ABSTRACT
In the last decade, NASA and other space exploration organizations have focused on making crewed missions to different locations in our solar system a priority. To ensure the crew members' safety in a harsh radiation environment outside the protection of the geomagnetic field and atmosphere, a robust radiation protection system needs to be in place. Passive shielding methods, which use mass shielding, are insufficient as a standalone means of radiation protection for long-term deep-space missions. Active shielding methods, which use electromagnetic fields to deflect charged particles, have the potential to be a solution that can be used along with passive shielding to make deep-space travel safer and more feasible. Past active shielding studies have demonstrated that substantial technological advances are required for active shielding to be a reality. However, active shielding has shown potential for near-future implementation when used to protect against solar energetic particles, which are less penetrating than galactic cosmic rays (GCRs). This study uses a novel approach to investigate the impacts of passive and active shielding for protection against extreme solar particle events (SPEs) and free-space GCR spectra under solar minimum and solar maximum conditions. Hybrid shielding configuration performance is assessed in terms of effective dose and radiobiological effectiveness (RBE)-weighted dose reduction. A novel electrostatic shielding configuration consisting of multiple charged planes and charged rods was chosen as the base active shielding configuration. After a rigorous optimization process, two hybrid shielding configurations were chosen based on their ability to reduce RBE-weighted dose and effective dose. For protection against the extreme SPE, a hybrid active-passive shielding configuration was chosen, where active shielding was placed outside of passive shielding. In the case of GCRs, to gain additional reduction compared to passive shielding, the passive shielding configuration was placed before the active shielding to intentionally fragment HZE ions to improve shielding performance.
Subject(s)
Cosmic Radiation , Radiation Protection , Atmosphere , Electromagnetic Fields , Protective Devices , HumansABSTRACT
BACKGROUND AND IMPORTANCE: Since Trousseau's initial publication, the development of thromboembolic events related to malignancy has been well established. The pathophysiology of this is understood to be through activation of the coagulation cascade through neoplastic cells themselves or the therapy initiated (chemotherapy or surgery). To date, there have been a variety of studies, such as the OASIS-CANCER trial, which highlight the relationship of hypercoagulability to ischemic stroke. Despite these efforts, clear evidence is lacking for the utilization of antiplatelet or anticoagulation therapy in the secondary prevention of stroke following mechanical thrombectomy in patients with suspected or confirmed malignancy. CLINICAL PRESENTATION: A 71-year-old female with a history of immune thrombocytopenia, diabetes mellitus, and hypertension who was undergoing an evaluation for a lung nodule, later determined to be adenocarcinoma of the lung, underwent three successful mechanical thrombectomies for acute ischemic stroke with large vessel occlusion over a one month period. This patient had improved National Institutes of Health Stroke Scale (NIHSS) scores following each of her thrombectomies. However, her history of immune thrombocytopenia and underlying malignancy complicated her discharge medication regimen following each of her thrombectomies and may have contributed to her repeat strokes. CONCLUSION: Clear guidance is lacking regarding the utilization of antiplatelet and anticoagulation therapy in patients with suspected or confirmed malignancy following mechanical thrombectomy. Review of the literature suggests that controlling a patient's hypercoagulability may lead to improved clinical outcomes, but further clinical trials are warranted.
