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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

EX4 stabilizes and activates Nrf2 via PKCδ, contributing to the prevention of oxidative stress-induced pancreatic beta cell damage

Oxidative stress in pancreatic beta cells can inhibit insulin secretion and promote apoptotic cell death. Exendin-4 (EX4), a glucagon-like peptide-1 receptor agonist, can suppress beta cell apoptosis, improve beta cell function and protect against oxidative damage. In this study, we investigated the molecular mechanisms for antioxidative effects of EX4 in pancreatic beta cells. INS-1 cells, a rat insulinoma cell line, were pretreated with EX4 and exposed to palmitate or H{sub 2}O{sub 2}. Reactive oxygen species (ROS) production, and glutathione and insulin secretion were measured. The mRNA and protein expression levels of antioxidant genes were examined. The level of nuclear factor erythroid 2-related factor 2 (Nrf2), its binding to antioxidant response element (ARE), and its ubiquination in the presence of EX4 were determined. The Nrf2 signaling pathway was determined using rottlerin (protein kinase [PK]Cδ inhibitor), H89 (PKA inhibitor) and LY294002 (phosphatidylinositide 3-kinase [PI3K] inhibitor). EX4 treatment decreased ROS production, recovered cellular glutathione levels and insulin secretion in the presence of oxidative stress in INS-1 cells. The expression levels of glutamate-cysteine ligase catalytic subunit and heme oxygenase-1 were increased by EX4 treatment. EX4 promoted Nrf2 translocation, ARE binding activity and enhanced stabilization of Nrf2 by inhibition of ubiquitination. Knockdown of Nrf2 abolished the effect of EX4 on increased insulin secretion. Inhibition of PKCδ attenuated Nrf2 translocation and antioxidative gene expression by EX4 treatment. We suggest that EX4 activates and stabilizes Nrf2 through PKCδ activation, contributing to the increase of antioxidant gene expression and consequently improving beta cell function in the presence of oxidative stress. - Highlights: • EX4 protects against oxidative stress-induced pancreatic beta cell dysfunction. • EX4 increases antioxidant gene expression. • Antioxidative effect of EX4 is mediated by Nrf2. • EX4 increases Nrf2 level by stabilizing Nrf2 protein. • EX4 stabilizes Nrf2 by activation of PKCδ.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

[beta subsccript 2]-microglobulin forms three-dimensional domain-swapped amyloid fibrils with disulfide linkages

{beta}{sub 2}-microglobulin ({beta}{sub 2}-m) is the light chain of the type I major histocompatibility complex. It deposits as amyloid fibrils within joints during long-term hemodialysis treatment. Despite the devastating effects of dialysis-related amyloidosis, full understanding of how fibrils form from soluble {beta}{sub 2}-m remains elusive. Here we show that {beta}{sub 2}-m can oligomerize and fibrillize via three-dimensional domain swapping. Isolating a covalently bound, domain-swapped dimer from {beta}{sub 2}-m oligomers on the pathway to fibrils, we were able to determine its crystal structure. The hinge loop that connects the swapped domain to the core domain includes the fibrillizing segment LSFSKD, whose atomic structure we also determined. The LSFSKD structure reveals a class 5 steric zipper, akin to other amyloid spines. The structures of the dimer and the zipper spine fit well into an atomic model for this fibrillar form of {beta}{sub 2}-m, which assembles slowly under physiological conditions.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Design of organic structure directing agents for polymorph A zeolite beta

Zeolite beta is a crystalline material with layer-type faulting. The two end members with perfect crystalline order are beta A and beta B. While zeolite beta in faulted form is a widely used industrial catalyst, additional applications may be possible with the perfect crystalline forms. We here computationally design chemically synthesizable organic structure directing agents that may aid the nucleation and growth of pure zeolite beta A, excluding the competing product zeolite beta B.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Characterization of a new series of non-covalent proteasome inhibitors with exquisite potency and selectivity for the 20S [beta]5-subunit

