SEARCH · Search NASA
Results for “Clearance”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Enhanced Sustainability in Treatment of Contaminated Metals for Clearance and Recycling - 20290
Cyclife Sweden AB has, for more than 30 years, provided metal treatment services to the domestic and international nuclear industry with the aim of creating value through metal clearance and recycling. These operations are to a large extent based on the concept that the materials, after pre-treatment, including decontamination, will be melted for clearance. During the melting process, some nuclides separate from the metal while the remaining radioactivity becomes fully homogenized in the metal bath and the resulting ingots, along with the samples taken before casting At a time when activities to fight Climate Challenge are in focus, any savings in energy consumption, in addition to the positive environmental effect of recycling metals back to industry, is more than welcome. If the clearance of certain metallic items can be achieved safely, without using melting, it is the environmentally preferred option provided it carries a reasonable cost. It is even better if an object can go through a decontamination and clearance process prior to re-use inside or outside the nuclear sector. Cyclife Sweden is currently investing in a direct clearance process, to be operated in parallel with the melting process. This new process is expected to be fully operational in the late summer of 2020 and includes pre-treatment, decontamination and heavily shielded clearance measurement installations. The treatment will also allow clearance measurements of larger objects without the need for segmentation, along with allowing objects composed of different materials, like electric motors can be accepted for treatment. This paper gives an overview of the circular economy aspects in a nuclear back-end context, the Cyclife approach to further implement a circular economy approach in the processes, Material Acceptance Criteria for treatment, the facility set-up for the new process and how the melting route and the direct route can be combined in an efficient industrial scale process. To put the new capabilities into perspective, the two different treatment and clearance approaches, i.e. direct clearance and melting, are to be compared. (authors)
The effects of food quantity, light, and temperature on clearance rates in freshwater bivalves (Cyrenidae and Unionidae)
Assessing the environmental variables that influence freshwater bivalve filtration activity is key to better understand the functioning of stream ecosystems. Here, the effects of light (0 ± 0 µmol m –2 s –1 and 19 ± 2 µmol m –2 s –1 ) and temperature (10, 15, 20 and 25°C) on the clearance rates of two bivalve species: the Asian clam Corbicula fluminea (Cyrenidae) and pocketbook Lampsilis ovata (Unionidae) were assessed under controlled laboratory conditions at two different concentrations of algal food (i.e., 10,000 cells ml –1 and 100,000 cells ml –1 ). Clearance rates for C. fluminea varied from 0 to 491 ml g –1 h –1 , while the observed range for L. ovata was 0 to 905 ml g –1 h –1 . We found that the relative contribution of the tested variables was species-dependent. While temperature plays a major role in the clearance rates of C. fluminea , food concentration was the most significant variable in the clearance rate of L. ovata . Our results confirm the complex interactions between abiotic and biotic factors in freshwater bivalve filtration activity. Overall, clearance rates are highly variable especially in C. fluminea and presumably regulated by other untested factors suggesting high plasticity in filtration.
Clearance Tracker
The manual process of managing security clearance was cumbersome and inefficient, involving the emailing of a fillable PDF from person to person. There was no visibility into the progress of a clearance submission. Clearance Tracker provides an automated workflow with data validation and notifications to manage the clearance process. The automated workflow routes notifications to individuals when their input is required. All participants can track the progress of clearance requests.
Independent Verification Plan for Clearance of Real Property of the Operation Roller Coaster Sites
The U.S. Department of Energy (DOE) is pursuing release of the Operation Roller Coaster sites under DOE O 458.1, “Radiation Protection of the Public and the Environment.” The requirements for clearance and release of property under DOE O 458.1 are implemented when DOE intends to facilitate transfer of responsibility or control of real property from DOE. DOE O 458.1 prescribes that all radiological monitoring or surveys performed in support of clearance of property must use methods such as the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) method or other methods approved by DOE. DOE O 458.1 requires an Independent Verification for the clearance of real property. This Independent Verification Plan outlines the process for validating the method and implementation of the MARRSIM process for release of the Operation Roller Coaster sites.
