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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Detection of Airborne Influenza A and SARS-CoV-2 Virus Shedding following Ocular Inoculation of Ferrets

Despite reports of confirmed human infection following ocular exposure with both influenza A virus (IAV) and SARS-CoV-2, the dynamics of virus spread throughout oculonasal tissues and the relative capacity of virus transmission following ocular inoculation remain poorly understood. Furthermore, the impact of exposure route on subsequent release of airborne viral particles into the air has not been examined previously. To assess this, ferrets were inoculated by the ocular route with A(H1N1)pdm09 and A(H7N9) IAVs and two SARS-CoV-2 (early pandemic Washington/1 and Delta variant) viruses. Virus replication was assessed in both respiratory and ocular specimens, and transmission was evaluated in direct contact or respiratory droplet settings. Viral RNA in aerosols shed by inoculated ferrets was quantified with a two-stage cyclone aerosol sampler (National Institute for Occupational Safety and Health [NIOSH]). All IAV and SARS-CoV-2 viruses mounted a productive and transmissible infection in ferrets following ocular inoculation, with peak viral titers and release of virus-laden aerosols from ferrets indistinguishable from those from ferrets inoculated by previously characterized intranasal inoculation methods. Viral RNA was detected in ferret conjunctival washes from all viruses examined, though infectious virus in this specimen was recovered only following IAV inoculation. Low-dose ocular-only aerosol exposure or inhalation aerosol exposure of ferrets to IAV similarly led to productive infection of ferrets and shedding of aerosolized virus. Viral evolution during infection was comparable between all inoculation routes examined. Furthermore, these data support that both IAV and SARS-CoV-2 can establish a high-titer mammalian infection following ocular exposure that is associated with rapid detection of virus-laden aerosols shed by inoculated animals.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1986

Some path-following techniques for solution of nonlinear equations and comparison with parametric differentiation

Some path-following techniques are described and compared with other methods. Use of multipurpose techniques that can be used at more than one stage of the path-following computation results in a system that is relatively simple to understand, program, and use. Comparison of path-following methods with the method of parametric differentiation reveals definite advantages for the path-following methods. The fact that parametric differentiation has found a broader range of applications indicates that path-following methods have been underutilized.

Barger, R. L.↗
NASA NTRS1999

Potential Mechanism Leading to Impaired Thermoregulation Following Microgravity Exposure

Prolonged exposure to microgravity or its analogues impairs thermoregulation in humans evidenced by higher internal temperatures following the exposure during a thermal challenge. Although the mechanism leading to this response has not been clearly delineated, we identified that prolonged head-down tilt (HDT) markedly impairs thermoregulatory reflex control of skin blood flow, as demonstrated by an increased internal temperature threshold for cutaneous vasodilation, and by a reduced slope of the relationship between the elevation in skin blood flow relative to the elevation in internal temperature. Recently, Fortney et al. identified similar responses in two individuals following 115 days of microgravity exposure. One possible mechanism leading to altered cutaneous vasodilation during a thermal challenge following actual or simulated microgravity exposure may be associated with baroreflex-mediated attenuation in the elevation of skin blood flow. During a heat stress the elevation in skin blood flow is accomplished through a combination of increased cutaneous vascular conductance and cardiac output, both of which result in central venous pressure (CVP) decreasing 2-6 mmHg. Reductions in CVP of this magnitude in normothermia decrease muscle blood flow and skin blood flow presumably through unloading the cardiopulmonary baroreceptors. It is unclear whether the reduction in CVP, and accompanying cardiopulmonary baroreceptor unloading, during passive heating buffers the elevation in skin blood flow. That is, would the elevation in skin blood flow be greater if CVP did not decrease, or decreased to a lesser extent during the heat stress? Conversely, if CVP decreased to a greater extend during a thermal challenge following a perturbation such as prolonged HDT, would the elevation in skin blood flow be attenuated during that thermal challenge? Given that prolonged HDT decreases plasma volume and central venous pressure, such a finding would provide a plausible hypothesis to explain why skin blood flow does not increase to the same extent during a heat stress following simulated or actual microgravity exposure. Thus, the purpose of this project was to identify whether cardiopulmonary baroreceptor unloading coincident with heat stress buffers the elevation in skin blood flow.

