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Results for “LU factorization”

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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Suppression of vapor cell temperature error for spin-exchange-relaxation-free magnetometer

This paper presents a method to reduce the vapor cell temperature error of the spin-exchange-relaxation-free (SERF) magnetometer. The fluctuation of cell temperature can induce variations of the optical rotation angle, resulting in a scale factor error of the SERF magnetometer. In order to suppress this error, we employ the variation of the probe beam absorption to offset the variation of the optical rotation angle. The theoretical discussion of our method indicates that the scale factor error introduced by the fluctuation of the cell temperature could be suppressed by setting the optical depth close to one. In our experiment, we adjust the probe frequency to obtain various optical depths and then measure the variation of scale factor with respect to the corresponding cell temperature changes. Our experimental results show a good agreement with our theoretical analysis. Under our experimental condition, the error has been reduced significantly compared with those when the probe wavelength is adjusted to maximize the probe signal. The cost of this method is the reduction of the scale factor of the magnetometer. However, according to our analysis, it only has minor effect on the sensitivity under proper operating parameters.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Ultrafast spontaneous emission modulation of graphene quantum dots interacting with Ag nanoparticles in solution

We investigated the strong interaction between graphene quantum dots and silver nanoparticles in solution using time-resolved photoluminescence techniques. In solution, the silver nanoparticles are surrounded by graphene quantum dots and interacted with graphene quantum dots through exciton-plasmon coupling. An ultrafast spontaneous emission process (lifetime 27 ps) was observed in such a mixed solution. This ultrafast lifetime corresponds to the emission rate exceeding 35 GHz, with the purcell enhancement by a factor of ∼12. These experiment results pave the way for the realization of future high speed light sources applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Nanostructured crystals of Sr{sub 1-x}R{sub x}F{sub 2+x} fluorite phases and their ordering: 6. Microindentation analysis of crystals

Hardness, crack resistance, brittleness, and effective fracture energy have been studied for crystals of 24 fluorite phases Sr{sub 1-x}R{sub x}F{sub 2+x} (R are 14 rare earth elements (REEs); 0 < x {<=} 0.5) and SrF2 grown by the Bridgman method from a melt. These characteristics change nonlinearly with an increase in the REE content for Sr{sub 1-x}R{sub x}F{sub 2+x} (0 < x {<=} 0.5) with R = La, Nd, Sm, Gd, and Lu; it is maximum in the range x < 0.1 for all REEs. The changes in a number of REEs have been traced for an isoconcentration series of Sr{sub 0.90}R{sub 0.10}F{sub 2.10} crystals (R = La, Nd, Sm, Gd, Ho, Er-Lu, or Y) and crystals (similar in composition) with R = Tb and Dy. The hardness of Sr{sub 1-x}R{sub x}F{sub 2+x} crystals is higher by a factor of {approx}2-3 than that of SrF2. The effect of decrease in microstresses in SrF{sub 2} crystals is confirmed by the isomorphic introduction of R{sup 3+} ions into this crystalline matrix.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

A Life Cycle Analysis of Refinery Fuel Products Air Emissions Using Refinery Emissions Inventory Data

With the transportation sector being a major source of air pollutant emissions, this study seeks to evaluate criteria pollutant emissions associated with the use of petroleum fuels in vehicles using the GREET® (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) well-to-wheel model. The life cycle of petroleum fuels includes the major stages of crude recovery, crude transportation, crude refining, fuel distribution and fuel combustion (vehicle operation). This study focuses on quantifying refinery emissions, in terms of both refinery throughput and various refinery fuel products, by matching a refinery emissions inventory dataset with refinery operation information, at various levels (national, regional, facility, and process unit). The refinery emissions in terms refinery throughput (per refinery crude input, in g/mmbtu crude) are developed at a regional level for various Petroleum Administration for Defense Districts (PADD), and also aggregated at the national level. To allocate refinery emissions to refinery products, a methodology is developed using a refinery operation optimization Linear Programming (LP) model for individual refineries. The results from individual refinery facilities are then aggregated to obtain statistical national average (capacity weighted) emissions for each product. Because refineries vary by complexity of operation, configuration, crude quality, and product slate, the derived emissions demonstrate large variation for each product and per unit of crude input. Relative to previous estimates used in the GREET model, the present research shows reductions in refinery (and life cycle) emissions for most criteria pollutants. The reduction is especially significant for sulfur dioxide (SOx) emissions.