Independent Verification Report for Clearance Operation Roller Coaster Sites
The U.S. Department of Energy (DOE) is pursuing clearance of the Operation Roller Coaster sites under DOE O 458.1, Radiation Protection of the Public and the Environment. The clearance of property requirements in DOE O 458.1 must be implemented when DOE intends to facilitate future transfers of responsibility/control of real property. DOE O 458.1 prescribes that all radiological monitoring or surveys performed in support of clearance of property must use methods such as the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) or other methods approved by DOE. MARSSIM recommends using a series of surveys for collecting information required to demonstrate compliance. These surveys form the Radiation Survey and Site Investigation (RSSI) Process.
Modeling hepatitis C virus kinetics during liver transplantation highlights the role of the liver in virus clearance
While the liver, specifically hepatocytes, are widely accepted as the main source of hepatitis C virus (HCV) production, the role of the liver/hepatocytes in clearance of circulating HCV remains unknown. Frequent HCV kinetic data were recorded and mathematically modeled from five liver transplant patients throughout the anhepatic (absence of liver) phase and for 4 hr post-reperfusion. During the anhepatic phase, HCV remained at pre-anhepatic levels (n = 3) or declined (n = 2) with t 1/2 ~1 hr. Immediately post-reperfusion, virus declined in a biphasic manner in four patients consisting of a rapid decline (t 1/2 = 5 min) followed by a slower decline (t 1/2 = 67 min). Consistent with the majority of patients in the anhepatic phase, when we monitored HCV clearance at 37°C from culture medium in the absence/presence of chronically infected hepatoma cells that were inhibited from secreting HCV, the HCV t 1/2 in cell culture was longer in the absence of chronically HCV-infected cells. The results suggest that the liver plays a major role in the clearance of circulating HCV and that hepatocytes may be involved.
Modeling suggests SARS-CoV-2 rebound after nirmatrelvir-ritonavir treatment is driven by target cell preservation coupled with incomplete viral clearance
In a subset of SARS-CoV-2-infected individuals treated with the antiviral nirmatrelvir-ritonavir, the virus rebounds following treatment. The mechanisms driving this rebound are not well understood. We used a mathematical model to describe the longitudinal viral load dynamics of 51 individuals treated with nirmatrelvir-ritonavir, 20 of whom rebounded. Target cell preservation, either by a robust innate immune response or initiation of N-R near the time of symptom onset, coupled with incomplete viral clearance, appears to be the main factor leading to viral rebound. Moreover, the occurrence of viral rebound is likely influenced by the time of treatment initiation relative to the progression of the infection, with earlier treatments leading to a higher chance of rebound. A comparison with an untreated cohort suggests that early treatments with nirmatrelvir-ritonavir may be associated with a delay in the onset of an adaptive immune response. Nevertheless, our model demonstrates that extending the course of nirmatrelvir-ritonavir treatment to a 10-day regimen may greatly diminish the chance of rebound in people with mild-to-moderate COVID-19 and who are at high risk of progression to severe disease. Altogether, our results suggest that in some individuals, a standard 5-day course of nirmatrelvir-ritonavir starting around the time of symptom onset may not completely eliminate the virus. Thus, after treatment ends, the virus can rebound if an effective adaptive immune response has not fully developed. These findings on the role of target cell preservation and incomplete viral clearance also offer a possible explanation for viral rebounds following other antiviral treatments for SARS-CoV-2.
Clearance rates of freshwater bivalves Corbicula fluminea and Utterbackia imbecillis in the presence and absence of light
Light affects bivalve behavior and gaping activity, but its potential effects on bivalve filtration remain poorly investigated. In this paper, clearance rates of two bivalve species: the Asian clam, Corbicula fluminea and the paper pondshell, Utterbackia imbecillis, were assessed in light (6.5 ± 0.5 µmol m -2 s -1 ) and dark (0.0 µmol m -2 s -1 ) conditions. We found that clearance rates remained similar between C. fluminea (50 ± 18 mL g -1 h -1 ) and U. imbecillis (41 ± 10 mL g -1 h -1 ) during light conditions. However, C. fluminea (110 ± 15 mL g -1 h -1 ) filtered significantly faster than U. imbecillis (24 ± 6 mL g -1 h -1 ) in the dark condition (p < 0.05). The results indicated that light might affect the filtration activity in freshwater bivalves differently, depending on species.
