Evaluation of a high-torque backlash-free roller actuator

The results are presented of a test program that evaluated the stiffness, accuracy, torque ripple, frictional losses, and torque holding capability of a 16:1 ratio, 430 N-m (320 ft-lb) planetary roller drive for a potential space vehicle actuator application. The drive's planet roller supporting structure and bearings were found to be the largest contributors to overall drive compliance, accounting for more than half of the total. In comparison, the traction roller contacts themselves contributed only 9 percent of the drive's compliance based on an experimentally verified stiffness model. The drive exhibited no backlash although 8 arc sec of hysteresis deflection were recorded due to microcreep within the contact under torque load. Because of these load-dependent displacements, some form of feedback control would be required for arc second positioning applications. Torque ripple tests showed the drive to be extremely smooth, actually providing some damping of input torsional oscillations. The drive also demonstrated the ability to hold static torque with drifts of 7 arc sec or less over a 24 hr period at 35 percent of full load

Studies on starches: with particular reference to the characterization or their amylose and amylopeotin components; and analyses or some starch-containing materials

Starch is one of the most important natural products. It finds many industrial uses and applications, and, in different forms, is used throughout the world as a staple item of the human diet. Consequently, the structure and properties of starch have deservedly formed the subject of extensive investigations both by chemists and bio-chemists. Because of the inherent difficulties in the many problems which arose, and the continual need for development of new techniques, progress prior to 1925 was slow and uncertain. However, the subsequent elucidation of the precise structural configurations of the simpler sugars e.g. glucose, maltose and cellobiose, gave a firm foundation for future work, and steady progress ensued. One of the most important advances was the realisation of the apparent inhomogeneity of starch; this was followed in 1941 by the first quantitative fractionation into simpler components. As a result, the highly polymeric nature and main structural features of the molecule are now well estab¬ lished. In general, starches can be separated into two distinct entities, both of which are high polymers of α-D-glucopyranose units joined by α-1:4-glycosidic linkages: (a) Amylose - a mixture of very long, essentially inbranched, chains of these units. (b) Arnylopectin - a mixture of much shorter, highly branched chains of these units, the inter-chain, or branching, linkages being essentially α-l;6. Yet many problems still remain. Some are concerned with the clarification of controversial issues on which the present experimental evidence, as reported by various workers, is either at variance or considered to be inconclusive; the majority, however, are concerned with the fundamentally important details of fine structure and the molecular size and shape of the starch components. It is now accepted that there is little prospect of progress on these particular problems unless full use is made by the carbohydrate chemist of physical and enzymic methods to supplement purely chemical approaches. When the researches reported in this thesis were begun, it was apparent that, before the established physical techniques used in polymer chemistry for the determination of molecular size and shape could be profitably applied, work on the following topics was an essential preliminary in order that the materials to be studied could be adequately and accurately characterized:- (1) The development of a differential potentiometric iodine titration technique for the determination of the % amylose in starches and their fractionated components, and for the possible characterization of other a-1:4-glucosans. It was desirable that the apparatus should be considerably more sensitive and accurate than any of those previously reported, yet also be capable of simple operation as a routine analytical method. (2) A study of the oxidation of starches by the periodate ion in view of the low quoted percentage accuracy of the technique, and the then existing lack of agreement in the literature on the following points; (a) conditions for the quantitative estimation of the formic acid released, (b) the length of time required for complete oxidation, and the possibility of over-oxidation, (c) the presence of intact glucose residues after oxidation, suggesting that inter-chain linkages other than 1:6 existed in amylopectin. (3) A study of the effect of the presence of contaminating protein on results obtained by use of the potentiometric iodine titration and periodate oxidation techniques. (4) The preparation, and purification, of starches from several botanical sources which had not previously been studied, so that the use at any stage of industrial samples of unknown origin, treatment, and history could be avoided. By preparation of the starches under the mildest possible conditions, so as to minimise degradation, these same samples could later be used for physico-chemical studies of molecular size and shape. The opportunity was taken, after the extraction of each starch, to apply a graded series of extractions to the residual plant material; the fractions isolated were analysed for protein, ash, and uronic acid content, and the polysaccharide content was investigated by chromatographic analyses of the sugars liberated on hydrolysis

PTSD/SUD in Individuals with Physical Disabilities: Identifying Problems and Promising Interventions

Co-occurring posttraumatic stress disorder (PTSD) and substance use disorder (SUD) is common, affects multiple domains of functioning, and presents complex challenges to recovery. Initial research indicates that individuals with physical disabilities experience higher rates of lifetime trauma and PTSD, and exhibit more severe SUD compared to non-disabled individuals. To expand upon these initial findings, we conducted a series of two studies on PTSD and SUD among individuals with physical disabilities

