1991 DA: An asteroid in a bizarre orbit

Asteroidal object 1991 DA has an orbit of high inclination, crossing the planets from Mars to Uranus. This is unique for an asteroid, but not unusual for a comet of the Halley-type: it therefore seems likely that 1991 DA is an extinct or dormant comet. Previous CCD imaging has shown no indication of a coma; spectroscopic observations of 1991 DA which lack any evidence of strong comet-like emissions are reported. Numerical integrations of the orbit of this object were performed which show that is has been remarkably stable for the past approximately 20,000 yr, but chaotic before that. This may allow a new estimate to be made of the physical lifetimes of comets

Elements of Employment Related Disclosure of Disability after Brain Injury

Few studies have examined the elements of disclosing a disability in the workplace. Those few studies had a primary focus on reasonable accommodations (RA) where the disclosure process was either secondary or tertiary to the study. Further, there have been no studies to date which have examined elements of disclosure for individuals with brain injury (BI). Disclosure of disability is a crucial first step in the request process for a reasonable accommodation in the workplace and is required by the ADA for individuals requesting job related accommodations. This study examined the (a) experiences of work-related disability disclosure for individuals with BI, (b) the injury, demographic and other factors associated with the decision to disclose a disability at work, and (c) employment-related outcomes associated with disclosure. The primary goal of the current study is to describe the population of people with brain injury who disclose their disability in the workplace and to make inferences about the contributing factors involved in the disclosure process. The study used a cross-sectional survey methods research design. The study consisted of 200 individuals recruited from an online survey hosted on the Brain Injury Association of America's website. Of these participants, 144 (74.6%) disclosed their disability on at least one job and 91 (45%) were currently working. Level of education (X2 =11.945, 3, p=.008), self-efficacy score (F=7.52; p=.007) and time between injury and current age (F=4.56; p=.034) were significantly related to disclosure. Logistic regression analyses were used to examine the combined effects of several predictor variables with disclosure. In this analysis, only time since injury and self-efficacy (SE) scores were significant, where higher SE scores increased the odds of disclosure, and time since injury decreases the odds of disclosure (the more recent the injury, the more likely the individual was to disclose)

X-Ray Analysis of Some Hunterburnine and Santonin Derivatives

X-ray studies have been carried out on crystals of heavy-atom derivatives of naturally-occurring organic compounds and related photo-irradiation products. Four structures have been successfully solved: the alkaloid hunterburnine, the sesquiterpenoid santonin and its photo-irradiation product isophoto-a-santonic lactone, and the colouring material ergoflavin. Attempts to solve the structure of toxisterol A2, a photo-irradiation product of the steroid ergosterol, have proved fruitless. The elucidation of the structure of hunterburnine resulted from a straightforward application of the heavy atom technique to hunterburnine methiodide and the complete structure was assigned with certainty from the fifth three-dimensional Fourier synthesis. Subsequent refinement reduced the discrepancy, R, to 15.4% Hunterburnine represents a new class of indole alkaloid. The analysis of bromodihydroisophoto-a-santonic lactone acetate was undertaken to define the stereochemistry of the parent molecule. The analysis was hindered in the early stages by spurious symmetry which was eventually overcome with the aid of chemical knowledge of the structure. The structure has been refined and the final value of R is 12.9%. The analysis has established the relative stereochemistry of isophoto-alpha-antonic lactone. The configuration of the methyl group on the lactone ring of isophoto-alpha-santonic lactone is opposite to that generally accepted, Implying that the assignation of the stereochemistry of the corresponding methyl group in santonin itself was in error. Hence an analysis of the heavy-atom derivative 2-bromo-a-santonin was undertaken. In spite of spurious symmetry, the structure was solved and refined to give a discrepancy of 15.2%. The analysis has confirmed the revised configuration of the controversial methyl group in santonin. Inter- and intra-molecular dimensions in these three structures are in reasonable agreement with accepted values. The structure and stereochemistry of tetramethyl ergoflavin di-p-iodobenzoate have been established and refinement of the structure is in progress. Molecular dimensions have not been discussed, but the gross molecular structure is in agreement with chemical evidence with the exception of the assignment of hydroxyl and phenolic groupings. This project was studied in conjunction with A. T. McPhail and J. V. Silverton. The final chapter of this thesis describes an attempt to solve the structure of toxisterol A2 4-iodo-3-nitrobensoate which crystallises in the monoclinic system with space group P2 1. The heavy-atom positions have been located, but it has not been possible to allocate additional atomic sites from three-dimensional Fourier maps or a three-dimensional superimposed Patterson synthesis

