Polarizable colloids are expected to form crystalline equilibrium phases when exposed to a steady, uniform field. However, when colloids become localized this field-induced phase transition arrests ...and the suspension persists indefinitely as a kinetically trapped, percolated structure. We anneal such gels formed from magneto-rheological fluids by toggling the field strength at varied frequencies. This processing allows the arrested structure to relax periodically to equilibrium—colloid-rich, cylindrical columns. Two distinct growth regimes are observed: one in which particle domains ripen through diffusive relaxation of the gel, and the other where the system-spanning structure collapses and columnar domains coalesce apparently through field-driven interactions. There is a stark boundary as a function of magnetic field strength and toggle frequency distinguishing the two regimes. These results demonstrate how kinetic barriers to a colloidal phase transition are subverted through measured, periodic variation of driving forces. Such directed assembly may be harnessed to create unique materials from dispersions of colloids.
For many years, there have been anecdotal reports of vision changes by astronauts following short and long-duration spaceflight. Much of this was attributed to hyperopic shifts related to the age of ...the flying population. However, it has recently been recognized that vision changes are actually quite common in astronauts and are associated with a constellation of findings including elevated intracranial pressure, optic disc edema, globe flattening, optic nerve sheath thickening, hyperopic shifts and retinal changes. With advanced imaging modalities available on the ground along with the fidelity of in-flight diagnostic capabilities previously unavailable, information on this newly recognized syndrome is accumulating. As of this writing, 11 cases of visual impairment experienced by astronauts during missions on-board the International Space Station (ISS) have been documented and studied. Although the exact mechanisms of the vision changes are unknown, it is hypothesized that increased intracranial pressure (ICP) is a contributing factor.
Microgravity is the dominant cause of many physiological changes during spaceflight and is thought to contribute significantly to the observed ophthalmic changes. However, several secondary factors that could contribute to increased ICP and vision changes in spaceflight have been proposed. Possible contributors include microgravity-induced cephalad fluid shift, venous obstruction due to microgravity-induced anatomical shifts, high levels of spacecraft cabin carbon dioxide, heavy resistive exercise, and high sodium diet. Individual susceptibility to visual impairment is not fully understood, though a demographic of affected astronauts is emerging.
This paper describes the current understanding of this newly recognized syndrome, presents data from 11 individual cases, and discusses details of potential contributing factors. The occurrence of visual changes in long duration missions in microgravity is one of the most significant clinical issues to date for the human spaceflight community, and a comprehensive understanding of the issue at whole is critical to ensure safe space exploration in the future.
► A syndrome of vision and neuroanatomical changes associated with spaceflight is described. ► Data from 11 individual cases in long duration astronauts are presented. ► Anatomy and physiology of the findings are discussed and reviewed. ► The current understanding of the ‘microgravity ocular syndrome’ is offered.
BACKGROUND: While catastrophic spaceflight events resulting in crew loss have occurred, human spaceflight has never suffered an on-orbit fatality with survival of other crewmembers on board. ...Historical plans for management of an on-orbit fatality have included some consideration
for forensic documentation and sample collection, human remains containment, and disposition of remains; however, such plans have not included granular detailing of crew or ground controller actions. The NASA Johnson Space Center Contingency Medical Operations Group, under authority from the
Space and Occupational Medicine Branch, the Space Medicine Operations Division, and the Human Health and Performance Directorate, undertook the development of a comprehensive plan, including an integrated Mission Control Center response for flight control teams and Flight Surgeons for a single
on-orbit crew fatality on the International Space Station (ISS) and subsequent events. Here we detail the operational considerations for a crew fatality should it occur during spaceflight onboard the ISS, including forensic and timeline constraints, behavioral health factors, and considerations
for final disposition of decedent remains. Future considerations for differential survival and crewmember fatality outside of low-Earth orbit operations will additionally be discussed, including consideration of factors unique to planetary and surface operations and disposition limitations
in exploration spaceflight. While the efforts detailed herein were developed within the constraints of the ISS concept of operations, future platforms may benefit from the procedural validation and product verifications steps described. Ultimately, any response to spaceflight fatality must
preserve the goal of handling decedent remains and disposition with dignity, honor, and respect.Stepaniak PC, Blue RS, Gilmore S, Beven GE, Chough NG, Tsung A, McMonigal KA, Mazuchowski EL II, Bytheway JA, Lindgren KN, Barratt MR. Operational considerations for crew fatality on the
International Space Station. Aerosp Med Hum Perform. 2023; 94(9):705–714.
