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All sources NASA NTRS DOE OSTI

NASA NTRS1990

Design and fabrication of a long-life Stirling cycle cooler for space application. Phase 3: Prototype model

A second-generation, Stirling-cycle cryocooler (cryogenic refrigerator) for space applications, with a cooling capacity of 5 watts at 65 K, was recently completed. The refrigerator, called the Prototype Model, was designed with a goal of 5 year life with no degradation in cooling performance. The free displacer and free piston of the refrigerator are driven directly by moving-magnet linear motors with the moving elements supported by active magnetic bearings. The use of clearance seals and the absence of outgassing material in the working volume of the refrigerator enable long-life operation with no deterioration in performance. Fiber-optic sensors detect the radial position of the shafts and provide a control signal for the magnetic bearings. The frequency, phase, stroke, and offset of the compressor and expander are controlled by signals from precision linear position sensors (LVDTs). The vibration generated by the compressor and expander is cancelled by an active counter balance which also uses a moving-magnet linear motor and magnetic bearings. The driving signal for the counter balance is derived from the compressor and expander position sensors which have wide bandwidth for suppression of harmonic vibrations. The efficiency of the three active members, which operate in a resonant mode, is enhanced by a magnetic spring in the expander and by gas springs in the compressor and counterbalance. The cooling was achieved with a total motor input power of 139 watts. The magnetic-bearing stiffness was significantly increased from the first-generation cooler to accommodate shuttle launch vibrations.

Keung, C.↗

NASA NTRS1991

Experimental modelling of lightning interaction phenomena with a free potential conducting objects

Laboratory experiments were conducted to investigate the physical processes of the development of air discharge and its interaction with free potential conducting objects. The space-time development of lightning in gaps was recorded by a motion picture camera and an optoelectronic transducer. The electric field at different points in the gap was measured using a Pockels device both in the leader stage and in the stage of the return stroke. Experimental results of the streamer zone length measurements in the gaps with lengths up to 65 meters are presented. The physical processes occurring during the interaction of positive and negative long sparks with isolated objects were investigated. The striking probability of isolated conducting spheres with different diameters and the dependence of the strike on the location of the gap are investigated.

Chernov, E. N.↗

DOE OSTI2011

Design for Manufacturing for Energy Absorption Systems

In the typical scenario of a helicopter crash, impact with the ground is preceded by a substantially vertical drop, with the result that a seated occupant of a helicopter experiences high spinal loads and pelvic deceleration during such crash due to the sudden arresting of vertical downward motion. It has long been recognized that spinal injuries to occupants of helicopters in such crash scenario can be minimized by seat arrangements which limit the deceleration to which the seated occupant is subjected, relative to the helicopter, to a predetermined maximum, by allowing downward movement of the seated occupant relative to the helicopter, at the time of impact with the ground, under a restraining force which, over a limited range of such movement, is limited to a predetermined maximum. In practice, significant benefits, in the way of reduced injuries and reduced seriousness of injuries, can be afforded in this way in such crash situations even where the extent of such controlled vertical movement permitted by the crashworthy seat arrangement is quite limited. Important increase of accident safety is reached with the installation of crashworthy shock absorbers on the main landing gear, but this solution is mostly feasible on military helicopters with long fixed landing gear. Seats can then give high contribution to survivability. Commonly, an energy absorber is a constant load device, if one excludes an initial elastic part of the load-stroke curve. On helicopter seats, this behavior is obtained by plastic deformation of a metal component or scraping of material. In the present work the authors have studied three absorption systems, which differ in relation to their shape, their working conditions and their constructive materials. All the combinations have been analyzed for applications in VIP helicopter seats.

