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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Nuclear Data Sheets for A = 28

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for {sup 28}F, {sup 28}Ne, {sup 28}Na, {sup 28}Mg, {sup 28}Al, {sup 28}Si, {sup 28}P, and {sup 28}S. This evaluation for A=28 supersedes the earlier evaluations by P.M. Endt (1998En04 and 1990En08). However, additional/detailed data for these nuclides can be found in earlier evaluations 1978En02 and 1973EnVA also by P.M. Endt.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Spectroscopy and lifetime measurements near the proton drip line: P 26 , 27 , 28

We report on the observation of excited states in the neutron-deficient phosphorus isotopes 26,27,28 P via in-beam gamma-ray spectroscopy with both high-efficiency and high-resolution detector arrays. In 26 P, a previously-unobserved level has been identified at 244(3) keV, two new measurements of the astrophysically-important 3/2 + resonance in 27 P have been performed, gamma decays have been assigned to the proton-unbound levels at 2216 keV and 2483 keV in 28 P, and the gamma-ray lineshape method has been used to make the first determination of the lifetimes of the two lowest-lying excited states in 28P. The expected Thomas-Ehrman shifts were calculated and applied to levels in the mirror nuclei. The resulting level energies from this procedure were then compared with the energies of known states in 26,27,28 P.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

The {sup 30}P(p, γ){sup 31}S reaction in classical novae: progress and prospects

The unknown thermonuclear rate of the {sup 30}P(p, γ){sup 31}S reaction at classical-nova temperatures currently prohibits the accurate modeling of nova nucleosynthesis in the A ⩾ 30 region. This is hindering the calibration of nova thermometers based on observed O/S, S/Al, O/P, and P/Al abundance ratios in nova ejecta, the calibration of a meter to probe mixing at the core-envelope interface in novae based on the observed Si/H abundance ratio, and the identification of candidate pre-solar nova grains found in primitive meteorites based on laboratory measurements of their {sup 30}Si/{sup 28}Si isotopic ratios. Each of these diagnostics could address key questions in our understanding of classical novae if the {sup 30}P(p, γ){sup 31}S rate were known. We review progress on the determination of the {sup 30}P(p, γ){sup 31}S rate leading to a critical assessment of current interpretations of published data and prospects for future work.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

A single-atom quantum memory in silicon

Long coherence times and fast gate operations are desirable but often conflicting requirements for physical qubits. This conflict can be resolved by resorting to fast qubits for operations, and by storing their state in a ‘quantum memory’ while idle. The 31 P donor in silicon comes naturally equipped with a fast qubit (the electron spin) and a long-lived qubit (the 31 P nuclear spin), coexisting in a bound state at cryogenic temperatures. Here, we demonstrate storage and retrieval of quantum information from a single donor electron spin to its host phosphorus nucleus in isotopically-enriched 28 Si. The fidelity of the memory process is characterised via both state and process tomography. We report an overall process fidelity Fp ! 81%, a memory fidelity Fm ! 92%, and memory storage times up to 80 ms. These values are limited by a transient shift of the electron spin resonance frequency following highpower radiofrequency pulses.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Cation-Directed Isomerization of the U 28 Uranyl-Peroxide Cluster: Cation-Directed Isomerization of the U 28 Uranyl-Peroxide Cluster

The conformational dynamics of nanometer-sized actinide ions are exceptionally sensitive to the choice of counter-cations. A new means of following these dynamics in solution is presented that follows 1H NMR signals. The direct bond between hydrogen and phosphorus atoms in the bridging phosphonic groups of the [(UO 2 ) 28 (O 2 ) 20 (PHO 3 ) 24 (H 2 O) 12 ] 32– (U28) cluster allows unparalleled recording of the orientations of these bridges in situ. The µ 3 -PHO 3 bridges are organized into two supersets of conformers (facing inward vs. outward from the cluster), but each of these supersets additionally have four subsets that can be identified based upon orientations of the lone pairs of electrons in the associated oxygen atoms. The ensemble of these subsets changes over days or weeks depending upon bulk solution chemistry, temperature, and pressure. They also reflect cations trapped within the molecule. The 1H NMR spectra at room temperature indicate that the molecular orientation of this enormous ion tunes itself in response to solution composition, which suggests a strategy for selecting host–guest combinations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Predicting Species-Resolved Macronutrient Acquisition during Succession in a Model Phototrophic Biofilm Using an Integrated ‘Omics Approach

