Incorporation of Mission Design Constraints in Floquet Mode and Hamiltonian Structure-Preserving Orbital Maintenance Control Strategies for Libration Point Orbits

Libration point orbits are, in general, inherently unstable. Without the presence of corrective maneuvers a spacecraft will diverge from the vicinity of such trajectories. In this research effort, two orbital maintenance control strategies are studied: the impulsive Floquet Mode (FM) controller and the continuous Hamiltonian Structure-Preserving (HSP) controller. These two controllers are further developed to incorporate real-world mission design constraints. The FM controller is modified to accommodate feasible maneuver directions that are constrained to a plane or a line. This controller is shown to be applicable for orbital station-keeping of spin stabilized spacecraft that are only equipped with either tangential thrusters or axial thrusters. The HSP controller is extended for application to general three-dimensional hyperbolic libration point orbits, and then discretized to account for the minimum time required for orbit determination and/or scientific operations. Both controllers are applied to an unstable 1 halo orbit in the Sun-Earth/Moon system. The performances of these controllers are examined under the impacts of the spacecraft’s operation errors and mission design constraints. Simulation results suggest that the FM controller is capable of maintaining the motion of the spacecraft in the vicinity of the desired reference trajectory for the duration of the simulation, while satisfying all mission design constraints. The discrete-time MHSP controller proves to be able to improve the stability of the nominal trajectory by reducing the value of the unstable Poincare exponent of the reference orbit

Crucifixion and median neuropathy.

Crucifixion as a means of torture and execution was first developed in the 6th century B.C. and remained popular for over 1000 years. Details of the practice, which claimed hundreds of thousands of lives, have intrigued scholars as historical records and archaeological findings from the era are limited. As a result, various aspects of crucifixion, including the type of crosses used, methods of securing victims to crosses, the length of time victims survived on the cross, and the exact mechanisms of death, remain topics of debate. One aspect of crucifixion not previously explored in detail is the characteristic hand posture often depicted in artistic renditions of crucifixion. In this posture, the hand is clenched in a peculiar and characteristic fashion: there is complete failure of flexion of the thumb and index finger with partial failure of flexion of the middle finger. Such a "crucified clench" is depicted across different cultures and from different eras. A review of crucifixion history and techniques, median nerve anatomy and function, and the historical artistic depiction of crucifixion was performed to support the hypothesis that the "crucified clench" results from proximal median neuropathy due to positioning on the cross, rather than from direct trauma of impalement of the hand or wrist

Quantitative Mapping of Lung Ventilation Using Hyperpolarized Gas Magnetic Resonance Imaging

The main objective of this project was to develop and implement techniques for high-resolution quantitative imaging of ventilation in lungs using hyperpolarized gas magnetic resonance imaging (MRI). Pulmonary ventilation is an important aspect of lung function and is frequently compromised through several different mechanisms and at varying degrees in presence of certain lung conditions, such as chronic obstructive pulmonary diseases. The primary focus of this development is on large mammalian species as a steppingstone towards translation to human subjects. The key deliverables of this project are a device for real-time mixing and delivery of hyperpolarized gases such as 3He and 129Xe in combination with O2, an MRI acquisition scheme for practical imaging of ventilation signal build-up in the lungs, and a robust mathematical model for estimation of regional fractional ventilation values at a high resolution. A theoretical framework for fractional gas replacement in the lungs is presented to describe MRI signal dynamics during continuous breathing of a mixture of hyperpolarized gases in presence of several depolarization mechanisms. A hybrid ventilation and imaging acquisition scheme is proposed to acquire a series of images during short end-inspiratory breath-holds over several breaths. The sensitivity of the estimation algorithm is assessed with respect to noise, model uncertainty and acquisition parameters, and subsequently an optimal set of acquisition parameters is proposed to minimize the fractional ventilation estimation error. This framework is then augmented by an undersampled parallel MRI scheme to accelerate image acquisition to enable fractional ventilation imaging over the entire lung volume in a single pass. The image undersampling was also leveraged to minimize the coupling associated with signal buildup in the airways and the irreversible effect of RF pulses. The proposed technique was successfully implemented in pigs under mechanical ventilation, and preliminary measurements were performed in an adult human subject under voluntary breathing

Performance Analysis of Coulomb Counting Approach for State of Charge Estimation in Li-Ion Batteries