An Accurate and Dynamic Computer Graphics Muscle Model

A computer based musculo-skeletal model was developed at the University in the departments of Mechanical and Biomedical Engineering. This model accurately represents human shoulder kinematics. The result of this model is the graphical display of bones moving through an appropriate range of motion based on inputs of EMGs and external forces. The need existed to incorporate a geometric muscle model in the larger musculo-skeletal model. Previous muscle models did not accurately represent muscle geometries, nor did they account for the kinematics of tendons. This thesis covers the creation of a new muscle model for use in the above musculo-skeletal model. This muscle model was based on anatomical data from the Visible Human Project (VHP) cadaver study. Two-dimensional digital images from the VHP were analyzed and reconstructed to recreate the three-dimensional muscle geometries. The recreated geometries were smoothed, reduced, and sliced to form data files defining the surfaces of each muscle. The muscle modeling function opened these files during run-time and recreated the muscle surface. The modeling function applied constant volume limitations to the muscle and constant geometry limitations to the tendons

Sodium-dependent transport of phosphate in neuronal and related cells

AbstractSodium-dependent phosphate entry into neuronal cells was demonstrated in synaptic plasma membrane vesicles and synaptosomes prepared from rat brains, in PC12 cells and in primary culture of pituitary cells. The extent of the sodium-dependent phosphate transport in the synaptic plasma membrane preparation, at [Na]out=110 mM and [Pi]out=0.1 mM, varied between 0.28 to 1.02 nmol phosphate/mg membrane protein/min. In pituitary cells the value was only about 0.05 nmol Pi/mg protein/min. In PC12 cells the activity increased from 0.0085 to 0.26 nmol Pi/mg protein/min in the transit from undifferentiated to differentiated cells. The dependence of phosphate on sodium concentrations fits a model in which two sodium ions are required to transfer the phosphate into the cells with a K[Na]0.5 of 43 mM. The Km for the phosphate transport in the synaptic plasma membrane preparations was between 0.1 and 0.45 mM. It is concluded that sodium-driven active transport of phosphate is a ubiquitous activity in various types of neuronal cells

Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation

The extended Kepler mission, K2, is now providing photometry of new fields every three months in a search for transiting planets. In a recent study, Foreman-Mackey and collaborators presented a list of 36 planet candidates orbiting 31 stars in K2 Campaign 1. In this contribution, we present stellar and planetary properties for all systems. We combine ground-based seeing-limited survey data and adaptive optics imaging with an automated transit analysis scheme to validate 21 candidates as planets, 17 for the first time, and identify 6 candidates as likely false positives. Of particular interest is K2-18 (EPIC 201912552), a bright (K=8.9) M2.8 dwarf hosting a 2.23 \pm 0.25 R_Earth planet with T_eq = 272 \pm 15 K and an orbital period of 33 days. We also present two new open-source software packages which enable this analysis. The first, isochrones, is a flexible tool for fitting theoretical stellar models to observational data to determine stellar properties using a nested sampling scheme to capture the multimodal nature of the posterior distributions of the physical parameters of stars that may plausibly be evolved. The second is vespa, a new general-purpose procedure to calculate false positive probabilities and statistically validate transiting exoplanets.Comment: 17 pages, 5 figures, 5 tables, accepted for publication in the Astrophysical Journal. Updated to closely reflect published version in ApJ (2015, 809, 25