Dynamics stability and control of displaced non-Keplerian orbits

The dynamics, stability, and control of a large family of non-Keplerian orbits are investigated and mission applications are discussed. The orbits are generated by seeking equilibrium solutions to the two-body problem in a rotating frame of reference with an additional thrust-induced acceleration. Viewed from an inertial frame of reference, displaced circular orbits are obtained. Three main families of orbits are presented, and their local stability characteristics are investigated. Although it is found that there are unstable subfamilies of orbits, it is also shown that these orbits are controllable using linear state feedback. Impulse control is also investigated as a means of generating displaced orbits and is compared to continuous thrust control. It is demonstrated that these non-Keplerian orbits can be patched together to provide large additional families of orbits

Personal appraisal of the experience of a depressive disorder

Focuses on the rating of personal significance of the disorder in patients receiving ongoing treatment for Major Depression using the Personal Appraisal Inventory. Appraisal of the positive and negative options for managing the disorder; Prediction of the levels of depression, anxiety, disability and distress; Changes in the way people appraised the impact of disorder.Clara Bookless and Alexander McFarlane, John Claye

Psychiatric morbidity following a natural disaster: an Australian bushfire

This study investigated the prevalence of mental health problems after a major bushfire in Australia and examined the validity of the General Health Questionnaire (GHQ) (Goldberg 1978) against the Anxiety, Affective and Post-Traumatic Stress Disorder modules of the Diagnostic Interview Schedule (DIS; Robins et al. 1981). Study 1 was carried out 12 months after the Ash Wednesday bushfires and sought to include all the victims of the fires. Study 2 was conducted 20 months after the fires and included a sample of victims who had experienced major losses in the fires. Twelve months after the fires, 42% (n = 1,526) of the victims were defined as a potential psychiatric case using the GHQ. This rate indicated a significantly greater level of morbidity than found in communities that have not experienced a natural disaster. Twenty months after the fires, 23% (n = 43) were defined as "cases". The 28-item GHQ was found to be a valid instrument for defining the presence of psychiatric disorder in a disaster-effected community. The findings demonstrated that lasting psychiatric morbidity is associated with natural disasters

Individual differences in appraisal of depression

This work introduces the Personal Appraisal Inventory (PAI) that was designed to quantify the personal meaning of experiencing a psychiatric disorder. The need to develop this new instrument is discussed and the results of a study with patients diagnosed and receiving treatment for major depression is presented. Specifically, factor analysis of the PAI items and the variance in depression scores explained by these factors is outlined. The findings suggest that the PAI provides a significant inroad to identifying coherent patterns of personal meaning. © 1999 Elsevier Science Ltd.Bookless, Clara; Clayer, John; McFarlane, Alexander

Psychiatric disorder & disability in a rural community

This study examined the relationship between psychiatric disorder and disability in a rural community and the use of formal and informal services in the management of such disabilities. It was found that of the 26% of the surveyed population who obtained a positive current psychiatric diagnosis, 48.3% had required assistance in managing at least one activity of daily living. The majority of those seeking assistance in managing these functional problems did so from family and friends rather than from formal agencies. Psychiatric disorder was found to lead to disability as frequently as did physical disorder, with almost 50% of those who had experienced mental health problems reporting that they were currently unable to carry out at least one activity of daily living. The finding that assistance was sought primarily from family and friends raises important questions about the nature of psychiatric disorder as a public health problem