Crandall, C. G.↗
NASA NTRS1999

Altered Cytokine Production By Specific Human Peripheral Blood Cell Subsets Immediately Following Spaceflight

In this study, we have attempted to combine standard immunological assays with the cellular resolving power of the flow cytometer to positively identify the specific cell types involved in spaceflight-induced immune alterations. We have obtained whole blood samples from 27 astronauts collected at three timepoints (L-10, R+0 and R+3) surrounding four recent space shuttle missions. The duration of these missions ranged from 10 to 18 days. Assays performed included serum/urine cortisol, comprehensive subset phenotyping, assessment of cellular activation markers and intracellular cytokine production following mitogenic stimulation. Absolute levels of peripheral granulocytes were significantly elevated following spaceflight, but the levels of circulating lymphocytes and monocytes were unchanged. Lymphocyte subset analysis demonstrated trends towards a decreased percentage of T cells and an increased percentage of B cells. Nearly all of the astronauts exhibited an increased CD4:CD8 ratio, which was dramatic in some individuals. Assessment of memory (CD45RA+) vs. naive (CD45RO+) CD4+ T cell subsets was more ambiguous, with subjects tending to group more as a flight crew. All subjects from one mission demonstrated an increased CD45RA:CD45RO ratio, while all subjects from another Mission demonstrated a decreased ratio. While no significant trend was seen in the monocyte population as defined by scatter, a decreased percentage of the CD14+ CD16+ monocyte subset was seen following spaceflight in all subjects tested. In general, most of the cellular changes described above which were assessed at R+O and compared to L-10 trended to pre-flight levels by R+3. Although no significant differences were seen in the expression of the cellular activation markers CD69 and CD25 following exposure to microgravity, significant alterations were seen in cytokine production in response to mitogenic activation for specific subsets. T cell (CD3+) production of IL-2 was significantly decreased after at R+O as was IL-2 production by both CD4+ and CD8+ T cell subsets for most subjects. Production of IFN(sub gamma) did not appear to be affected by microgravity exposure in either T cells in general or in the CD8+ T cell subset. There was a spaceflight-induced decrease in IFN(sub gamma) production in the CD4+ T cell subset, however it did not reach statistical significance. Serum and urine stress-hormone analysis indicated significant physiologic stresses in astronauts following spaceflight. In summary, these results demonstrate alterations in the peripheral immune system of astronauts immediately after spaceflight of 10 to 18 days duration and support continued research regarding microgravity and immunology (including in-flight sampling) prior to routine long-term spaceflight for astronauts.

Crucian, Brian E.↗
NASA NTRS2006

Comprehensive Astronaut Immune Assessment Following a Short-Duration Space Flight

Immune system dysregulation has been demonstrated to occur during spaceflight and has the potential to cause serious health risks to crewmembers participating in exploration class missions. As a part of an ongoing NASA flight experiment assessing viral immunity (DSO-500), a generalized immune assessment was performed on 3 crewmembers who participated in the recent STS-114 Space Shuttle mission. The following assays were performed: (1) comprehensive immunophenotype analysis; (2) T cell function/intracellular cytokine profiles; (4) secreted Th1/Th2 cytokine profiles via cytometric bead array. Immunophenotype analysis included a leukocyte differential, lymphocyte subsets, T cell subsets, cytotoxic/effector CD8+ T cells, memory/naive T cell subsets and constitutively activated T cells. Study timepoints were L-180, L-65, L-10, R+0, R+3 and R+14. Detailed data are presented in the poster text. As expected from a limited number of human subjects, data tended to vary with respect to most parameters. Specific post-flight alterations were as follows (subject number in parentheses): Granulocytosis (2/3), reduced NK cells (3/3), elevated CD4/CD8 ratio (3/3), general CD8+ phenotype shift to a less differentiated phenotype (3/3), elevated levels of memory CD4+ T cells (3/3), loss of L-selectin on T cell subsets (3/3), increased levels of activated T cells (2/3), reduced IL-2 producing T cell subsets (3/3), levels of IFNg producing T cells were unchanged. CD8+ T cell expression of the CD69 activation markers following whole blood stimulation with SEA+SEB were dramatically reduced postflight (3/3), whereas other T cell function assessments were largely unchanged. Cytometric bead array assessment of secreted T cell cytokines was performed, following whole blood stimulation with either CD3/CD28 antibodies or PMA+ionomycin for 48 hours. Specific cytokines assessed were IFNg, TNFa, IL-2, IL-4, IL-5, IL-10. Following CD3/CD28 stimulation, all three crewmembers had a mission-associated reduction in the levels of secreted IFNg. One crewmember had a post-flight inversion in the IFNg/IL-10 ratio postflight, which trended back to baseline by R+14. Detailed cytokine data are presented in the poster text. This testing regimen was designed to correlate immunophenotype changes (thought to correspond to specific in-vivo immune responses or pathogenesis), against altered leukocyte function and cytokine profiles. In-flight studies are required to determine if post-flight alterations are reflective of the in-flight condition, or are a response to landing and readaptation.