Allocation↗
DOE OSTI2021

MUSTN1 is an indispensable factor in the proliferation, differentiation and apoptosis of skeletal muscle satellite cells in chicken

The yield and quality of the skeletal muscle are important economic traits in livestock and poultry production. The musculoskeletal embryonic nuclear protein 1 (MUSTN1) gene has been shown to be associated with embryonic development, postnatal growth, bone and skeletal muscle regeneration; however, its function in the skeletal muscle development of chicken remains unclear. Therefore, in this study, we observed that the expression level of MUSTN1 increased in conjunction with the proliferation of chicken skeletal muscle satellite cells (SMSCs). Knockdown of MUSTN1 in SMSCs downregulated the expression of cell proliferation genes as Pax7, CDK-2 and differentiation-relate genes including MyoD, MyoG, MyHC and MyH1B, whereas it upregulates the expression of cell apoptosis gene (Caspase-3) (P < 0.05). However, the combined analysis of CCK-8 and EdU showed that the cell vitality and EdU-positive cells of the si-MUSTN1 transfected group were significantly lower than those of the negative siRNA group (P < 0.05). In addition, the knockdown of MUSTN1 significantly increased the cell population in the G0/G1 phase and significantly decreased the cell population in the G2/M phase (P < 0.05), whereas the overexpression of MUSTN1 showed opposite effect. Taken together, our findings indicates that MUSTN1 is an important molecular factor that is responsible for regulating muscle growth and development in chickens, particularly, proliferation and differentiation of SMSCs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

New Insights into the Instability of Discharge Products in Na–O 2 Batteries

Sodium–oxygen batteries currently stimulate extensive research due to their high theoretical energy density and improved operational stability when compared to lithium–oxygen batteries. Cell stability, however, needs to be demonstrated also under resting conditions before future implementation of these batteries. In this work we analyze the effect of resting periods on the stability of the sodium superoxide (NaO 2 ) discharge product. The instability of NaO 2 in the cell environment is demonstrated leading to the evolution of oxygen during the resting period and the decrease of the cell efficiency. In addition, migration of the superoxide anion (O2–) in the electrolyte is observed and demonstrated to be an important factor affecting Coulombic efficiency.

