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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 847 records · Page 47

High resolution depth profiling using near-total-reflection hard x-ray photoelectron spectroscopy

By adjusting the incidence angle of incoming x rays near the critical angle of x-ray total reflection, photoelectron intensity is strongly modulated due to the variation of x-ray penetration depth. Photoelectron spectroscopy combined with near-total reflection exhibits tunable surface sensitivity, providing depth-resolved information. In this Review, we first describe the experimental setup and specific data analysis process. We then review three different examples that show the broad application of this method. Furthermore, the emphasis is on its applications correlated to oxide heterostructures, especially quantitative depth analyses of compositions and electronic states. In the last part, we discuss the limitations of this technique, mostly in terms of the range of samples that can be studied.

36 MATERIALS SCIENCE↗

Improved quantitation of SIMS depth profile measurements of niobium via sample holder design improvements and characterization of grain orientation effects

The importance of SIMS analyses for “N-doped” impurity alloyed niobium and other surface-alloyed materials continues to increase. A major hurdle is the uncertainty of instrument calibration due to changes in sample height either from sample surface topography or from the sample holder itself. The CAMECA sample holder design allows for many types of samples to be analyzed. However, a drawback is that the holder faceplate can bend, contributing an uncertainty in the relative sensitivity factor (RSF) used to quantify the SIMS results. Here, we describe an improved sample holder having a reinforced faceplate, which prevents deflection and reduces uncertainty. Simulations show that the new design significantly reduces deflection from 10 μm to 5 nm. Sample measurements show a reduction of RSF uncertainty from this source from 4.1% to 0.95%. Grain orientation has long been suspected to affect RSF measurement as well. A bicrystal implant standard, consisting of randomly oriented and [001] grains, was successively rotated 15° between analyses. It was observed that 20% of the analyses performed on the randomly oriented grain exhibited anomalously high RSF values as well as slow sputter rates. These features were associated with the changing grain normal orientation with respect to the primary Cs + beam. The grain orientation associated with the rise in RSF was simulated and determined to be the [101] crystallographic plane, thus indicating that ion channeling was responsible for the significantly increased RSF. Focused ion beam analysis confirmed slower sputter rates for the cardinal crystallographic orientations, indicating that ion channeling occurred for each.

43 PARTICLE ACCELERATORS↗

A novel regulator of the fungal phosphate starvation response revealed by transcriptional profiling and DNA affinity purification sequencing

Cells must accurately sense and respond to nutrients to compete for resources and establish growth. Phosphate is a critical nutrient source necessary for signaling, energy metabolism, and synthesis of nucleic acids, phospholipids, and cellular metabolites. During phosphate limitation, fungi import phosphate from the environment and liberate phosphate from phosphate-containing molecules in the cell. In the model filamentous fungus Neurospora crassa, the phosphate starvation response is regulated by the conserved transcription factor NUC-1. The activity of NUC-1 is repressed by a complex of the cyclin-dependent kinase MDK-1 and the cyclin PREG when phosphate is plentiful. When phosphate is limiting, NUC-1 repression by MDK-1/PREG is relieved by the cyclin-dependent kinase inhibitor NUC-2. We investigated the global response of N. crassa to phosphate starvation. During phosphate starvation, NUC-1 directly activated the expression of genes encoding phosphatases, nucleases, and a phosphate transporter and directly repressed genes associated with the ribosome. Additionally, NUC-1 indirectly activated the expression of an uncharacterized transcription factor, which we named nuc-3. NUC-3 directly repressed the expression of genes involved in phosphate acquisition and liberation after an extended period of phosphate starvation. Additionally, NUC-3 directly repressed the expression of the cyclin-dependent kinase inhibitor nuc-2. Thus, through the combination of NUC-3 direct repression of genes in the phosphate starvation response and nuc-2, an activator of the phosphate starvation response, NUC-3 serves to act as a brake on the phosphate starvation response after an extended period of phosphate starvation. This braking mechanism could reduce transcription, a phosphate-intensive process, under conditions of extended phosphate limitation.IMPORTANCEFungi have evolved regulatory networks to respond to available nutrients. Phosphate is often a limiting nutrient for fungi that is critical for many cellular functions, including nucleic acid and phospholipid biosynthesis, cell signaling, and energy metabolism. The fungal response to phosphate limitation is important in interactions with plants and animals. We investigated the global transcriptional response to phosphate starvation and the role of a major transcriptional regulator, NUC-1, in the model filamentous fungus Neurospora crassa. Our data show that NUC-1 is a bifunctional transcription factor that directly activates phosphate acquisition genes, while directly repressing genes associated with phosphate-intensive processes. NUC-1 indirectly regulates an uncharacterized transcription factor, which we named nuc-3. NUC-3 directly represses phosphate acquisition genes and nuc-2, an activator of the phosphate starvation response, during extended periods of phosphate starvation. Thus, NUC-3 acts as a brake on the phosphate starvation response to reduce phosphate-intensive activities, like transcriptional activation, when phosphate starvation persists.

DNA affinity purification sequencing↗

End Use Load Profile (EULP) of US Building Sector resulting from mass GHP retrofits

This collection of datasets describes the change (difference) in hourly energy consumption of the U.S. residential and commercial building stock while replacing existing HVAC systems with ground source heat pumps for all the balancing areas in the US, for all buildings eligible for ground source heat pump replacement. Additional county-level data may be requested from the DOE Project Lead.

15 GEOTHERMAL ENERGY↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

SWS Building Electric Demand Profile

This dataset contains data on the electric use of the building in 15-minute increments (kilowatt-hours and average kilowatts).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