Stability Walls in Heterotic Theories

We study the sub-structure of the heterotic Kahler moduli space due to the presence of non-Abelian internal gauge fields from the perspective of the four-dimensional effective theory. Internal gauge fields can be supersymmetric in some regions of the Kahler moduli space but break supersymmetry in others. In the context of the four-dimensional theory, we investigate what happens when the Kahler moduli are changed from the supersymmetric to the non-supersymmetric region. Our results provide a low-energy description of supersymmetry breaking by internal gauge fields as well as a physical picture for the mathematical notion of bundle stability. Specifically, we find that at the transition between the two regions an additional anomalous U(1) symmetry appears under which some of the states in the low-energy theory acquire charges. We compute the associated D-term contribution to the four-dimensional potential which contains a Kahler-moduli dependent Fayet-Iliopoulos term and contributions from the charged states. We show that this D-term correctly reproduces the expected physics. Several mathematical conclusions concerning vector bundle stability are drawn from our arguments. We also discuss possible physical applications of our results to heterotic model building and moduli stabilization.Comment: 37 pages, 4 figure

Quiver Structure of Heterotic Moduli

We analyse the vector bundle moduli arising from generic heterotic compactifications from the point of view of quiver representations. Phenomena such as stability walls, crossing between chambers of supersymmetry, splitting of non-Abelian bundles and dynamic generation of D-terms are succinctly encoded into finite quivers. By studying the Poincar\'e polynomial of the quiver moduli space using the Reineke formula, we can learn about such useful concepts as Donaldson-Thomas invariants, instanton transitions and supersymmetry breaking.Comment: 38 pages, 5 figures, 1 tabl

Heterotic Models from Vector Bundles on Toric Calabi-Yau Manifolds

We systematically approach the construction of heterotic E_8 X E_8 Calabi-Yau models, based on compact Calabi-Yau three-folds arising from toric geometry and vector bundles on these manifolds. We focus on a simple class of 101 such three-folds with smooth ambient spaces, on which we perform an exhaustive scan and find all positive monad bundles with SU(N), N=3,4,5 structure groups, subject to the heterotic anomaly cancellation constraint. We find that anomaly-free positive monads exist on only 11 of these toric three-folds with a total number of bundles of about 2000. Only 21 of these models, all of them on three-folds realizable as hypersurfaces in products of projective spaces, allow for three families of quarks and leptons. We also perform a preliminary scan over the much larger class of semi-positive monads which leads to about 44000 bundles with 280 of them satisfying the three-family constraint. These 280 models provide a starting point for heterotic model building based on toric three-folds.Comment: 41 pages, 5 figures. A table modified and a table adde

Numerical Hermitian Yang-Mills Connections and Kahler Cone Substructure

We further develop the numerical algorithm for computing the gauge connection of slope-stable holomorphic vector bundles on Calabi-Yau manifolds. In particular, recent work on the generalized Donaldson algorithm is extended to bundles with Kahler cone substructure on manifolds with h^{1,1}>1. Since the computation depends only on a one-dimensional ray in the Kahler moduli space, it can probe slope-stability regardless of the size of h^{1,1}. Suitably normalized error measures are introduced to quantitatively compare results for different directions in Kahler moduli space. A significantly improved numerical integration procedure based on adaptive refinements is described and implemented. Finally, an efficient numerical check is proposed for determining whether or not a vector bundle is slope-stable without computing its full connection.Comment: 38 pages, 10 figure

Piloting Signs of Safety : A Deaf-Accessible Toolkit for Trauma and Addiction

The Deaf community - a minority group of 500,000 Americans who use American Sign Language (ASL) - experiences trauma and addiction at rates double to the general population. Yet, there are no evidence-based treatments that have been evaluated to treat trauma, addiction, or other behavioral health conditions among Deaf people. Current evidence-based treatments fail to meet the needs of Deaf clients. One example is Seeking Safety, a well-validated therapy for people recovering from trauma and addiction. Seeking Safety includes a therapist guide and client handouts for 25 therapy sessions, each teaching clients a safe coping skill. When Seeking Safety was used with Deaf clients, unique barriers were revealed with regard to the client materials: they were presented in complex English instead of ASL, nor sensitive to Deaf people’s culture, social norms, and history of oppression. To address these barriers, Dr. Anderson assembled a team of Deaf and hearing researchers, clinicians, filmmakers, actors, artists, and Deaf people in recovery to develop Signs of Safety, a Deaf-accessible toolkit to be used with Seeking Safety. Signs of Safety is comprised of a therapist companion guide and population-specific client materials, including visual handouts and ASL teaching stories on digital video, which present key learning points via an “educational soap opera.” Dr. Anderson is currently leading a pilot study of Signs of Safety. Preliminary results show that participants are reporting symptom reduction from baseline to follow-up and high levels of satisfaction with the model, giving us the confidence to further pursue this line of research