematics and morphology are well-ordered and symmetric for an irregular galaxy. The HI is sufficiently extended to observe a substantial amount of differential rotation. Moreover, UGCA 105 shows strong signatures for the presence of a kinematically anomalous gas component. Performing tilted-ring modelling by use of the least-squares fitting routine TiRiFiC, we found that the HI disk of UGCA 105 has a moderately warped and diffuse outermost part. Probing a wide range of parameter combinations, we succeeded in modelling the data cube as a disk with a strong vertical gradient in rotation velocity ($\approx -60\,\rm km\,s^{-1}\,kpc^{-1}$), as well as vertically increasing inwards motion ($\approx -70\,\rm km\,s^{-1}\,kpc^{-1}$) within the radius of the stellar disk. The inferred radial gas inflow amounts to $0.06\,\rm M_\odot \rm yr^{-1}$, which is similar to the star formation rate of the galaxy. The observed kinematics are hence compatible with direct or indirect accretion from the intergalactic medium, an extreme backflow of material that has formerly been expelled from the disk, or a combination of both.Comment: 15 pages, 12 figures, accepted for publication in Astronomy & Astrophysic

Using Environmental DNA to Identify Habitat Requirements and Restoration Objectives for the Carolina Heelsplitter

The Carolina Heelsplitter (Lasmigona decorata) is a critically endangered freshwater mussel endemic to North and South Carolina. Because of its rarity, there is a deficit of information regarding the specific habitat requirements for colonization and persistence and where suitable habitat may exist. Understanding these requirements is essential for determining factors driving species decline and for guiding future management and restoration efforts. As part of an ongoing study, we developed a quantitative PCR assay to quantify the presence/absence of the Carolina Heelsplitter and a known host fish throughout the Upper Lynches River sub-basin in South Carolina. We will collect water samples during March of 2019, coinciding with the spring release of mussel larvae by gravid females. We will collect replicate water samples to account for imperfect detection and negative controls to monitor for potential contamination. We will investigate occupancy and detection probabilities as functions of environmental covariates, such as water chemistry, channel morphology, riparian characteristics, and land use attributes. Our preliminary results, which include controls and initial field samples, demonstrate the utility of eDNA as a highly sensitive survey tool, despite the extremely low density of the target species

A New Species of \u3ci\u3eGordius\u3c/i\u3e (Phylum Nematomorpha) from Terrestrial Habitats in North America

Freshwater hairworms (class Gordiida) are members of the phylum Nematomorpha that use terrestrial arthropods as definitive hosts but reside as free-living adult worms in rivers, lakes, or streams. The genus Gordius consists of 90 described species, of which three species were described from freshwater habitats in North America. In this paper we describe a new species of Gordius from terrestrial habitats in Oklahoma, Texas, and Louisiana, United States. Oddly, each year hundreds of adult free-living worms appear after bouts of heavy rain on streets, sidewalks, and lawns during the winter season, when terrestrial arthropod hosts are not active. The new species is described based on morphological characters of adults and nonadult stages including the egg strings, eggs, larvae, and cysts. Adult males have a unique row of bristles on the ventral inner side of each tail lobe and a circular pattern of bristles on the terminal end of each lobe, which distinguishes them from all other described North American species of Gordius. The egg string, larval, and cyst morphology of this new species conform to previous descriptions of non-adult hairworm stages for the genus Gordius. However, the eggs of this new species of hairworm are unique, as they contain an outer shell separated by distinct space from a thick inner membrane. The consistent occurrence of this gordiid in terrestrial habitats, along with its distinct egg morphology, suggests that this new species of hairworm has a terrestrial life cycle