Apolipoprotein A5 reduces clearance of VLDL by altering apolipoprotein E content
Apolipoprotein A-V (APOA5) is a critical regulator of circulating triglyceride (TG) levels. Its deletion leads to elevated plasma TG concentrations by altering the metabolism of very low-density lipoprotein (VLDL) particles in vivo. One way APOA5 exerts its effects is through modulation of lipoprotein lipase (LPL) activity, specifically by disrupting inhibitory interactions between LPL and angiopoietin-like proteins (ANGPTLs). However, the impact of APOA5 on VLDL composition and its potential to alter VLDL metabolism in other ways remains poorly understood. To address this, we investigated the influence of APOA5 on the VLDL proteome, LPL activation, and hepatic remnant uptake. Using VLDL from Apoa5 knockout (KO) and wild-type (WT) mice, we found no evidence that APOA5 directly enhances LPL activity in purified or plasma systems. However, VLDL from Apoa5 K mice was cleared significantly more slowly by cultured hepatocytes. Proteomics experiments from two independent laboratories identified consistent depletion of 17 proteins involved in lipoprotein metabolism, inflammation, and immune response in Apoa5 KO VLDL, including APOE and serum amyloid A1 (SAA1). Remarkably, reintroduction of recombinant mouse APOA5 to the KO plasma partially restored the WT VLDL proteome, including APOE, and normalized VLDL uptake by hepatocytes without altering LPL lipolysis. These findings reveal that APOA5 influences hepatic clearance of VLDL remnants by modulating particle composition, particularly APOE content. This study expands the functional scope of APOA5 in TG metabolism and underscores its role in VLDL remodeling and remnant clearance, offering new insights with implications for understanding hypertriglyceridemia and its roles in inflammation and immune response.
Surface chemistry-mediated modulation of adsorbed albumin folding state specifies nanocarrier clearance by distinct macrophage subsets
Controlling nanocarrier interactions with the immune system requires a thorough understanding of the surface properties that modulate protein adsorption in biological fluids, since the resulting protein corona redefines cellular interactions with nanocarrier surfaces. Albumin is initially one of the dominant proteins to adsorb to nanocarrier surfaces, a process that is considered benign or beneficial by minimizing opsonization or inflammation. Here, we demonstrate the surface chemistry of a model nanocarrier can be engineered to stabilize or denature the three-dimensional conformation of adsorbed albumin, which respectively promotes evasion or non-specific clearance in vivo. Interestingly, certain common chemistries that have long been considered to convey stealth properties denature albumin to promote nanocarrier recognition by macrophage class A1 scavenger receptors, providing a means for their eventual removal from systemic circulation. We establish that the surface chemistry of nanocarriers can be specified to modulate adsorbed albumin structure and thereby tune clearance by macrophage scavenger receptors.
‘Spokesperson for everyone at the Laboratory who believed in Oppenheimer’ Los Alamos physicist Fred Ribe’s 1954 petition protested former Lab Director’s revoked clearance
In 1953, J. Robert Oppenheimer received an ultimatum. The Atomic Energy Commission (AEC) sent the "father of the atomic bomb" and former Los Alamos Director a letter outlining two options: give up his Q clearance and role as advisor or appear before a board to prove that he wasn’t a threat to national security. Oppenheimer chose the latter. The ensuing saga that unfolded throughout 1954 peaked with a four-week, closed-door hearing in April and May after which Oppenheimer’s security clearance was formally revoked. The long, complex affair consisted of national security concerns, a tangle of questionable charges, divided opinions, loyalties, egos, and vendettas. AEC Chairman Lewis L. Strauss and Oppenheimer were at the center of events, though an important part of the historical record is Fred L. Ribe and the 493 other Los Alamos scientists who risked harming their careers to protest Oppenheimer’s ordeal. Ribe wrote a one-page letter, signed by his colleagues, to President Dwight Eisenhower and the AEC commissioners “objecting the decision and the grounds for it” as Ribe later wrote. This petition – and Strauss’s written response – were donated by Ribe and are part of the unclassified historical collections in the National Security Research Center, which is the Lab’s classified library.