The mammalian 26S proteasome is a 2500 kDa multi-catalytic complex involved in intracellular protein degradation. We describe the synthesis and properties of a novel series of non-covalent di-peptide inhibitors of the proteasome used on a capped tri-peptide that was first identified by high-throughput screening of a library of approx. 350000 compounds for inhibitors of the ubiquitin-proteasome system in cells. We show that these compounds are entirely selective for the {beta}5 (chymotrypsin-like) site over the {beta}1 (caspase-like) and {beta}2 (trypsin-like) sites of the 20S core particle of the proteasome, and over a panel of less closely related proteases. Compound optimization, guided by X-ray crystallography of the liganded 20S core particle, confirmed their non-covalent binding mode and provided a structural basis for their enhanced in vitro and cellular potencies. We demonstrate that such compounds show low nanomolar IC{sub 50} values for the human 20S {beta}5 site in vitro, and that pharmacological inhibition of this site in cells is sufficient to potently inhibit the degradation of a tetra-ubiquitin-luciferase reporter, activation of NF{Kappa}B (nuclear factor {Kappa}B) in response to TNF-{alpha} (tumor necrosis factor-{alpha}) and the proliferation of cancer cells. Finally, we identified capped di-peptides that show differential selectivity for the {beta}5 site of the constitutively expressed proteasome and immunoproteasome in vitro and in B-cell lymphomas. Collectively, these studies describe the synthesis, activity and binding mode of a new series of non-covalent proteasome inhibitors with unprecedented potency and selectivity for the {beta}5 site, and which can discriminate between the constitutive proteasome and immunoproteasome in vitro and in cells.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Failure of the gross theory of beta decay in neutron deficient nuclei

The neutron deficient isotopes 117-121 Xe, 117-124 Cs, and 122-124 Ba were produced by a beam of 28 Si from the LBNL SuperHILAC on a target of nat Mo. The isotopes were mass separated and their beta decay schemes were measured with a Total Absorption Spectrometer (TAS). The beta strengths derived from these data decreased dramatically to levels above ≈1 MeV for the even-even decays; 3–4 MeV for even-Z, odd-N decays; 4–5 MeV for the odd-Z, even-N decays; and 7–8 MeV for the odd-Z, odd-N decays. The decreasing strength to higher excitation energies in the daughters contradicts the predictions of the Gross Theory of Beta Decay. The integrated beta strengths are instead found to be consistent with shell model predictions where the single-particle beta strengths are divided amoung many low-lying levels. The experimental beta strengths determined here have been used calculate the half-lives of 143 neutron deficient nuclei with Z=51–64 to a precision of 20% with respect to the measured values.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Crystal Structure of Full-length Mycobacterium tuberculosis H37Rv Glycogen Branching Enzyme; Insights of N-Terminal [beta]-Sandwich in Sustrate Specifity and Enzymatic Activity

The open reading frame Rv1326c of Mycobacterium tuberculosis (Mtb) H37Rv encodes for an {alpha}-1,4-glucan branching enzyme (MtbGlgB, EC 2.4.1.18, Uniprot entry Q10625). This enzyme belongs to glycoside hydrolase (GH) family 13 and catalyzes the branching of a linear glucose chain during glycogenesis by cleaving a 1 {yields} 4 bond and making a new 1 {yields} 6 bond. Here, we show the crystal structure of full-length MtbGlgB (MtbGlgBWT) at 2.33-{angstrom} resolution. MtbGlgBWT contains four domains: N1 {beta}-sandwich, N2 {beta}-sandwich, a central ({beta}/{alpha}){sub 8} domain that houses the catalytic site, and a C-terminal {beta}-sandwich. We have assayed the amylase activity with amylose and starch as substrates and the glycogen branching activity using amylose as a substrate for MtbGlgBWT and the N1 domain-deleted (the first 108 residues deleted) Mtb{Delta}108GlgB protein. The N1 {beta}-sandwich, which is formed by the first 105 amino acids and superimposes well with the N2 {beta}-sandwich, is shown to have an influence in substrate binding in the amylase assay. Also, we have checked and shown that several GH13 family inhibitors are ineffective against MtbGlgBWT and Mtb{Delta}108GlgB. We propose a two-step reaction mechanism, for the amylase activity (1 {yields} 4 bond breakage) and isomerization (1 {yields} 6 bond formation), which occurs in the same catalytic pocket. The structural and functional properties of MtbGlgB and Mtb{Delta}108GlgB are compared with those of the N-terminal 112-amino acid-deleted Escherichia coli GlgB (EC{Delta}112GlgB).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Europium and samarium separation using ion exchange between molten salts and beta“-alumina