42 ENGINEERING↗

NASA NTRS1977

Simulation of radiation from lightning return strokes: The effects of tortuosity

A Monte Carlo simulation has been developed for the electromagnetic fields radiated from a tortuous lightning channel. This was done using a piecewise linear model for the channel and employing for each element the field radiated by a traveling wave on an arbitrarily oriented filament over a conducting plane. The simulation reproduces experimental data reasonably well and had been used to study the effects of tortuousity on the fields radiated by return strokes. Tortuosity can significantly modify the radiated waveform, tending to render it less representative of the current pulse and more nearly unipolar than one would expect based on the theory for a long straight channel. In the frequency domain the effect of tortuosity is an increase in high frequency energy as compared with an equivalent straight channel. The extent of this increase depends on the mean length of the elements comprising the channel and can be significant.

Levine, D. M.↗

NASA NTRS1978

Simulation of radiation from lightning return strokes - The effects of tortuosity

A Monte Carlo simulation has been developed for the electromagnetic fields radiated from a tortuous lightning channel. This was done using a piecewise linear model for the channel and employing for each element the field radiated by a traveling wave on an arbitrarily oriented filament over a conducting plane. The simulation reproduces experimental data reasonably well and has been used to study the effects of tortuosity on the fields radiated by return strokes. Tortuosity can significantly modify the radiated waveform, tending to render it less representative of the current pulse and more nearly unipolar than one would expect based on the theory for a long straight channel. In the frequency domain the effect of tortuosity is an increase in high frequency energy as compared with an equivalent straight channel. The extent of this increase depends on the mean length of the elements comprising the channel and can be significant.

Levine, D. M.↗

DOE OSTI2019

Should All Low-risk Patients Now Be Considered for TAVR? Operative Risk, Clinical, and Anatomic Considerations

Purpose of Review: This article reviews the current data on TAVR in low-risk patients with severe, symptomatic aortic stenosis, highlights the results of the recently published Medtronic Low Risk Randomized Study and PARTNER 3 trials, and describes specific clinical, anatomic, and procedural considerations regarding the optimal treatment choice in this population. Recent Findings: In low-risk patients, the Medtronic Low Risk Randomized Study demonstrated TAVR to be non-inferior to surgery with respect to the composite endpoint of death or disabling stroke while PARTNER 3 trial proved TAVR to be superior to surgery with regard to the composite endpoint of death, stroke, or rehospitalization. Summary: Recent trials demonstrate the safety and efficacy of TAVR in low-risk patients and have led to an FDA indication for the use of TAVR in these patients. However, the lack of long-term data on the rate of transcatheter valve deterioration in the younger population, higher incidence of paravalvular leak and pacemaker implantation following TAVR, along with certain intrinsic anatomic factors remain potential challenges to generalize TAVR in all low surgical risk patients. We describe specific clinical, anatomic, and procedural considerations regarding the optimal treatment choice for low-risk patients with severe, symptomatic AS.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2013

Vinpocetine attenuates lipid accumulation and atherosclerosis formation

Highlights: •Vinpocetine attenuates hyperlipidemia-induced atherosclerosis in a mouse model. •Vinpocetine antagonizes ox-LDL uptake and accumulation in macrophages. •Vinpocetine blocks the induction of ox-LDL receptor LOX-1 in vitro and in vivo. -- Abstract: Atherosclerosis, the major cause of myocardial infarction and stroke, is a chronic arterial disease characterized by lipid deposition and inflammation in the vessel wall. Cholesterol, in low-density lipoprotein (LDL), plays a critical role in the pathogenesis of atherosclerosis. Vinpocetine, a derivative of the alkaloid vincamine, has long been used as a cerebral blood flow enhancer for treating cognitive impairment. Recent study indicated that vinpocetine is a potent anti-inflammatory agent. However, its role in the pathogenesis of atherosclerosis remains unexplored. In the present study, we show that vinpocetine significantly reduced atherosclerotic lesion formation in ApoE knockout mice fed with a high-fat diet. In cultured murine macrophage RAW264.7 cells, vinpocetine markedly attenuated oxidized LDL (ox-LDL) uptake and foam cell formation. Moreover, vinpocetine greatly blocked the induction of ox-LDL receptor 1 (LOX-1) in cultured macrophages as well as in the LOX-1 level in atherosclerotic lesions. Taken together, our data reveal a novel role of vinpocetine in reduction of pathogenesis of atherosclerosis, at least partially through suppressing LOX-1 signaling pathway. Given the excellent safety profile of vinpocetine, this study suggests vinpocetine may be a therapeutic candidate for treating atherosclerosis.