25 ENERGY STORAGE↗
DOE OSTI2013

Wogonin inhibits tumor angiogenesis via degradation of HIF-1α protein

Wogonin, a plant-derived flavone, has been shown recently to have antitumor effects. However, the mechanisms that wogonin inhibits tumor angiogenesis are not well known. In this study, we investigated the effects of wogonin on expression of hypoxia-inducible factor-1α (HIF-1α) and secretion of vascular endothelial growth factor (VEGF) in tumor cells. We found that wogonin decreased the expression of HIF-1α by affecting its stability and reduced the secretion of VEGF, which suppressed angiogenesis in cancer. Wogonin promoted the degradation of HIF-1α by increasing its prolyl hydroxylation, which depended on prolyl hydroxylase (PHD) and the von Hippel–Lindau tumor suppressor (VHL). Intriguingly, wogonin impeded the binding between heat-shock protein 90 (Hsp90) and HIF-1α. In addition, wogonin down-regulated the Hsp90 client proteins EGFR, Cdk4 and survivin, but did not affect the level of Hsp90. Wogonin also increased ubiquitination of HIF-1α and promoted its degradation in proteasome. We also found that wogonin could inhibit nuclear translocation of HIF-1α. Electrophoresis mobility shift assay (EMSA) showed that wogonin decreased the binding activity of exogenous consensus DNA oligonucleotide with HIF-1α in nuclear extracts from MCF-7 cells. Chromatin immunoprecipitation (ChIP) assay also revealed that HIF-1α directly binded to endogenous hypoxia-responsive element (HRE) and this binding was significantly decreased in MCF-7 cells treated with wogonin. Preliminary results indicated in vivo activity of wogonin against xenograft-induced angiogenesis in nude mice. Taken together, the results suggested that wogonin was a potent inhibitor of HIF-1α and provided a new insight into the mechanisms of wogonin against cancers. - Highlights: • Wogonin is an all around inhibitor of VEGF signaling. • We firstly demonstrate that wogonin inhibits secretion of VEGF by decreasing HIF-1α. • Wogonin enhances PDH and VHL expression and inhibits Hsp90 function. • Wogonin decreases HIF-1α nuclear import and binding to DNA. • Wogonin may be a potent HIF-1α inhibitor for cancer therapeutics in the future.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

The structural properties of InGaN alloys and the interdependence on the thermoelectric behavior

The III-Nitrides are promising candidate for high efficiency thermoelectric (TE) materials and devices due to their unique features which includes high thermal stability. A systematic study of the room temperature TE properties of metalorganic chemical vapor deposition grown In{sub x}Ga{sub 1-x}N were investigated for x = 0.07 to 0.24. This paper investigated the role of indium composition on the TE properties of InGaN alloys in particular the structural properties for homogenous material that did not show significant phase separation. The highest Seebeck and power factor values of 507 μV K{sup −1} and 21.84 × 10{sup −4} Wm{sup −1}K{sup −1} were observed, respectively for In{sub 0.07}Ga{sub 0.93}N at room temperature. The highest value of figure-of-merit (ZT) was calculated to be 0.072 for In{sub 0.20}Ga{sub 0.80}N alloy at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Investigation of upconversion and downconversion fluorescence emissions from β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal disk system

Graphical abstract: Well-defined β-NaLn1F4:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal thin disks with a simple and user-friendly hydrothermal approach by using sodium citrate as a shape modifier. Much stronger UC and DC fluorescence emissions were observed in NaLuF{sub 4}-based hexagonal disks than that for NaYF{sub 4} counterparts. The strength of hypersensitive transitions is mainly attributed to the decrease of local symmetry Ln-F bond lengths in β-NaLuF{sub 4}. It will show a great potential in improving near-infrared conversion efficiency of silicon solar cells and removable sub-micro luminescent platforms. - Highlights: • Regular hexagonal disks (NaLnF{sub 4}) were synthesized by a simple hydrothermal method. • Much stronger UC and DC emissions were observed in NaLuF{sub 4}-based disks. • Stronger fluorescence emissions in NaLuF{sub 4}-based disks were explained reasonably. • NaLuF{sub 4}-based disks can act as a removable luminescent platform for nano-assembly. • NaLuF{sub 4}-based disks can be applied in improving efficiency of solar cells. - Abstract: Uniform hexagonal β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) disks were synthesized with hydrothermal method in which the sodium citrate was used as a shape modifier. The experimental observation indicated that both upconversion and downconversion fluorescence emissions were significantly stronger in β-NaLuF{sub 4} than that for β-NaYF{sub 4}. It was found that the stronger hypersensitive transitions were mainly due to the increase of J–O parameter (Ω{sub 2}) in β-NaLuF{sub 4} host, while the stronger insensitive transitions were mainly caused by the stronger overlap of electron cloud that was induced by the decrease of Ln-F bond lengths. Additionally, the larger absorption strength in the near-infrared region is another important factor for the stronger fluorescence emissions. The current research has a great potential in improving near-infrared conversion efficiency of silicon solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Overexpression of a novel transcriptional repressor GmMYB3a negatively regulates salt–alkali tolerance and stress-related genes in soybean