Here, a new approach to separating europium and samarium using ion exchange reactions between molten salts and a solid electrolyte, beta"-alumina, has been demonstrated. Separations were achieved by both ion exchange of europium and samarium into and out of beta"-alumina. A small separation factor of 1.07 was achieved from the ion exchange of europium into beta"-alumina. A much larger separation was achieved from ion exchange of europium out of beta"-alumina, with noticeable dependencies on the molten salt and experimental parameters (temperature, atmosphere, etc.) used. The highest separation factor achieved was greater than 30. However, the europium extraction efficiency was low. The highest europium extraction efficiency achieved was 51.8% ± 2.6 with a separation factor of 4.70 ± 0.46. The selective ion exchange of europium out of the beta"-alumina material is achieved based upon the higher conductivity of Eu 2+ compared to Ln 3+ (Ln = Eu, Sm) species also present in the beta"-alumina.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The role of proteomics in assessing beta-cell dysfunction and death in type 1 diabetes

Introduction: Type 1 diabetes is characterized by autoimmune destruction of the pancreatic beta cells, resulting in the shortage of insulin and inability to control glycemia. Unfortunately, the process of beta-cell death is poorly understood, and the current best treatment for type 1 diabetes is administration of exogenous insulin. To better understand the process of beta-cell death and to develop new therapies for T1D, there is an urgent need for biomarkers that can reliably predict each stage of the disease. Areas covered: Mass spectrometry-based proteomics and complementary techniques are playing an important role in understanding the processes of the autoimmune response, inflammation and beta-cell death. Mass spectrometry is also a leading technology for the identification of biomarkers. This, and the technical difficulties and new technologies that provide opportunities to characterize small amounts of sample in great depth and to analyze large sample cohorts will be discussed in the present review. Expert opinion: Understanding mechanisms of and discovering biomarkers associated with disease development are interconnected processes that depend on each other to be successful. Ideal biomarkers would be molecules specific to the different stages of the disease process that are released from beta cells to the bloodstream. However, such molecules are likely present in trace amounts in the blood due to the small number of pancreatic beta cells in the human body and the heterogeneity of the target organ and disease process. New and better proteomics technologies will play a major role in achieving a better understanding of the disease and in identifying specific and sensitive biomarkers.

Nakayasu, Ernesto S.↗
DOE OSTI2011

KSTAR Equilibrium Operating Space and Projected Stabilization at High Normalized Beta

