A survey of comet missions

Survey of scientific mission possibilities to comets passing through solar syste

Relative motion of orbiting particles under the influence of perturbing forces. Volume 1: Summary

The relative motion for orbiting vehicles, under the influence of various perturbing forces, has been studied to determine what influence these inputs, and others, can have. The analytical tasks are discribed in general terms; the force types considered, are outlined modelled and simulated, and the capabilities of the computer programs which have evolved in support of this work are denoted

Relative motion of orbiting particles under the influence of perturbing forces. Volume 2: Analytical results

The mathematical developments carried out for this investigation are reported. In addition to describing and discussing the solutions which were acquired, there are compendia of data presented herein which summarize the equations and describe them as representative trace geometries. In this analysis the relative motion problems have been referred to two particular frames of reference; one which is inertially aligned, and one which is (local) horizon oriented. In addition to obtaining the classical initial values solutions, there are results which describe cases having applied specific forces serving as forcing functions. Also, in order to provide a complete state representation the speed components, as well as the displacements, have been described. These coordinates are traced on representative planes analogous to the displacement geometries. By this procedure a complete description of a relative motion is developed; and, as a consequence range rate as well as range information is obtained

Relative motion of orbiting particles under the influence of perturbing forces. Volume 3: Construction of relative motion traces

Geometric traces can be simply constructed to illustrate the relative motions experienced by particles in a number of problem situations. These diagrams describe the displacements and hodographs which arise as a consequence of initial value inputs and selected disturbance (force) conditions. Due to the linearization which is imposed on the mathematical formulation there is a separation of the in-plane and out-of-plane coordinate solutions. The construction of in-plane traces is easier to represent and to visualize. The out-of-plane geometries are the more complicated cases and generally need some added specializations in order to acquire figures which have some degree of symmetry and simplicity

Relative motion of orbiting satellites

The relative motion problem is analyzed, as a linearized case, and as a numerically determined solution to provide a time history of the geometries representing the motion state. The displacement history and the hodographs for families of solutions are provided, analytically and graphically, to serve as an aid to understanding this problem area. Linearized solutions to relative motion problems of orbiting particles are presented for the impulsive and fixed thrust cases. Second order solutions are described to enhance the accuracy of prediction. A method was developed to obtain accurate, numerical solutions to the intercept and rendezvous problem; and, special situations are examined. A particular problem related to relative motions, where the motion traces develop a cusp, is examined in detail. This phenomenon is found to be dependent on a particular relationship between orbital eccentricity and the inclination between orbital planes. These conditions are determined, and, example situations are presented and discussed

Tethered body problems and relative motion orbit determination

Selected problems dealing with orbiting tethered body systems have been studied. In addition, a relative motion orbit determination program was developed. Results from these tasks are described and discussed. The expected tethered body motions were examined, analytically, to ascertain what influence would be played by the physical parameters of the tether, the gravity gradient and orbit eccentricity. After separating the motion modes these influences were determined; and, subsequently, the effects of oscillations and/or rotations, on tether force, were described. A study was undertaken, by examining tether motions, to see what type of control actions would be needed to accurately place a mass particle at a prescribed position relative to a main vehicle. Other applications for tethers were studied. Principally these were concerned with the producing of low-level gee forces by means of stabilized tether configurations; and, the initiation of free transfer trajectories from tether supported vehicle relative positions

What are the resourcing requirements for an Aboriginal and Torres Strait Islander primary healthcare research project?