Accurate state of charge (SOC) estimation in rechargeable batteries is always a challenge since many parameters can affect the SOC of the battery. Amongst all the developed methods for SOC estimation, Coulomb counting has been one of the most common and traditional methods. Nevertheless, the accuracy of this method is debatable. It was assumed that Coulomb counting can accurately estimate SOC by assuming the battery capacity and initial SOC. In this thesis, we analyze the Coulomb counting method thoroughly and we showed that this method is susceptible uncertainties. The sources of uncertainties that affect Coulomb counting accuracy are: (i) current measurement error; (ii) current integration approximation error; (iii) battery capacity uncertainty; and the (iv) timing oscillator error/drift. The SOC error due to all these uncertainties can be categorized into two forms; time-cumulative and SOC-proportional. The time-cumulative error increases over time and can invalidate SOC estimation by Coulomb counting. The SOC-proportional error increase with the accumulated SOC and it can affect SOC accuracy within one cycle of charge/discharge. A simulation analysis is presented to demonstrate and verify the effect of these uncertainties under several realistic scenarios. We also have discussed the approaches to reduce these uncertainties

Quantitative Assessment Of Brain Iron Content As A Function Of Age Using Magnetic Resonance Imaging

As the most abundant transition metal in the brain, iron is known to play a key role in a variety of functional and cellular processes. Recent in vivo and post-mortem studies have shown that the levels of iron deposition in the brain, particularly in deep gray matter nuclei, vary as a function of age. On the other hand, elevated iron has also been associated with some neurodegenerative diseases such as Multiple Sclerosis (MS) and Parkinson’s disease (PD) among others. Magnetic Resonance Imaging (MRI) is a widely used non-invasive and non-ionizing imaging modality which is sensitive to magnetic properties of materials through their magnetic susceptibilities. This makes it particularly useful in imaging as iron (which is paramagnetic) and calcium (which is diamagnetic). Recent developments in magnetic susceptibility mapping have made it possible to track iron changes in the brain. In this thesis, Quantitative Susceptibility Mapping (QSM) is used to establish a baseline of iron content in the basal ganglia, midbrain, and cerebellar major nuclei as a function of age in healthy controls using both global (whole 3D structural region) and regional (high iron content region) analyses. In agreement with previous studies, we found that in the global analysis a positive linear susceptibility-age correlation was observed in the putamen, caudate nucleus, and red nucleus while the susceptibility distributions across the lifespan were quite scattered in the globus pallidus, substantia nigra, thalamus, pulvinar thalamus and dentate nucleus. All structures, with the exception of the thalamus, showed increasing susceptibility trend as a function of age in the whole-region analysis. However, in the high iron content region, strong and considerably less scattered correlations were shown between age and magnetic susceptibility in most of the structures, except for the thalamus. These sensitive and robust regional susceptibility-age correlations have the potential to be utilized as a new baseline to investigate abnormal iron content in neurological diseases

Intraoperative Extracorporeal Irradiation for the Treatment of the Meningioma-Infiltrated Calvarium.

Objectives Complete removal of infiltrated bone is required to achieve a Simpson Grade 1 meningioma resection. Reconstruction of the resulting bone defect is typically achieved with a nonnative implant that can result in poor cosmesis, foreign body reaction, or infection. Extracorporeal irradiation and reimplantation of tumorous bone has been used for limb-sparing surgery with excellent results, but this treatment option is not routinely considered in meningioma surgery. We present a case of anterior fossa meningioma with tumorous overlying calvarium that was successfully managed with intraoperative extracorporeal irradiation and reimplantation. Design, Setting, and Participant A 37-year-old woman with persistent chronic headaches was found to have an anterior skull base meningioma with extension into the forehead frontal bone. Concurrently with mass resection, the bone flap was irradiated intraoperatively with 120 Gy. After resection of the tumor, the bone flap was replaced in its native position. Main Outcome Measures and Results Twenty-nine months postoperatively, the patient had an excellent cosmetic outcome with no radiographic evidence of tumor recurrence or significant bone flap resorption. Conclusion Intraoperative extracorporeal irradiation of tumorous calvaria during meningioma surgery is an effective, logistically feasible treatment option to achieve local tumor control and excellent cosmetic outcome