BACKGROUND: Maintenance and disposition of decedent remains during spaceflight require the isolation of biohazardous products of decomposition in microgravity and in the absence of refrigeration. ...Containment and isolation options would preferably offer sufficient time to enable
crew and ground support teams to determine appropriate disposition of remains and even potentially return remains to the Earth. The pilot study described herein undertook an effort to develop a postmortem containment unit for the isolation and maintenance of decedent remains in a microgravity
environment.METHODS: Commercial off-the-shelf containment units were modified to meet the needs of a microgravity spaceflight environment and to offer the best likelihood of successful containment and management of remains. A subsequent evaluation of modified containment unit performance
was undertaken utilizing human cadavers, with measurement and analysis of volatile off-gassing over time followed by impact testing of the units containing cadaverous remains in a simulated spaceflight vehicle seat.RESULTS: Modifications were implemented without significant negative
design impact. Failure was observed in one modified unit after 9 d and attributed to improper filter application. The remaining unit successfully contained remains beyond the intended endpoint of the study.DISCUSSION: These pilot efforts offer important insight into the development
of effective postmortem containment options for future spaceflight. Further study is needed to ensure repeatability of the findings and to further characterize the failure modes of the modified units evaluated, the impact of microgravity conditions, and the identification of additional modifications
that would improve remains disposition.Houser T, Lindgren KN, Mazuchowski EL II, Barratt MR, Haines DC, Jayakody M, Blue RS, Bytheway JA, Stepaniak PC. Remains containment considerations for death in low-Earth orbit. Aerosp Med Hum Perform. 2023; 94(5):368-376.
BACKGROUND:A number of ophthalmic findings including optic disc edema, globe flattening, and choroidal folds have been observed in several astronauts after long-duration space flights. The authors ...report the first astronaut with previously documented postflight ophthalmic abnormalities who developed new pathological changes after a repeat long-duration mission.
METHODS:A case study of an astronaut with 2 long-duration (6 months) exposures to microgravity. Before and after his first long-duration space flight, he underwent complete eye examination, including fundus photography. Before and after his second flight, 9 years later, he underwent fundus photography, optical coherence tomography, ocular ultrasonography, and brain magnetic resonance imaging, as well as in-flight fundus photography and ultrasound.
RESULTS:After his first long-duration mission, the astronaut was documented to have eye findings limited to unilateral choroidal folds and a single cotton wool spot. During a subsequent 6-month mission, he developed more widespread choroidal folds and new onset of optic disc edema in the same eye.
CONCLUSION:Microgravity-induced anatomical changes that occurred during the first mission may have set the stage for recurrent or additional changes when the astronaut was subjected to physiological stress of repeat space flight.
Posterior globe flattening has been well-documented in astronauts both during and after long-duration space flight (LDSF) and has been observed as early as 10 days into a mission on the International ...Space Station. Globe flattening (GF) is thought to be caused by the disc centred anterior forces created by elevated volume and/or pressure within the optic nerve sheath (ONS). This might be the result of increased intracranial pressure, increased intraorbital ONS pressure from compartmentalisation or a combination of these mechanisms. We report posterior GF in three astronauts that has persisted for 7 years or more following their return from LDSFs suggesting that permanent scleral remodelling may have occurred.
Advances over the past decades in space flight technology have allowed U.S., Russian, and other space programs to not only increase the frequency of manned space flights but also to increase the ...duration of these flights. As such, a large body of knowledge has been developed regarding the ways in which space flight affects the health of the personnel involved. Now, for the first time, this body of clinical knowledge on how to diagnose and treat conditions that either develop during a mission or because of a mission has been compiled by Drs. Michael R. Barratt and Sam L. Pool of the NASA/Johnson Space Center.
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