Crucian, Brian↗
NASA NTRS2010

Aerobic Capacity Following Long Duration International Spaces Station (ISS) Missions: Preliminary Results

Maximum oxygen uptake (VO2max) is reduced immediately following space flights lasting <15 d, but has not been measured following long-duration missions. The purpose of this study is to measure VO2max and maximum work rate (WRmax) data from astronauts following ISS flights (91 to 188 d). Methods: Five astronauts [3 M, 2 F: 47+/-6 yr, 174+/-6 cm, 71.9+/-10.9 kg (mean +/- SD)] have participated in the study. Subjects performed upright cycle exercise tests to symptom-limited maximum. An initial test was done approx.270 d before flight to establish work rates for subsequent tests. Subsequent tests, conducted approx.45 d before flight and repeated on the first or second day (R+1/2) and at approx.10 d (R+10) following landing, consisted of 3 5 min stages designed to elicit 25%, 50%, and 75% of preflight VO2max, followed by 25 W(dot)/min increases. VO2, WR, and heart rate (HR) were measured using the ISS Portable Pulmonary Function System [Damec, Odense, DK]. Descriptive statistics are reported. Results: On R+1/2 mean VO2max decreased compared to preflight (Pre: 2.98+/-0.99, R+1/2: 2.63+/-0.56 L(dot)/min); 4 of 5 subjects demonstrated a loss of > 6%. WRmax also decreased on R+1/2 compared to preflight (Pre: 245+/-69, R+1/2: 210+/-45 W). On R+10, VO2max was 2.86+/-0.62 L(dot)/min, with 2 subjects still demonstrating a loss of > 6% from preflight. WRmax on R+10 was 240+/-49 W. HRmax did not change from pre to post-flight. Conclusions: These preliminary results, from the first 5 of 12 planned subjects of an ongoing ISS study, suggest that the majority of astronauts will experience a decrease in VO2max after long-duration space-flight. Interestingly, the two astronauts with the highest preflight VO2max had the greatest loss on R+1/2, and the astronaut with the lowest preflight VO2max increased by 13%. Thus, maintenance of VO2max may be more difficult in astronauts who have a high aerobic capacity, perhaps requiring more intense in-flight exercise countermeasure prescriptions.

Moore, Alan D.↗
NASA NTRS2010

Bone Density Following Three Years of Recovery from Long-Duration Space-Flight

Bone loss during long-duration space flight is well recognized, but the long-term implications on bone health following return from flight remain unclear. Among US crew who were involved in long-duration missions in space (Mir and ISS), we have previously shown that at approximately 12 months following return, men, but not women, had BMD values at most sites that were still lower than would be expected had they not been exposed to a prolonged period of microgravity. We now extend our observations to 3 years of follow-up post-flight. Using their age, pre-flight BMD and follow-up time, post-flight BMD values for each US crew were predicted based on the model developed from the community sample. We found BMD measures to be either stable or improve by 3 years relative to their immediate post-flight BMD, however only total hip BMD still remains significantly lower than would be expected had they not been exposed to microgravity. Among male US crew, who have had their BMD measured following at least 3 years of recovery post long-duration flight, they continue to have lower BMD at the hip than would be expected, raising potential concerns regarding future hip fracture risk.