60 APPLIED LIFE SCIENCES↗

NASA NTRS1987

An electromechanical attenuator/actuator for Space Station docking

The development of a docking system for aerospace vehicles has identified the need for reusable and variably controlled attenuators/actuators for energy absorption and compliance. One approach to providing both the attenuator and the actuator functions is by way of an electromechanical attenuator/actuator (EMAA) as opposed to a hydraulic system. The use of the electromechanical devices is considered to be more suitable for a space environment because of the absence of contamination from hydraulic fluid leaks and because of the cost effectiveness of maintenance. A smart EMAA that uses range/rate/attitude sensor information to preadjust a docking interface to eliminate misalignments and to minimize contact and stroking forces is described. A prototype EMAA was fabricated and is being tested and evaluated. Results of preliminary testing and analysis already performed have established confidence that this concept is feasible and will provide the desired reliability and low maintenance for repetitive long term operation typical of Space Station requirements.

Stokes, Lebarian↗

NASA NTRS2015

Establishing a Disruptive New Capability for NASA to Fly UAV's into Hazardous Conditions

A 2015 NASA Aeronautics Mission "Seedling" Proposal is described for a Severe-Environment UAV (SE-UAV) that can perform in-situ measurements in hazardous atmospheric conditions like lightning, volcanic ash and radiation. Specifically, this paper describes the design of a proof-of-concept vehicle and measurement system that can survive lightning attachment during flight operations into thunderstorms. Elements from three NASA centers draw together for the SE-UAV concept. 1) The NASA KSC Genesis UAV was developed in collaboration with the DARPA Nimbus program to measure electric field and X-rays present within thunderstorms. 2) A novel NASA LaRC fiber-optic sensor uses Faraday-effect polarization rotation to measure total lightning electric current on an air vehicle fuselage. 3) NASA AFRC's state-of-the-art Fiber Optics and Systems Integration Laboratory is envisioned to transition the Faraday system to a compact, light-weight, all-fiber design. The SE-UAV will provide in-flight lightning electric-current return stroke and recoil leader data, and serve as a platform for development of emerging sensors and new missions into hazardous environments. NASA's Aeronautics and Science Missions are interested in a capability to perform in-situ volcanic plume measurements and long-endurance UAV operations in various weather conditions. (Figure 1 shows an artist concept of a SE-UAV flying near a volcano.) This paper concludes with an overview of the NASA Aeronautics Strategic Vision, Programs, and how a SE-UAV is envisioned to impact them. The SE-UAV concept leverages high-value legacy research products into a new capability for NASA to fly a pathfinder UAV into hazardous conditions, and is presented in the SPIE DSS venue to explore teaming, collaboration and advocacy opportunities outside NASA.

Ely, Jay↗

NASA NTRS1987

Peripheral sensory processing in mammalian gravity receptors - Observations of ciliary tuft configurations

Scanning electron microscopy was used to study dynamic polarizations of clustered cells of the anterior part of rat saccular macula and to shed light on the possible roles of two types of hair cells integrated into the same neural circuitry: those with short stereocilia and long kinocilium (ss/lk), and those with long stereocilia and still longer kinocilium (ls/lk). It was found that the ss/lk-type cells could be further subdivided into two types, whereas the ls/lk cells consisted of four major kinds. It was also found that the kinocilium was most often fixed in a recovery stroke position (curved basally, and the upper portion projected back over the tuft) and that the kinocilia were not aligned in parallel in any given part of a macula, even though each cilium pointed in the proper direction relative to the striola line. The possibility of a relationship between the ciliary tuft morphology and the function of the hair cell of which it is a part is discussed.