Along with an expanded evaluation of the equilibrium operating space of the Korea Superconducting Tokamak Advanced Research, KSTAR, experimental equilibria of the most recent plasma discharges were reconstructed using the EFIT code. In near-circular plasmas created in 2009, equilibria reached a stored energy of 54 kJ with a maximum plasma current of 0.34 MA. Highly shaped plasmas with near double-null configuration in 2010 achieved H-mode with clear edge localized mode (ELM) activity, and transiently reached a stored energy of up to 257 kJ, elongation of 1.96 and normalized beta of 1.3. The plasma current reached 0.7 MA. Projecting active and passive stabilization of global MHD instabilities for operation above the ideal no-wall beta limit using the designed control hardware was also considered. Kinetic modification of the ideal MHD n = 1 stability criterion was computed by the MISK code on KSTAR theoretical equilibria with a plasma current of 2 MA, internal inductance of 0.7 and normalized beta of 4.0 with simple density, temperature and rotation profiles. The steep edge pressure gradient of this equilibrium resulted in the need for significant plasma toroidal rotation to allow thermal particle kinetic resonances to stabilize the resistive wall mode (RWM). The impact of various materials and electrical connections of the passive stabilizing plates on RWM growth rates was analysed, and copper plates reduced the RWM passive growth rate by a factor of 15 compared with stainless steel plates at a normalized beta of 4.4. Computations of active RWM control using the VALEN code showed that the n = 1 mode can be stabilized at normalized beta near the ideal wall limit via control fields produced by the midplane in-vessel control coils (IVCCs) with as low as 0.83kW control power using ideal control system assumptions. The ELM mitigation potential of the IVCC, examined by evaluating the vacuum island overlap created by resonant magnetic perturbations, was analysed using the TRIP3D code. Using a combination of all IVCCs with dominant n = 2 field and upper/lower coils in an even parity configuration, a Chirikov parameter near unity at normalized poloidal flux 0.83, an empirically determined condition for ELM mitigation in DIII-D, was generated in theoretical high-beta equilibria. Chirikov profile optimization was addressed in terms of coil parity and safety factor profile.

Park, Y S↗
DOE OSTI2010

Monte Carlo calculated TG-60 dosimetry parameters for the {beta}{sup -} emitter {sup 153}Sm brachytherapy source

Purpose: The formalism recommended by Task Group 60 (TG-60) of the American Association of Physicists in Medicine (AAPM) is applicable for {beta} sources. Radioactive biocompatible and biodegradable {sup 153}Sm glass seed without encapsulation is a {beta}{sup -} emitter radionuclide with a short half-life and delivers a high dose rate to the tumor in the millimeter range. This study presents the results of Monte Carlo calculations of the dosimetric parameters for the {sup 153}Sm brachytherapy source. Methods: Version 5 of the (MCNP) Monte Carlo radiation transport code was used to calculate two-dimensional dose distributions around the source. The dosimetric parameters of AAPM TG-60 recommendations including the reference dose rate, the radial dose function, the anisotropy function, and the one-dimensional anisotropy function were obtained. Results: The dose rate value at the reference point was estimated to be 9.21{+-}0.6 cGy h{sup -1} {mu}Ci{sup -1}. Due to the low energy beta emitted from {sup 153}Sm sources, the dose fall-off profile is sharper than the other beta emitter sources. The calculated dosimetric parameters in this study are compared to several beta and photon emitting seeds. Conclusions: The results show the advantage of the {sup 153}Sm source in comparison with the other sources because of the rapid dose fall-off of beta ray and high dose rate at the short distances of the seed. The results would be helpful in the development of the radioactive implants using {sup 153}Sm seeds for the brachytherapy treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

SARS-CoV-2 Beta variant infection elicits potent lineage-specific and cross-reactive antibodies

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Beta variant of concern (VOC) resists neutralization by major classes of antibodies from COVID-19 patients and vaccinated individuals. In this study, serum of Beta-infected patients revealed reduced cross-neutralization of wild-type virus. From these patients, we isolated Beta-specific and cross-reactive receptor-binding domain (RBD) antibodies. The Beta-specificity results from recruitment of VOC-specific clonotypes and accommodation of mutations present in Beta and Omicron into a major antibody class that is normally sensitive to these mutations. The Beta-elicited cross-reactive antibodies share genetic and structural features with wild type–elicited antibodies, including a public VH1-58 clonotype that targets the RBD ridge. These findings advance our understanding of the antibody response to SARS-CoV-2 shaped by antigenic drift, with implications for design of next-generation vaccines and therapeutics.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Verification of MCNP5-1.60 and MCNP6-Beta-2 for Criticality Safety Applications