Amin, S.↗
DOE OSTI2023

Simulation of the NuScale SMR and Investigation of the Effect of Load-Following on Component Lifetimes

The NuScale SMR has been modelled using the Virtual Environment for Reactor Applications (VERA) multiphysics environment and the results compared with the publicly reported data in the Design Certification Application (DCA). The results show an excellent agreement for the compared axial and radial power distributions, temperature coefficients of reactivity, boron and control rod worths, and fast neutron flux. This NuScale model is then used to investigate the effect of different operational modes on reactor components to determine how flexible load-following operation may affect control rod and reactor pressure vessel (RPV) lifetimes. The control rod degradation is confirmed to primarily affect the silver-indium-cadmium (AIC) rod tip. The degradation rate is observed to follow a non-linear function of core power level where the increase in degradation decreases with insertion depth. For the variation in core power levels expected with current load-following schemes, the total control rod degradation is found to be mild, at 5-10% of usable life per cycle for a reactor operating at <80% power. Nonetheless, this enables load following strategies to be confirmed and/or modified to ensure that control rods do not need to be replaced during the 60+ year life of the reactor. The RPV degradation was found to be almost directly proportional to the core power level and was not overly sensitive to flux shape perturbations. Future work is planned using these damage functions to optimize operation over multiple NuScale SMR units and develop strategies for prognostics and health management.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Rapid recovery of invasive wild pig (Sus scrofa) populations following density reduction

Abstract Trapping is an effective strategy for control of invasive wild pig (Sus scrofa), but eradication of populations via trapping alone typically is impractical throughout much of the species’ introduced range. Consequently, recovery of wild pig populations to pre-trapping levels following control is a major impediment to success of long-term control. In this study, we conducted camera-trap surveys to monitor recovery of two wild pig populations immediately following density reductions achieved via trapping on two sites on the Savannah River Site, SC. We used spatial capture-recapture models to estimate wild pig density during seven 3 week periods spanning 12 months to: (1) determine the time required for populations to recover to pre-trapping levels; and (2) evaluate trends in population growth, density, and distribution during recovery. Recovery of both wild pig populations started immediately after trapping ceased, with populations reaching pre-trapping levels in 3 and 5 months. Threeweek population growth rates for each wild pig population during recovery averaged 1.28 (range = 1.11–1.39 on site 1) and 1.24 (range = 0.64–1.92 on site 2), which corresponded to a 345% and 132% increase in abundance (an increase of 141 and 126 individual wild pigs on site 1 and 2, respectively) of each population by the last survey period. Rapid recovery and growth beyond pre-trapping levels of wild pig populations likely were driven by residual wild pigs not removed by trapping and compensatory reproduction and immigration. Our study is one of the first to provide information on how quickly wild pig populations can recover following overall density reductions of 54–68% and indicates practitioners should be prepared to reinitiate trapping efforts in as little as 3 months to prevent recovery of wild pig populations following control.

Biodiversity & Conservation↗
DOE OSTI2021

Data-driven optimization of mixed-integer bi-level multi-follower integrated planning and scheduling problems under demand uncertainty

The coordination of interconnected elements across the different layers of the supply chain is essential for all industrial processes and the key to optimal decision-making. Yet, the modeling and optimization of such interdependent systems are still burdensome. Here we address the simultaneous modeling and optimization of medium-term planning and short-term scheduling problems under demand uncertainty using mixed-integer bi-level multi-follower programming and data-driven optimization. Bi-level multi-follower programs model the natural hierarchy between different layers of supply chain management holistically, while scenario analysis and data-driven optimization allow us to retrieve the guaranteed feasible solutions of the integrated formulation under various demand considerations. We address the data-driven optimization of this challenging class of problems using the DOMINO framework, which was initially developed to solve single-leader single-follower bi-level optimization problems to guaranteed feasibility. This framework is extended to solve single-leader multi-follower stochastic formulations and its performance is characterized by well-known single and multi-product process scheduling case studies. Through our data-driven algorithmic approach, we present guaranteed feasible solutions to linear and nonlinear mixed-integer bi-level formulations of simultaneous planning and scheduling problems and further characterize the effects of the scheduling level complexity on the solution performance, which spans over several hundred continuous and binary variables, and thousands of constraints.