Highlights: • We identified and characterized GmMYB3a of R2R3 myeloblastosis repressor family. • GmMYB3a is induced by various abiotic stresses. • For this study, we used a transgenic soybean over-expressing GmMYB3a. • We evaluated the photosynthesis index under salt-alkali treatments. • GmMYB3a was found to negatively affect the response of plants to salt stress. Myeloblastosis (MYB) transcription factor (TF) plays a positive role in the growth and stress response of plants; however, information on the functions of MYB repressors in soybean is limited. In the present study, the gene GmMYB3a was identified and characterized as a member of the R2R3 MYB repressor family, which is induced by various abiotic stresses. To understand the functions of GmMYB3a, a transgenic soybean over-expressing GmMYB3a was obtained and the photosynthetic index under salt–alkali treatments was evaluated. The transgenic line exhibited a series of negative regulation relative to the wild-type control. Quantitative real time polymerase chain reaction revealed that the physiological parameters, including soluble sugar, free proline, and chlorophyll contents; and photosynthetic rate decreased in the transgenic plants. Furthermore, GmMYB3a overexpression down-regulated a set of key genes associated with plant defense signal pathways. These finding suggest that GmMYB3a negatively affects the response of plants to salt stress.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Ultrafine Interwoven Dendritic Cu 2 Se/CuFeSe 2 Composites with Enhanced Thermoelectric Performance

As an effort to develop high-performance and stable copper chalcogenide thermoelectrics, several (1-x)Cu 2 Se/(x)CuFeSe 2 composites were successfully synthesized via a one-step solid-state transformation of CuSe 2 template. Uniform ultrafine dendritic structures consisting of interweaving Cu 2 Se and CuFeSe 2 nanofibers were observed in samples with low Fe content (0.05 ≤ x ≤ 0.1). Increasing the Fe content to x = 0.5 led to phase segregation into Cu 2 Se-rich region with embedded CuFeSe 2 fine structures interwoven with CuFeSe 2 -rich region containing Cu 2 Se nanofibers. The formation of such an entwined dendritic structure is believed to arise from the temperature-dependent solubility of CuFeSe 2 in the Cu 2 Se matrix. The dynamic dissolution of CuFeSe 2 into the Cu 2 Se at high temperatures leads to temperature-dependent doping of the Cu 2 Se matrix, enabling drastic enhancements of thermoelectric power factor at high temperatures. As a result, such a strategy is expected to be a powerful tool for properties modulation in thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Mitigation of nitrogen vacancy photoluminescence quenching from material integration for quantum sensing

The nitrogen-vacancy (NV) color center in diamond has demonstrated great promise in a wide range of quantum sensing. Recently, there have been a series of proposals and experiments using NV centers to detect spin noise of quantum materials near the diamond surface. This is a rich complex area of study with novel nano-magnetism and electronic behavior, that the NV center would be ideal for sensing. However, due to the electronic properties of the NV itself and its host material, getting high quality NV centers within nanometers of such systems is challenging. Band bending caused by space charges formed at the metal-semiconductor interface force the NV center into its insensitive charge states. Here, we investigate optimizing this interface by depositing thin metal films and thin insulating layers on a series of NV ensembles at different depths to characterize the impact of metal films on different ensemble depths. We find an improvement of coherence and dephasing times we attribute to ionization of other paramagnetic defects. The insulating layer of alumina between the metal and diamond provide improved photoluminescence and higher sensitivity in all modes of sensing as compared to direct contact with the metal, providing as much as a factor of 2 increase in sensitivity, decrease of integration time by a factor of 4, for NV T 1 relaxometry measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2019