Ross, Muriel D.↗

NASA NTRS1983

Advanced Automotive Diesel Assessment Program, executive summary

The objectives of this analytical study were: to select one advanced automotive diesel engine (AAD) concept which would increase the tank mileage of a 3,000 pound passenger car from the present 35 mpg to at least 52 mpg; to identify long term component research and development work required to bring the selected concept to fruition; and to prepare a development strategy that will bring the selected concept to a prototype testing phase. Cummins Engine Company has completed this study. The selected concept is a 4 stroke cycle, direct injection, spark assisted, advanced adiabatic diesel engine with positive displacement compounding plus expander and part load air preheating. The engine does not use a liquid coolant nor liquid lubricants. It is a 4 cylinder, in-line, 77 mm bore x 77 mm stroke, 1.434 liters displacement engine weighing 300 lb, and rated at 70 BHP at 3000 rpm. Installation dimensions are 621 mm length x 589 mm width x 479 mm height (24.4 inch x 22 inch x 18.9 inch).

Source record↗

NASA NTRSDate not supplied

Mitigating Headward Fluid Shifts with Venoconstrictive Thigh Cuffs during Spaceflight

Venoconstrictive thigh cuffs (VTC) are a mechanical countermeasure capable of attenuating the spaceflight induced headward fluid shift, and thus may be a viable spaceflight associated neuro-ocular syndrome (SANS) countermeasure. Crewmembers can use VTC to mitigate the headward fluid shift to aid in adapting to spaceflight. However, data are needed to determine if VTC affect ocular structures. PURPOSE The purpose of this study is to determine the efficacy of long duration use of VTC application to mitigate the spaceflight-induced headward fluid shift. We hypothesize that a VTC countermeasure will temporarily reverse the headward fluid shift and attenuate spaceflight-induced changes of internal jugular vein (IJV) cross-sectional area, IJV pressure, stroke volume, cardiac output, intraocular pressure (IOP), and optic nerve head and retinal morphology. METHODS This study will evaluate the effectiveness of VTC countermeasure application on the headward fluid shift, as well as cardiovascular and ocular variables. VTC during spaceflight will be worn for an extended duration (up to 6 hours) with data collected at three time points (30 minutes, 3 hours, and 6 hours) to characterize the temporal profile of key fluid shift outcome measures of the vascular fluid shift, IOP, and ocular structure changes. Ten astronauts will be recruited to participate and will be studied before and during approximately 180-day International Space Station (ISS) spaceflight missions. Baseline data collection will occur approximately 90-days before launch (Figure). Preflight, each leg of the crewmember will be measured to determine the VTC cuff size and a cuff fit check session will occur prior to the preflight baseline ground imaging to verify the appropriate fit measured via a surface contact pressure. Prior to donning the VTC, baseline measures without VTC will be collected seated, supine, and supine followed by data collection with the VTC. The baseline data collection will include ultrasound (IJV area and pressure, stroke volume and cardiac output), brachial blood pressure and heart rate, optical coherence tomography (OCT) imaging (total retinal thickness and choroid thickness), and IOP. An inflight cuff fit check session, same as the preflight fit check, will occur prior to VTC use on ISS. The inflight VTC experiment will be conducted early (FD45) and late (R-45) to determine if mission duration affects VTC fit and the efficacy of fluid redistribution. A system usability scale comfort questionnaire will be included in each VTC session to capture feedback from crewmembers regarding the comfort and usability of the VTC. SCIENTIFIC & MISSION IMPACT Results will narrow knowledge gaps described in the Human Research Roadmap to mitigate the headward fluid shift during spaceflight and help NASA to 1) determine the efficacy of extended use VTC application to mitigate the spaceflight-induced headward fluid shift and 2) further the understanding of the use of VTC on vascular fluid shifts, IOP, and ocular structure during spaceflight. Supported by NASA Human Research Program Directed Research. Figure. Detailed Testing Schedule. Baseline data collection at L-90 will be performed in a randomized order of position.