42 ENGINEERING↗
DOE OSTI2025

Nuclear microreactor transient and load-following control with deep reinforcement learning

The economic feasibility of nuclear microreactors will depend on minimizing operating costs through advancements in autonomous control, especially when these microreactors are operating alongside other types of energy systems (e.g., renewable energy). This study explores the application of deep reinforcement learning (RL) for real-time drum control in microreactors, exploring performance in regard to load-following scenarios. By leveraging a point kinetics model with thermal and xenon feedback, we first establish a baseline using a single-output RL agent, then compare it against a traditional proportional–integral–derivative (PID) controller. This study demonstrates that RL controllers, including both single- and multi-agent RL (MARL) frameworks, can achieve similar or even superior load-following performance as traditional PID control across a range of load-following scenarios. In short transients, the RL agent was able to reduce the tracking error rate in comparison to PID by one half to one third. Over extended 300-minute load-following scenarios in which xenon feedback becomes a dominant factor, PID maintained better accuracy, but RL still remained within a 1% error margin despite being trained only on short-duration scenarios. This highlights RL’s strong ability to generalize and extrapolate to longer, more complex transients, affording substantial reductions in training costs and reduced overfitting. Furthermore, when control was extended to multiple drums, MARL enabled independent drum control as well as maintained reactor symmetry constraints without sacrificing performance---an objective that standard single-agent RL could not learn. We also found that, as increasing levels of Gaussian noise were added to the power measurements, the RL controllers were able to maintain lower error rates than PID, and to do so with at least 10% and upwards of 150% less control effort. These findings illustrate RL's potential for autonomous nuclear reactor control, laying the groundwork for future integration into high-fidelity simulations and experimental validation efforts.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Benzo[$\mathcal{a}$]pyrene toxicokinetics in humans following dietary supplementation with 3,3'-diindolylmethane (DIM) or Brussels sprouts

Utilizing the atto-zeptomole sensitivity of UPLC-accelerator mass spectrometry (UPLC-AMS), we previously demonstrated significant first-pass metabolism following escalating (25–250 ng) oral micro-dosing in humans of [ 14 C]-benzo[a]pyrene ([ 14 C]-BaP). The present study examines the potential for supplementation with Brussels sprouts (BS) or 3,3' -diindolylmethane (DIM) to alter plasma levels of [ 14 C]-BaP and metabolites over a 48-h period following micro-dosing with 50 ng (5.4 nCi) [ 14 C]-BaP. Volunteers were dosed with [ 14 C]-BaP following fourteen days on a cruciferous vegetable restricted diet, or the same diet supplemented for seven days with 50 g of BS or 300 mg of BR-DIM ® prior to dosing. BS or DIM reduced total [ 14 C] recovered from plasma by 56–67% relative to nonintervention. Dietary supplementation with DIM markedly increased T max and reduced C max for [ 14 C]-BaP indicative of slower absorption. Further, both dietary treatments significantly reduced C max values of four downstream BaP metabolites, consistent with delaying BaP absorption. Dietary treatments also appeared to reduce the T 1/2 and the plasma AUC( 0,$\infty$ ) for Unknown Metabolite C, indicating some effect in accelerating clearance of this metabolite. Toxicokinetic constants for other metabolites followed the pattern for [ 14 C]-BaP (metabolite profiles remained relatively consistent) and non-compartmental analysis did not indicate other significant alterations. Significant amounts of metabolites in plasma were at the bay region of [ 14 C]-BaP irrespective of treatment. Although the number of subjects and large interindividual variation are limitations of this study, it represents the first human trial showing dietary intervention altering toxicokinetics of a defined dose of a known human carcinogen.