QP Statistics Spotlight: Practical versus Statistical Priorities

Randomization during data collection in a designed experiment is an effective strategy for reducing system bias and ensuring independent observations1, but at what cost should it be fully implemented? We recently encountered a scenario that highlights an important aspect of collaboration2 between statisticians, scientists and engineers – the idea of compromise for the sake of achieving wins for all team members. In a multi-million-dollar experiment with a fixed amount of time on the test equipment, each experimental run involved resetting the input values and then waiting for the continuous process to reach a new equilibrium. For example, the temperature of the furnace could be reset, but it takes some time for the test chamber to reach the new temperature and rest at that temperature for a while until all components in the chamber settle at that new setting. Similarly, a critical gas flow component also required a settling period before data could be collected that would be representative of that input setting value. In all, the experiment involved 5 factors, where 4 of the 5 were time-consuming and costly to adjust, with the duration of time needed to reach new equilibrium being dependent on how far the previous setting was from the new one for the combination of these 4 factors. For example, changing from 150° to 200° would reach equilibrium faster than changing from 100° to 200°.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2012

Improved Moderator Performance Calculations at SNS

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory reached a nominal operating power of 1 MW in September, 2009. Even at ~2/3 of its designed capacity, SNS already becomes the brightest pulsed neutron source in the world, and a premier facility for material and life science research. To provide accurate target performance estimation and to meet future development needs, we had developed an as-built model for the operating target system of SNS. Based on this asbuilt model, the moderator performance at SNS was recalculated taking advantage of the improved physics and tallying method in the Monte Carlo simulation code, MCNPX, and most recent scattering kernels. The neutron flux intensity spectra, emission time distributions of neutron pulses and moderator brightness profiles regarding the SNS moderator performance are presented and discussed. Compared to the previous results, the current calculations show ~10-20% lower in flux with improved emission time distributions of neutron pulses. The difference between the two data sets is analyzed, as well as other factors impacting the moderator performance at SNS. The current calculation results will serve as source terms for the instrument performance simulations at SNS.

Lu, Wei↗
DOE OSTI2017

Perfluorooctanoic acid affects endocytosis involving clathrin light chain A and microRNA-133b-3p in mouse testes

Perfluorooctanoic acid (PFOA) is an abundant perfluoroalkyl substance widely applied in industrial and consumer products. Among its potential health hazards, testicular toxicity is of major concern. To explore the potential effect of miRNA on post-translational regulation after PFOA exposure, changes in miRNAs were detected via miRNA array. Seventeen miRNAs were differentially expressed (eight upregulated, nine downregulated) in male mouse testes after exposure to 5 mg/kg/d of PFOA for 28 d (> 1.5-fold and P < 0.05 compared with the control). Eight of these miRNAs were further selected for TaqMan qPCR analysis. Proteomic profile analysis indicated that many changed proteins after PFOA treatment, including intersectin 1 (ITSN1), serine protease inhibitor A3K (Serpina3k), and apolipoprotein a1 (APOA1), were involved in endocytosis and blood-testis barrier (BTB) processes. These changes were further verified by immunohistochemical and Western blot analyses. Endocytosis-related genes were selected for qPCR analysis, with many found to be significantly changed after PFOA treatment, including epidermal growth factor receptor pathway substrate 8 (Eps8), Eps15, cortactin, cofilin, espin, vinculin, and zyxin. We further predicted the potential interaction between changed miRNAs and proteins, which indicated that miRNAs might play a role in the post-translational regulation of gene expression after PFOA treatment in mouse testes. Among them, miR-133b-3p/clathrin light chain A (CLTA) was selected and verified in vitro by transfection and luciferase activity assay. Results showed that PFOA exposure affects endocytosis in mouse testes and that CLTA is a potential target of miR-133b-3p. - Highlights: • Endocytosis and blood-testis barrier proteins were changed after PFOA exposure. • Seventeen miRNAs were differentially expressed in testes after PFOA exposure. • MiRNAs might play a role in gene regulation in testes after PFOA exposure.CLTA is a potential target of miR-133b-3p.

60 APPLIED LIFE SCIENCES↗