A Control-Theoretic Model of Hemodynamic Responses to Blood Volume Perturbation

This thesis presents a mathematical model to reproduce hemodynamic responses of different endpoints to the blood volume perturbation in circulation system. The proposed model includes three sub-models, which are a control-theoretic model relating blood volume response to blood volume perturbation, a physiologic-based model relating cardiac output response to blood volume perturbation, and a control-theoretic model relating mean arterial pressure response to cardiac output perturbation. Two unique characteristics of this hemodynamic model are that the model can reproduce responses accurately even with its simplicity, and can be easily understood by control engineers because of its physiological transparency. With these two advantages, closed-loop resuscitation controller evaluation can be performed in model-based approach instead of evaluating results from animal studies, which are relatively costly and time-consuming. In this thesis, the hemodynamic model was examined and evaluated by using experimental dataset collected from 11 animals. The results of system identification analysis, in-silico evaluation and parametric sensitivity analysis showed that the hemodynamic model may faithfully serve as a evaluation basis for the closed-loop resuscitation controllers

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 258)

This bibliography lists 308 reports, articles and other documents introduced into the NASA scientific and technical information system in April 1984

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 184

This bibliography lists 139 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1978

Dopaminergic basis for signalling belief updates, but not surprise, and the link to paranoia

Distinguishing between meaningful and meaningless sensory information is fundamental to forming accurate representations of the world. Dopamine is thought to play a central role in processing the meaningful information content of observations, which motivates an agent to update their beliefs about the environment. However, direct evidence for dopamine’s role in human belief updating is lacking. We addressed this question in healthy volunteers who performed a model-based functional magnetic resonance imaging (fMRI) task designed to separate the neural processing of meaningful and meaningless sensory information. We modelled participant behaviour using a normative Bayesian observer model, and used the magnitude of the model-derived belief update following an observation to quantify its meaningful information content. We also acquired positron emission tomography (PET) imaging measures of dopamine function in the same subjects. We show that the magnitude of belief updates about task structure (meaningful information), but not pure sensory surprise (meaningless information), are encoded in midbrain and ventral striatum activity. Using PET we show that the neural encoding of meaningful information is negatively related to dopamine-2/3 receptor availability in the midbrain and dexamphetamine-induced dopamine release capacity in the striatum. Trial-by-trial analysis of task performance indicated that subclinical paranoid ideation is negatively related to behavioural sensitivity to observations carrying meaningful information about the task structure. The findings provide direct evidence implicating dopamine in model-based belief updating in humans, and have implications for understating the pathophysiology of psychotic disorders where dopamine function is disrupted

Stochastic Pharmacokinetic-Pharmacodynamic Modeling for Assessing the Systemic Health Risk of Perfluorooctanoate (PFOA)

A phase 1 dose-escalation trial assessed the chemotherapeutic potential of ammonium perfluorooctanoate (APFO). Forty-nine primarily solid-tumor cancer patients who failed standard therapy received weekly APFO doses (50mg-1200mg) for six-weeks. Clinical chemistries and plasma PFOA (anionic APFO) were measured pre-dose and weekly thereafter. Several clinical measures including total cholesterol, high-density lipoproteins (HDL), thyroid stimulating hormone (TSH), and free thyroxine (fT4), relative to PFOA concentrations, were examined by: standard statistical analyses using general estimating equations (GEE) and a probabilistic analysis using probability distribution functions (pdf) at various PFOA concentrations; and a two-compartment pharmacokinetic/pharmacodynamic (PK/PD) model to directly estimate mean changes. Based on the GEE, the average rates of change in total cholesterol and fT4 associated with increasing PFOA were approximately -1.2x10−3mmol/L/μM and 2.8x10−3pmol/L/μM, respectively. The PK/PD model predicted more closely the trends observed in the data as well as the pdfs of biomarkers. A decline in total cholesterol was observed, with a clear transition in shape and range of the pdfs, manifested by the maximum value of the Kullback-Leibler (KL) divergence, that occurred at plasma PFOA between 420 and 565 μM (175,000–230,000 ng/mL). HDL was unchanged. An increase in fT4 was observed at a higher PFOA transition point, albeit TSH was unchanged. Our findings are consistent with some animal models and may motivate re-examination of the epidemiological studies to PFOA at levels several orders of magnitude lower than this study. These observational studies have reported contrary associations, but currently understood biology does not support the existence of such conflicting effects

Aerospace Medicine and Biology: A continuing bibliography, supplement 191

A bibliographical list of 182 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1979 is presented

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 292)

This bibliography lists 192 reports, articles and other documents introduced into the NASA scientific and technical information system in December, 1986

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 178

This bibliography lists 230 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1978

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 375)

This bibliography lists 212 reports, articles, and other documents recently introduced into the NASA Scientific and Technical Information System database. Subject coverage includes the following: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

Research reports: 1991 NASA/ASEE Summer Faculty Fellowship Program

The basic objectives of the programs, which are in the 28th year of operation nationally, are: (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participants' institutions; and (4) to contribute to the research objectives of the NASA Centers. The faculty fellows spent 10 weeks at MSFC engaged in a research project compatible with their interests and background and worked in collaboration with a NASA/MSFC colleague. This is a compilation of their research reports for summer 1991