To verify that both MCNP5-1.60 and MCNP6-Beta-2 are performing correctly for criticality safety applications, several suites of verification/validation benchmark problems were run in early 2012. Results from these benchmark suites were compared with results from previously verified versions of MCNP5. The goals of this verification testing were: (1) Verify that MCNP5-1.60 works correctly for nuclear criticality safety applications, producing the same results as for the previous verification performed in 2010; (2) Determine the sensitivity to computer roundoff using different Fortran-90 compilers for building MCNP5 and MCNP6, to support moving to current versions of the compilers; and (3) Verify that MCNP6-Beta-2 works correctly for nuclear criticality safety applications, producing the same results as for MCNP5-1.60. This provides support for eventual migration of users and applications to MCNP6. The current production version of MCNP5 included in the RSICC release package is MCNP5-1.60. This version was first distributed by RSICC in October 2010. While there were subsequent RSICC distributions of the MCNP package in July 2011 and February 2012, no changes were made to MCNP5-1.60. The RSICC release package in February 2012 included both MCNP5-1.60 and the current beta version of MCNP6, MCNP6-Beta-2. MCNP6 is the merger of MCNP5 and MCNPX capabilities. The current release of MCNP6 available from RSICC as of February 2012 is MCNP6-Beta-2. This version includes all of the features for criticality safety calculations that are available in MCNP5-1.60, and many new features largely unrelated to nuclear criticality safety calculations. This release is a 'beta' release to allow intermediate and advanced users to begin testing the merged code in their field of expertise. It should not be used for production calculations.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2018

Study of Reconstructed 39 Ar Beta Decays at the MicroBooNE Detector

In atmospheric argon, 39 Ar beta decays occur at a rate of roughly one Becquerel per kilogram; as a result, large liquid argon time projection chambers (LArTPCs) see plentiful amounts of these decays in each event readout window. These 39 Ar beta decays can provide a variety of different uses in LArTPC experiments. They allow for the study of reconstructing point-like ionization charge deposition in the detector, which is relevant for the reconstruction of supernova neutrino interactions. The point-like topology and well-known energy spectrum of 39 Ar beta decays also provides a unique handle for calibrations. Presented here is the first study of reconstructing 39 Ar beta decays in the MicroBooNE LArTPC. The spectrum of reconstructed electron energies from 39 Ar beta decays, measured using raw TPC waveforms, is found to have a similar end point as the predicted distribution. Additionally, the signal shapes of reconstructed 39 Ar beta decay candidates are used to validate the collection plane wire field response.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Study of Shadowing in Beta-Gamma Coincidence Plots for Radioxenon

This document describes a study of the cause of shadowing observed in certain beta-gamma plots produced with beta-gamma coincidence detectors for detection of radioxenon. Beta-gamma detectors must possess adequate resolution to allow for the metastable isotopes 131m Xe and 133m Xe to be distinguished from each other and from 133 Xe. One effect that can minimize the ability to distinguish the metastables from 133 Xe is the shadowing effect, in which a band of high-energy signal is present in addition to the primary signal. A study was performed to determine the cause of the shadowing, and how to minimize the effect of the shadowing on an individual beta cell. Through this study, it is determined that the shadowing results from a difference in light transmission between the dome and end-cap portions of the beta cell. Consequently, it is not possible to remove the shadowing during the beta cell manufacturing process. The shadowing must be minimized by preferentially matching the light output from the end-cap and dome portion prior to the manufacturing process.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Nuclear Matrix Elements for Neutrinoless Double-Beta Decay

Neutrinoless double-beta decay ($0\nu\beta\beta$) is a rare hypothesised process that, if discovered, would establish that the neutrino is Majorana, that is, it is its own antiparticle. Interpretation of experimental results relies on knowledge of nuclear matrix elements, whose large model uncertainty is the limiting factor in comparing measured (bounds on) half-lives to the neutrino mass. Nuclear effective field theory and lattice QCD have the potential to compute these matrix elements with better control over uncertainties, enhancing the discovery potential of next-generation $0\nu\beta\beta$ experiments. This work will survey various lattice QCD double-beta decay calculations and discuss their implications.