J V Jasien↗

DOE OSTI2018

Up-regulation of miR-122 protects against neuronal cell death in ischemic stroke through the heat shock protein 70-dependent NF-κB pathway by targeting FOXO3

Highlights: • miR-122 was decreased in mouse N2A neuroblastoma (N2A) cells after OGD and mouse brain after MCAO. • Gain-of-miR-122 function significantly suppressed OGD- and MCAO-induced injures in vitro and in vivo. • miR-122 was validated to directly bind to the predicted 3′-untranslated region (3′-UTR) of FOXO3. • The inhibitory effects of miR-122 on ischemic injury in vitro and in vivo were overturned by FOXO3 overexpression and miR-122-FOXO3 axis functioned via the heat shock protein 70 (HSP-70)-mediated NF-κB pathway. • miR-122 inhibits ischemic neuronal death through HSP-70-dependent NF-κB pathway by targeting FOXO3. Dysfunction of the microRNA (miRNA) network has been emerging as a main regulator in ischemic stroke. Recently, studies have linked the deregulation of miR-122 to ischemic stroke. However, the specific role and molecular mechanism of miR-122 in ischemic stroke remain to be further investigated. Here, we found that miR-122 was decreased in mouse N2A neuroblastoma (N2A) cells after oxygen-glucose deprivation (OGD) and mouse brain after transient middle cerebral artery occlusion (MCAO). OGD treatment significantly increased N2A cell death and Caspase-3 activity, and decreased Bcl-2 protein expression. In addition, MCAO treatment induced severe mouse brain infarction, mitochondrial reactive oxygen species (ROS) production, and long-term neurological deficit. Gain-of-miR-122 function significantly suppressed OGD- and MCAO-induced injures in vitro and in vivo. Subsequently, miR-122 was validated to directly bind to the predicted 3′-untranslated region (3′-UTR) of FOXO3 gene, and the inhibitory effects of miR-122 on ischemic injury in vitro and in vivo were overturned by FOXO3 overexpression. Moreover, our results further revealed that miR-122-FOXO3 axis functioned via the heat shock protein 70 (HSP-70)-mediated NF-κB pathway. Collectively, our data suggest that miR-122 inhibits ischemic neuronal death through the HSP-70-dependent NF-κB pathway by targeting FOXO3. These findings raise the possibility that this regulatory net may contribute to the pathogenesis of the ischemic brain injury in stroke.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2019

Current Role of the Total Artificial Heart in the Management of Advanced Heart Failure

The total artificial heart (TAH) is a form of mechanical circulatory support that involves resection of the native ventricles followed by placement of a device that can restore total pulmonary and systemic flow. Given the increasing burden of congestive heart failure and cardiovascular disease, the number of people in need of cardiac replacement therapy will continue to grow. Despite aggressive efforts to expand the donor pool, the number of heart transplants in the United States (US) has plateaued at less than 3000 per year. In addition, there is increasing recognition of the long-term complications of current generation left ventricular assist devices such as progressive aortic insufficiency, complications related to blood trauma, and both early and delayed right ventricular failure. These factors may serve to expand the role of the TAH in the treatment of patients with end-stage heart failure particularly if new generation devices are developed that are durable, have an improved safety profile, and are totally implantable. Purpose of Review: To review the role and current evidence of the use of the TAH in the management of advanced heart failure and discuss development of recent TAHs that may have an impact on the field in the near future. Recent Findings: Many patients that receive a heart transplant are bridged with a mechanical support device, most commonly a left ventricular assist device (LVAD). However, there is a small subset of patients with profound biventricular (BV) failure or structural abnormalities that preclude LVAD placement, who will require support with a biventricular assist device (BiVAD) or TAH. There are numerous studies showing the efficacy of the TAH in bridging to transplantation. Also, recent studies have shown equal rates of bridging to transplantation between patients receiving a TAH compared to a BiVAD. However, BiVAD support has a higher incidence of stroke in addition to complications related to the native heart such as arrhythmias and valve dysfunction. Currently, there are multiple new generation artificial hearts in both preclinical development and in clinical trials for both bridge to transplant and destination therapy. Summary: TAH have been shown to be effective for circulatory support in select patients with end-stage heart failure. Current LVADs are associated with significant long-term complications related to retention of the native heart and pump design. Many of these complications may be addressed by the increased use of cardiac replacement therapy, i.e., total artificial hearts. Multiple generations of both pulsatile and advanced design continuous flow TAH are under development which have the potential to expand the role of TAHs.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2018