Scavenger receptor MARCO contributes to macrophage phagocytosis and clearance of tumor cells
Highlights: • The MARCO receptor on macrophages was positively correlated with the ability to phagocyte tumor cells. • Macrophage MARCO affects cytoskeleton rearrangement and pseudopodia formation through the SYK-PI3K-Rac1 pathway. • Integrin is the ligand of MARCO on the tumor cells. Macrophage receptor with collagenous structure (MARCO) is a member of the class A scavenger receptor family which is expressed on the cell surface of macrophages. It is well known that MARCO avidly binds to unopsonized pathogens, leading to its ingestion by macrophages. However, the role of MARCO in the recognition and phagocytosis of tumor cells by macrophages remains poorly understood. In this study, we used lentiviral technology to knockdown and overexpress MARCO and investigated the ability of macrophages to phagocytose tumor cells. Our results showed that MARCO expression was correlated with the ability of macrophages to carry on phagocytosis. MARCO knockdown led to significant decreases in the number of engulfment pseudopodia of macrophages and inhibition of the phagocytosis of tumor cells. On the other hand, MARCO overexpression elevated activity of SYK, PI3K and Rac1 in macrophages, which led to changes in macrophage morphology and enhanced phagocytosis by promoting formation of stress fibers and pseudopodia. By Co-IP analysis we showed that MARCO directly binds to the β5 integrin of SL4 tumor cells. In summary, these results demonstrated the important role for MARCO in demonstrated tumor cells uptake and clearance by macrophages.
A Methodology for Measuring Blade Clearance on an Operating Utility-Scale Wind Turbine
This report describes the deployment of eleven laser sensors to measure the clearance between blades and tower in a 1.5-MW wind turbine whose rotor was mounted first in upwind and then in downwind configurations. The experimental recordings are compared to the numerical predictions generated by an aeroservoelastic model of the turbine. Good agreement is found between the two datasets, although discrepancies up to 30~cm are observed. The sources of this error are discussed. This methodology is found to be a valuable resource for the validation of the numerical predictions of the flapwise deflections of wind turbine blades. The accurate prediction of these deflections is increasingly important as wind turbines grow in size and become increasingly flexible.
Comprehensive Security Briefing for New Clearance Holders [Slides]
Clearance holders are required to complete annual security training.
J. Robert Oppenheimer: The Atomic Energy Commission and His Security Clearance, Selected Documents
On April 14, 1954, Laboratory employees were formally notified by a “Special Bulletin to All Employees” (Appendix A) that the Atomic Energy Commission had convened a Personnel Security Board, at the request of J. Robert Oppenheimer, to investigate “substantial derogatory information” about their former director. Long on procedural detail and short on specifics, the Bulletin served primarily as an announcement that “A board was accordingly established for the purpose of hearing the case and advising the Commission as to whether or not suspension of clearance of Dr. Oppenheimer should be made permanent.”
The autophagy receptor NBR1 directs the clearance of photodamaged chloroplasts
The ubiquitin-binding NBR1 autophagy receptor plays a prominent role in recognizing ubiquitylated protein aggregates for vacuolar degradation by macroautophagy. Here, we show that upon exposing Arabidopsis plants to intense light, NBR1 associates with photodamaged chloroplasts independently of ATG7, a core component of the canonical autophagy machinery. NBR1 coats both the surface and interior of chloroplasts, which is then followed by direct engulfment of the organelles into the central vacuole via a microautophagy-type process. The relocalization of NBR1 into chloroplasts does not require the chloroplast translocon complexes embedded in the envelope but is instead greatly enhanced by removing the self-oligomerization mPB1 domain of NBR1. The delivery of NBR1-decorated chloroplasts into vacuoles depends on the ubiquitin-binding UBA2 domain of NBR1 but is independent of the ubiquitin E3 ligases SP1 and PUB4, known to direct the ubiquitylation of chloroplast surface proteins. Compared to wild-type plants, nbr1 mutants have altered levels of a subset of chloroplast proteins and display abnormal chloroplast density and sizes upon high light exposure. We postulate that, as photodamaged chloroplasts lose envelope integrity, cytosolic ligases reach the chloroplast interior to ubiquitylate thylakoid and stroma proteins which are then recognized by NBR1 for autophagic clearance. This study uncovers a new function of NBR1 in the degradation of damaged chloroplasts by microautophagy.
Extracellular matrix modulates T cell clearance of malignant cells in vitro
Not Available