Grebe, Anthony V. [Fermilab] (ORCID:00000003103201↗
DOE OSTI2025

Turbulent Heating in Collisionless Low-beta Plasmas: Imbalance, Landau Damping, and Electron–Ion Energy Partition

An understanding of how turbulent energy is partitioned between ions and electrons in weakly collisional plasmas is crucial for modeling many astrophysical systems. Using theory and simulations of a four-dimensional reduced model of low-beta gyrokinetics (the “Kinetic Reduced Electron Heating Model”), we investigate the dependence of collisionless heating processes on plasma beta and imbalance (normalized cross-helicity). These parameters are important because they control the helicity barrier, the formation of which divides the parameter space into two distinct regimes with remarkably different properties. In the first, at lower beta and/or imbalance, the absence of a helicity barrier allows the cascade of injected power to proceed to small (perpendicular) scales, but its slow cascade rate makes it susceptible to significant electron Landau damping, in some cases leading to a marked steepening of the magnetic spectra on scales above the ion Larmor radius. In the second, at higher beta and/or imbalance, the helicity barrier halts the cascade, confining electron Landau damping to scales above the steep “transition-range” spectral break, resulting in dominant ion heating. We formulate quantitative models of these processes that compare well to simulations in each regime, and combine them with results of previous studies to construct a simple formula for the electron–ion heating ratio as a function of beta and imbalance. This model predicts a “winner takes all” picture of low-beta plasma heating, where a small change in the fluctuations' properties at large scales (the imbalance) can cause a sudden switch between electron and ion heating.

Interplanetary turbulence↗
NASA NTRS1985

From Algol to Beta Lyrae

Recognizing that the structure and evolutionary status of Beta Lyrae are much more complicated than for Algol, some of the problems of revealing its structure are discussed. The best model available at present considers Beta Lyrae as an Algol-type semi-detached system in a phase of fairly rapid mass transfer, i.e., younger than typical Algols. It is concluded that Beta Lyrae is not so special as it appears; some characteristics that are so puzzling in Beta Lyrae already appear in such classical Algols as U Cephei and RW Tauri. The mass-accreting components in these systems are surrounded by a hot, turbulent layer which probably expands and which is the seat of emission lines of fairly high ionization discovered in the far ultraviolet. In Beta Lyrae and the so-called W Serpenis stars, the circumstellar hot turbulent shell is much more extensive and probably also denser - a kind of 'superchromosphere'. In Beta Lyrae, a thick disk probably completely surrounds and hides the accreting star proper.

Plavec, M. J.↗
NASA NTRS1993

Space environment durability of beta cloth in LDEF thermal blankets

Beta cloth performance for use on long-term space vehicles such as Space Station Freedom (S.S. Freedom) requires resistance to the degrading effects of the space environment. The major issues are retention of thermal insulating properties through maintaining optical properties, preserving mechanical integrity, and generating minimal particulates for contamination-sensitive spacecraft surfaces and payloads. The longest in-flight test of beta cloth's durability was on the Long Duration Exposure Facility (LDEF), where it was exposed to the space environment for 68 months. The LDEF contained 57 experiments which further defined the space environment and its effects on spacecraft materials. It was deployed into low-Earth orbit (LEO) in Apr. 1984 and retrieved Jan. 1990 by the space shuttle. Among the 10,000 plus material constituents and samples onboard were thermal control blankets of multilayer insulation with a beta cloth outer cover and Velcro attachments. These blankets were exposed to hard vacuum, thermal cycling, charged particles, meteoroid/debris impacts, ultraviolet (UV) radiation, and atomic oxygen (AO). Of these space environmental exposure elements, AO appears to have had the greatest effect on the beta cloth. The beta cloth analyzed in this report came from the MSFC Experiment S1005 (Transverse Flat-Plate Heat Pipe) tray oriented approximately 22 deg from the leading edge vector of the LDEF satellite. The location of the tray on LDEF and the placement of the beta cloth thermal blankets are shown. The specific space environment exposure conditions for this material are listed.

Linton, Roger C.↗