Custom-Made Endograft for Endovascular Repair of Thoraco-Abdominal Aneurysm and Type B Dissection: Single-Centre Experience

AimsTo report a series of patients treated with the Jotec custom-made endograft for thoraco-abdominal aneurysms and dissections and identify predictive factors for re-intervention.MethodsWe retrospectively analysed 49 patients unsuitable for surgery, treated between 2011 and 2017 (71.3 ± 9.5 years; 15 females). Indications included Crawford type 4 aneurysm in 25 patients, type 3 in 13, type 2 in 4, type 1 in 2 and chronic aneurysmal dilatation of the false lumen following dissection in 5 cases. Mean aneurysm diameter was 58.7 ± 8.4 mm. The study aims were to assess procedural success, complications rate, mortality and long-term follow-up. We also analysed factors that predicted the need for re-intervention.ResultsThe endograft was successfully deployed in all patients, catheterization of the fenestration and/or branches was achieved in 152/156 (97.4%) vessels. Early complications occurred in 10 patients (3 paraplegia, 3 haemorrhages, pancreatitis, aortic rupture, iliac artery rupture, 2 strokes). Thirty-day mortality was 10.2% and 180-day mortality 14.3%; two non procedure related deaths occurred. Mean follow-up was 23.6 ± 29.9 months [range 1–80]. No patients needed surgical explantation or developed significant renal impairment. Endoleak rate was 34.6% and re-intervention rate 9.7%. The aneurysm sac reduced or was stable in 36/49, and enlarged in 9/49 patients prompting re-intervention. Primary, primary-assisted and secondary patency of fenestrations/branches at 80 months was 90, 96 and 100%. Re-intervention was required more frequently in braches than in fenestrations, most commonly the external type branches.ConclusionsThe results of the Jotec endograft are comparable to other devices, with acceptable complication and re-intervention rates. Fenestration and inner-branch should be preferred due to lower re-intervention rates.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2022

Status of LBNF/DUNE near site liquid argon proximity and external cryogenics systems development.

The Deep Underground Neutrino Experiment (DUNE) near site located at Fermilab will host the neutrino beam complex. It includes a high voltage liquid argon time projection chamber located 60-meter underground used as beamline instrumentation. The LAr cryogenic system provided by the Long-Baseline Neutrino Facility (LBNF) regulates thermohydraulic conditions of the membrane cryostat hosting the detector with 285 Ton purified LAr. The purification system uses molecular sieve and copper oxide pellets to manage the argon contamination below 100 ppt (parts per trillion) oxygen equivalent. The detector and its cryogenics are capable to move a stroke of 30 meters on/off beam. The cryogenic system modes of operation include the cryostat pressure test, purge in open loop, detector cooldown, cryostat fill, closed loop purification, liquid empty, and purification system activation/regeneration process. The system design status and schedule, and technical details such as operating modes and interfaces are reported in this paper.

