18,315 research outputs found

    Akterations/corrections to the BRASS Program

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    Corrections applied to statistical programs contained in two subroutines of the Bed Rest Analysis Software System (BRASS) are summarized. Two subroutines independently calculate significant values within the BRASS program

    Space-flight simulations of calcium metabolism using a mathematical model of calcium regulation

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    The results of a series of simulation studies of calcium matabolic changes which have been recorded during human exposure to bed rest and space flight are presented. Space flight and bed rest data demonstrate losses of total body calcium during exposure to hypogravic environments. These losses are evidenced by higher than normal rates of urine calcium excretion and by negative calcium balances. In addition, intestinal absorption rates and bone mineral content are assumed to decrease. The bed rest and space flight simulations were executed on a mathematical model of the calcium metabolic system. The purpose of the simulations is to theoretically test hypotheses and predict system responses which are occurring during given experimental stresses. In this case, hypogravity occurs through the comparison of simulation and experimental data and through the analysis of model structure and system responses. The model reliably simulates the responses of selected bed rest and space flight parameters. When experimental data are available, the simulated skeletal responses and regulatory factors involved in the responses agree with space flight data collected on rodents. In addition, areas within the model that need improvement are identified

    An investigation of the impact of ensemble interrelationship on performances of improvised music through practice research

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    In this thesis I present my investigation into the ways in which the creative and social relationships I have developed with long-term collaborators alter or affect the musical decisions I make in my performances of Improvised Music. The aim of the investigation has been to deepen the understanding of my musical and relational processes as a trombonist through the examination of my artistic practice, which is formed by experiences in range of genres such as Jazz and contemporary music, with a current specialty in Improvised Music performance. By creating an interpretative framework from the theoretical and analytical processes used in music therapy practice, I have introduced a tangible set of concepts that can interpret my Improvised Music performance processes and establish objective perspectives of subjective musical experiences. Chapter one is concerned with recent debates in Improvised Music and music therapy. Particular reference is made to literature that considers interplay between performers. Chapter two focuses on my individual artistic practice and examines the influence of five trombone players from Jazz and Improvised Music performance on my praxis. A recording of one of my solo trombone performances accompanies this section. It concludes with a discussion on my process of making tacit knowledge of Improvised Music performance tangible and explicit and the abstruse nature of subjective feeling states when performing improvisation. This concludes part one of the thesis. The second part of the thesis is concerned with the development and application of concepts and their outcomes. In chapter three, I present frameworks drawn from concepts in music therapy practice. Musical material from my work with long standing collaborators Steve Beresford, John Edwards and Mark Sanders form the basis of three case studies presented in chapter four. Recordings of trio and quartet pieces accompany case study one and two. A recording of a duo with myself and Mark Sanders accompanies case three. In the conclusion, I provide a summary of the research processes, frameworks for analysis and their outcomes. My quartet record All Will Be Said, All To Do Again, which was recorded in the period of this research, forms part three of the study and is the basis for two of three pieces in the aforementioned case studies in chapter four. Part three also includes a live performance of the quartet featuring myself and the musicians featured in thesis which has been documented and included. I further considered how to share my analytical framework in the form of a software programme, a prototype of which can be found in the appendix

    Traveling Dark Solitons in Superfluid Fermi Gases

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    Families of dark solitons exist in superfluid Fermi gases. The energy-velocity dispersion and number of depleted particles completely determines the dynamics of dark solitons on a slowly-varying background density. For the unitary Fermi gas we determine these relations from general scaling arguments and conservation of local particle number. We find solitons to oscillate sinusoidally at the trap frequency reduced by a factor of 1/31/\sqrt{3}. Numerical integration of the time-dependent Bogoliubov-de Gennes equation determines spatial profiles and soliton dispersion relations across the BEC-BCS crossover and proves consistent with the scaling relations at unitarity.Comment: Small changes in response to referee's comments; fig 1 revised and refs updated. Cross listed to nucl-th due to interest in the unitary Fermi ga

    Observation of Hybrid Soliton Vortex-Ring Structures in Bose-Einstein Condensates

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    We present the experimental discovery of compound structures comprising solitons and vortex rings in Bose-Einstein condensates (BECs). We examine both their creation via soliton-vortex collisions and their subsequent development, which is largely governed by the dynamics of interacting vortex rings. A theoretical model in three-dimensional (3D) cylindrical symmetry is also presented.Comment: 5 pages, 4 figures; submitted to PR

    Localization by entanglement

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    We study the localization of bosonic atoms in an optical lattice, which interact in a spatially confined region. The classical theory predicts that there is no localization below a threshold value for the strength of interaction that is inversely proportional to the number of participating atoms. In a full quantum treatment, however, we find that localized states exist for arbitrarily weak attractive or repulsive interactions for any number (>1>1) of atoms. We further show, using an explicit solution of the two-particle bound state and an appropriate measure of entanglement, that the entanglement tends to a finite value in the limit of weak interactions. Coupled with the non-existence of localization in an optimized quantum product state, we conclude that the localization exists by virtue of entanglement.Comment: 6 pages, 4 figures; final published version with small changes in response to reviewer comment
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