3,3'-diindolylmethane↗
DOE OSTI2023

A subset of viruses thrives following microbial resuscitation during rewetting of a seasonally dry California grassland soil

Viruses are abundant, ubiquitous members of soil communities that kill microbial cells, but how they respond to perturbation of soil ecosystems is essentially unknown. Here, we investigate lineage-specific virus-host dynamics in grassland soil following “wet-up”, when resident microbes are both resuscitated and lysed after a prolonged dry period. Quantitative isotope tracing, time-resolved metagenomics and viromic analyses indicate that dry soil holds a diverse but low biomass reservoir of virions, of which only a subset thrives following wet-up. Viral richness decreases by 50% within 24 h post wet-up, while viral biomass increases four-fold within one week. Though recent hypotheses suggest lysogeny predominates in soil, our evidence indicates that viruses in lytic cycles dominate the response to wet-up. We estimate that viruses drive a measurable and continuous rate of cell lysis, with up to 46% of microbial death driven by viral lysis one week following wet-up. Thus, viruses contribute to turnover of soil microbial biomass and the widely reported CO 2 efflux following wet-up of seasonally dry soils.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Hydration of α-UO 3 following storage under controlled conditions of temperature and relative humidity

Changes in chemical speciation of uranium oxides following storage under varied conditions of temperature and relative humidity are valuable for characterizing material provenance. In this study, subsamples of high purity α-UO 3 were stored under four sets of controlled conditions of temperature and relative humidity over several years, and then measured periodically for chemical speciation. Powder X-ray diffraction (XRD) analysis and extended X-ray absorption fine structure spectroscopy confirm hydration of α-UO 3 to a schoepite-like end product following storage under each of the varied storage conditions, but the species formed during exposure to the lower relative humidity and lower temperature condition follows different trends from those formed under the other three storage conditions (high relative humidity with high or low temperatures, and low relative humidity with a high temperature). Thermogravimetry coupled with XRD analysis was carried out to distinguish desorption pathways of water from the hydrated end products. Density functional theory calculations discern changes in the structure of α-UO 3 following incorporation of 1, 2 or 3 H 2 O molecules or 1, 2 or 3 OH groups into the orthorhombic lattice, revealing differences in lattice constants, U–O bond lengths, and U–U distances. The collective results from this analysis are in contrast to analogous studies that report that U 3 O 8 is oxidized and hydrated in air during storage under high relative humidity conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Implications of the search for optical counterparts during the second part of the Advanced LIGO’s and Advanced Virgo’s third observing run: lessons learned for future follow-up observations

ABSTRACT Joint multimessenger observations with gravitational waves and electromagnetic (EM) data offer new insights into the astrophysical studies of compact objects. The third Advanced LIGO and Advanced Virgo observing run began on 2019 April 1; during the 11 months of observation, there have been 14 compact binary systems candidates for which at least one component is potentially a neutron star. Although intensive follow-up campaigns involving tens of ground and space-based observatories searched for counterparts, no EM counterpart has been detected. Following on a previous study of the first six months of the campaign, we present in this paper the next five months of the campaign from 2019 October to 2020 March. We highlight two neutron star–black hole candidates (S191205ah and S200105ae), two binary neutron star candidates (S191213g and S200213t), and a binary merger with a possible neutron star and a ‘MassGap’ component, S200115j. Assuming that the gravitational-wave (GW) candidates are of astrophysical origin and their location was covered by optical telescopes, we derive possible constraints on the matter ejected during the events based on the non-detection of counterparts. We find that the follow-up observations during the second half of the third observing run did not meet the necessary sensitivity to constrain the source properties of the potential GW candidate. Consequently, we suggest that different strategies have to be used to allow a better usage of the available telescope time. We examine different choices for follow-up surveys to optimize sky localization coverage versus observational depth to understand the likelihood of counterpart detection.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Long-term follow-up observations of extreme coronal line emitting galaxies