43 PARTICLE ACCELERATORS↗

NASA NTRS2014

Effects of Long Duration Spaceflight on Venous and Arterial Compliance

The visual impairment and intracranial pressure syndrome (VIIP) is a newly described space flight-associated medical condition made up of a constellation of symptoms affecting at least 34% of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures, and is thought to be related to elevated intracranial pressure secondary to space flightinduced cephalad fluid shifts. Loss of visual acuity could be a significant threat to crew health and performance and may be suggestive of other adaptations with implications for years post-flight. Our primary objective is to determine whether vascular compliance is altered by space flight and whether such adaptations are related to the incidence of VIIP. In particular, we will measure ocular parameters and vascular compliance in vessels of the head and neck in astronauts who have no space flight experience, in astronauts before, during, and after space flight, and in bed rest subjects with conditions similar to space flight. Additionally, we will analyze astronaut data from the Lifetime Surveillance of Astronaut Health (LSAH) archive to determine which factors might be predictive of the development of VIIP. The project will be conducted in four separate but related parts. To understand the baseline condition of astronauts without any prior space flight experience, we will study 10 astronauts who have never flown in space by performing a comprehensive evaluation of the vasculature of the head, neck and eyes. Hemodynamic data (stroke volume and blood pressure), ocular (tonometry and ocular ultrasound), venous and arterial parameters will be acquired across a range of tilt angles (20, 10, 0, -10, -20 degrees). Vessels to be studied include the temporal, jugular, and vertebral veins and the cerebral, carotid and vertebral arteries. Ophthalmic data from the annual physical will be obtained through data sharing. To examine the relation between vascular compliance in the head and neck and the development of VIIP after a long duration space flight, we will study 10 astronauts before, during, and after long-duration ISS missions. Pre- and post-flight testing will be identical to that described above. During flight, images of the same vessels of interest will be obtained for later analysis. Ophthalmic data including VIIP scores will be obtained through data sharing from medically-required tests. To investigate the effects of age and elevated sodium intake, two potential contributors to VIIP, we will study 24 men (in two age groups: 25-35 and 45-55) during a 14 day 6deg head-down bed rest, a well-accepted analog of space flight. Standard NASA bed rest conditions will be maintained except for dietary sodium. Sodium intake will be similar to that of ISS astronauts, which is higher than consumed in previous bed rest studies. Pre- and post-bed rest testing procedures will be identical to the testing protocol described above for astronauts. Ophthalmic testing (optical coherence tomography, fundoscopy, and tonometry) will be conducted on the same day that vascular compliance measures are obtained. To identify parameters that may relate to an increase in an astronaut's susceptibility to developing VIIP, we will use data mining techniques to evaluate astronaut data obtained from the LSAH. Medical history, family history, space flight history and its related exposures, and history of high performance jet aircraft exposure will be examined for their potential relationship to ocular data. We hypothesize that the cephalad fluid shift induced by space flight will result in structural and functional adaptations in head and neck vessels leading to decreased vascular compliance and related to the development of VIIP symptoms. Further, although VIIP has not been observed in previous bed rest studies, we hypothesize that an elevated sodium intake will increase the incidence of VIIP symptoms in this space flight analog. Finally, we hypothesize that data mining analyses will reveal relationships between health history, previous exposures (including space flight and high performance aircraft), and the development of VIIP in the astronaut population.

Ribeiro, L. C.↗

NASA NTRS1978

The influence of tortuosity on the spectrum of radiation from lightning return strokes

An investigation was made of the influence of tortuosity on the spectrum of radiation from lightning return strokes. The shape of the spectrum obtained by including effects of tortuosity was in keeping with data: The spectrum had a peak in the correct frequency regime followed by an initial decrease as the inverse of frequency. This spectrum was in better agreement with data than the spectrum predicted by the same model without tortuosity (i.e. the long straight channel), which decays at a rate proportional to 1/v squared.

Levine, D. M.↗