Objective and importance To explore the role of resourcing during an Aboriginal and Torres Strait Islander primary healthcare research project. Study type Process evaluation using grounded theory approaches of a national Aboriginal and Torres Strait Islander research project (N=500) named Getting it Right: The validation study. Methods Qualitative semi-structured interviews with thirty-six primary healthcare staff and four community members from nine of ten primary healthcare services (participating services) involved in the research project. Interviews included questions about the resources needed to conduct the research project, including flexible reimbursement to participating services (allocated within services), human resources and reimbursement to research participants (vouchers). Qualitative data were triangulated with participant feedback (questions about the aPHQ-9 [depression screening tool under examination] and free-text feedback collected during the research project), study administrative data (budgets, contracts, communication logs and ethics correspondence) and field notes kept by the interviewer. Results Three themes were identified: 1) the influence of reimbursement on participating services and the research project: 2) the influence of human resources on the research project at participating services; and 3) the consequences of offering vouchers to reimburse research participants. Reimbursement was allocated to research expenses (human resources and logistics) or non-research expenses (service operations, equipment and conference attendance costs). Most services opted to offer vouchers to compensate participants for their time, which staff considered was appropriate recognition of participants’ contributions and facilitated recruitment. Some staff described some potential unintended negative consequences from vouchers, including creating a welfare mentality or the wrong precedent. Conclusion Primary healthcare research should have sufficient resourcing available, including human resource capacity, to achieve research targets. Research planning should include consideration of the existing commitments, priorities and human capacity needs of services and patients

Healthcare expenditure on Indigenous and non-Indigenous Australians at high risk of cardiovascular disease

Background: In spite of bearing a heavier burden of death, disease and disability, there is mixed evidence as to whether Indigenous Australians utilise more or less healthcare services than other Australians given their elevated risk level. This study analyses the Medicare expenditure and its predictors in a cohort of Indigenous and non-Indigenous Australians at high risk of cardiovascular disease. Methods: The healthcare expenditure of participants of the Kanyini Guidelines Adherence with the Polypill (GAP) pragmatic randomised controlled trial was modelled using linear regression methods. 535 adult (48% Indigenous) participants at high risk of cardiovascular disease (CVD) were recruited through 33 primary healthcare services (including 12 Aboriginal Medical Services) across Australia. Results: There was no significant difference in the expenditure of Indigenous and non-Indigenous participants in non-remote areas following adjustment for individual characteristics. Indigenous individuals living in remote areas had lower MBS expenditure ($932 per year P< 0.001) than other individuals. MBS expenditure was found to increase with being aged over 65 years ($128, p=0.013), being female ($472, p=0.003), lower baseline reported quality of life ($102 per 0.1 decrement of utility p=0.004) and a history of diabetes ($324, p=0.001), gout ($631, p=0.022), chronic obstructive pulmonary disease ($469, p=0.019) and established CVD whether receiving guideline-recommended treatment prior to the trial ($452, p=0.005) or not ($483, p=0.04). When controlling for all other characteristics, morbidly obese patients had lower MBS expenditure than other individuals (-$887, p=0.002). Conclusion: The findings suggest that for the majority of participants, once individuals are engaged with a primary care provider, factors other than whether they are Indigenous determine the level of Medicare expenditure for each person. Trial Registration: Australian New Zealand Clinical Trials Registry ACTRN 126080005833347

Nonequilibrium thermodynamics and energy efficiency in weight loss diets

Carbohydrate restriction as a strategy for control of obesity is based on two effects: a behavioral effect, spontaneous reduction in caloric intake and a metabolic effect, an apparent reduction in energy efficiency, greater weight loss per calorie consumed. Variable energy efficiency is established in many contexts (hormonal imbalance, weight regain and knock-out experiments in animal models), but in the area of the effect of macronutrient composition on weight loss, controversy remains. Resistance to the idea comes from a perception that variable weight loss on isocaloric diets would somehow violate the laws of thermodynamics, that is, only caloric intake is important ("a calorie is a calorie"). Previous explanations of how the phenomenon occurs, based on equilibrium thermodynamics, emphasized the inefficiencies introduced by substrate cycling and requirements for increased gluconeogenesis. Living systems, however, are maintained far from equilibrium, and metabolism is controlled by the regulation of the rates of enzymatic reactions. The principles of nonequilibrium thermodynamics which emphasize kinetic fluxes as well as thermodynamic forces should therefore also be considered