We present new spectroscopic and photometric follow-up observations of the known sample of extreme coronal line-emitting galaxies (ECLEs) identified in the Sloan Digital Sky Survey (SDSS). With these new data, observations of the ECLE sample now span a period of two decades following their initial SDSS detections. We confirm the non-recurrence of the iron coronal line signatures in five of the seven objects, further supporting their identification as the transient light echoes of tidal disruption events (TDEs). Photometric observations of these objects in optical bands show little overall evolution. In contrast, mid-infrared (MIR) observations show ongoing long-term declines consistent with power-law decay. The remaining two objects had been classified as active galactic nuclei (AGNs) with unusually strong coronal lines rather than being TDE related, given the persistence of the coronal lines in earlier follow-up spectra. We confirm this classification, with our spectra continuing to show the presence of strong, unchanged coronal line features and AGN-like MIR colors and behavior. We have constructed spectral templates of both subtypes of ECLE to aid in distinguishing the likely origin of newly discovered ECLEs. We highlight the need for higher cadence, and more rapid, follow-up observations of such objects to better constrain their properties and evolution. We also discuss the relationships between ECLEs, TDEs, and other identified transients having significant MIR variability.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Differential ultrastructural alterations in the Vglut2 glutamatergic input to the substantia nigra pars compacta/pars reticulata following nigrostriatal dopamine loss in a progressive mouse model of Parkinson’s disease

Abstract Loss of nigrostriatal dopamine (DA) in Parkinson's disease results in over‐activation/bursting of the subthalamic nucleus (STN). The STN projects to the substantia nigra (SN) pars compacta (SNpc) and pars reticulata (SNpr). The vesicular glutamate transporter 2 (Vglut2) is localized within at least STN terminals synapsing within the SN, but it is not known if there are differential changes in the Vglut2+ input to the SNpc versus SNpr following DA loss. The goal/rationale of this current study was to determine whether there were differential changes in the density/levels of glutamate immuno‐gold labeling within Vglut2+ nerve terminals synapsing in the SNpc/SNpr and in the proportion of Vglut2+ terminals contacting tyrosine hydroxylase (TH) positively(+) or negatively(−) labeled dendrites following DA loss. Within the SNpc, there was a significant increase (51.3%) in the density of nerve terminal glutamate immuno‐gold labeling within Vglut2+ terminals synapsing on TH(−) dendrites following MPTP versus the vehicle ( VEH ) group. There was a significant decrease (16%) in the percentage of Vglut2+ terminals contacting TH(+) labeled dendrites in the MPTP‐ versus VEH‐treated group within the SNpc. Within the SNpr, there was a significant decrease in the density of glutamate immuno‐gold labeling in Vglut2+ terminals contacting TH(+) (71.5%) and TH(−) (55.5%) labeled dendrites, suggesting an increase in glutamate release. There was no change in the percentage of Vglut2+ terminals contacting TH(+) or TH(−) dendrites in the SNpr. We conclude that there is a differential effect following DA loss on the glutamate input from Vglut2+ terminals synapsing within the SNpr versus SNpc.

Moore, Cynthia↗
DOE OSTI2023

Testing the contribution of dispersal to microbial succession following a wildfire

ABSTRACT Given increased wildfire activity, there is growing interest in understanding the drivers of microbial succession after fire. Dispersal may be especially important to post-fire succession as biotic communities can be more susceptible to invasion following a disturbance. Here, we experimentally manipulated dispersal into disturbed leaf litter communities collected following a wildfire and tracked bacterial and fungal dispersal assemblages over time. We show that the identity and source of microbes immigrating into the soil surface post-fire change across time with seasonal shifts and the reemergence of aboveground vegetation. Further, dispersal significantly contributed to the reassembly of leaf litter microbial communities after the fire, producing an increasingly distinct assembly trajectory. The effect of dispersal on α-diversity and β-diversity was ecosystem dependent but, unexpectedly, influenced bacterial and fungal communities in a similar manner within ecosystems. Collectively, these results demonstrate that dispersal explicitly alters the course of microbial community succession following a wildfire and may impact bacteria and fungi in parallel ways, despite differing in traits expected to alter dispersal patterns. IMPORTANCE Identifying the mechanisms underlying microbial community succession is necessary for predicting how microbial communities, and their functioning, will respond to future environmental change. Dispersal is one mechanism expected to affect microbial succession, yet the difficult nature of manipulating microorganisms in the environment has limited our understanding of its contribution. Using a dispersal exclusion experiment, this study isolates the specific effect of environmental dispersal on bacterial and fungal community assembly over time following a wildfire. The work demonstrates the potential to quantify dispersal impacts on soil microbial communities over time and test how dispersal might further interact with other assembly processes in response to environmental change.

59 BASIC BIOLOGICAL SCIENCES↗