The principles governing acquisition and interspecies exchange of nutrients in microbial communities and how those exchanges impact community productivity are poorly understood. Here, we examine energy and macronutrient acquisition in unicyanobacterial consortia for which species-resolved genome information exists for all members, allowing us to use multi-omic approaches to predict species’ abilities to acquire resources and examine expression of resource-acquisition genes during succession. Metabolic reconstruction indicated that a majority of heterotrophic community members lacked the genes required to directly acquire the inorganic nutrients provided in culture medium, suggesting high metabolic interdependency. The sole primary producer in consortium UCC-O, cyanobacterium Phormidium sp. OSCR, displayed declining expression of energy harvest, carbon fixation, and nitrate and sulfate reduction proteins but sharply increasing phosphate transporter expression over 28 days. Most heterotrophic members likewise exhibited signs of phosphorus starvation during succession. Though similar in their responses to phosphorus limitation, heterotrophs displayed species-specific expression of nitrogen acquisition genes. These results suggest niche partitioning around nitrogen sources may structure the community when organisms directly compete for limited phosphate. Such niche complementarity around nitrogen sources may increase community diversity and productivity in phosphate-limited phototrophic communities.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

In-beam γ-ray Spectroscopy of {sup 30}P via the {sup 28}Si({sup 3}He,pγ){sup 30}P Reaction

The level structure of {sup 30}P up to 8.25 MeV was investigated via in-beam γ-ray spectroscopy using the {sup 28}Si({sup 3}He,pγ){sup 30}P reaction at 9 MeV at the University of Tsukuba Tandem Accelerator Complex in Japan. An energy level scheme was deduced from γ-γ coincidence measurements. 47 new transitions have been observed from the previously known states (mostly resonances), thereby reducing the uncertainties in the excitation energies of 17 states from 3 to 10 keV to values of < 1 keV. Furthermore, spin assignments based on measurements of γ-ray angular distributions and γ-γ directional correlation of oriented nuclei (DCO ratios) were made for several observed levels of {sup 30}P.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1976

Mineral and nitrogen balance study observations - The second manned Skylab mission

A metabolic study of important body elements, particularly those of the musculoskeletal system, was carried out on the astronauts of the Skylab 3 mission during the preflight, inflight, and postflight phases. An elevation in the level of urinary calcium similar to that observed in the 28-d Skylab flight continued throughout the flight. Significant nitrogen and phosphorus losses, apparently associated with muscle tissue loss, occurred in spite of inflight exercise programs. On the basis of these results it is predicted that capable musculoskeletal function is likely to occur in flights longer than about 9 months in duration.

Whedon, G. D.↗
DOE OSTI2018

Active Layer Soil Carbon and Nutrient Mineralization, Barrow, Alaska, 2012

This dataset consists of bulk soil characteristics as well as carbon and nutrient mineralization rates of active layer soils manually collected from the field in August, 2012, frozen, and then thawed and incubated across a range of temperatures in the laboratory for 28 day periods in 2013-2015.The soils were collected from four replicate polygons in each of the four Areas (A, B, C, and D) of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Soil samples were coincident with the established Vegetation Plots that are located in center, edge, and trough microtopography in each polygon.Data included are (1) thickness of the organic layer, (2) bulk soil characteristics including carbon, nitrogen, gravimetric water content, bulk density, and pH in 5-cm depth increments and also by soil horizon, (3) carbon, nitrogen, and phosphorus mineralization rates for soil horizons incubated aerobically (and in one case both aerobically and anaerobically) for 28 days at temperatures that included 2, 4, 8, and 12 degrees C.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Breaking the Tetra-Coordinated Framework Rule: New Clathrate Ba 8 M 24 P 28+ δ ( M =Cu/Zn)

A new clathrate type has been discovered in the Ba/Cu/Zn/P system. The crystal structure of the Ba 8 M 24 P 28+δ (M=Cu/Zn) clathrate is composed of the pentagonal dodecahedra common to clathrates along with a unique 22-vertex polyhedron with two hexagonal faces capped by additional partially occupied phosphorus sites. This is the first example of a clathrate compound where the framework atoms are not in tetrahedral or trigonal-pyramidal coordination. In Ba 8 M 24 P 28+δ a majority of the framework atoms are five- and six-coordinated, a feature more common to electron-rich intermetallics. The crystal structure of this new clathrate was determined by a combination of X-ray and neutron diffraction and was confirmed with solid-state 31P NMR spectroscopy. Based on chemical bonding analysis, the driving force for the formation of this new clathrate is the excess of electrons generated by a high concentration of Zn atoms in the framework. The rattling of guest atoms in the large cages results in a very low thermal conductivity, a unique feature of the clathrate family of compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Study of {sup 31}P(n,α){sup 28}Al reaction using d(d,n){sup 3}He for the possible interference with {sup 27}Al(n,γ){sup 28}Al - Paper 44

At McMaster we use neutrons from the {sup 7}Li(p,n){sup 7}Be reaction to measure aluminum in human subjects via the {sup 27}Al(n,γ){sup 28}Al reaction. We use proton energies of between 1.9 MeV and 2.3 MeV, yielding maximum neutron energy of 0.575 MeV. In principle, {sup 28}Al can also be produced via the {sup 31}P(n,α){sup 28}Al reaction, which has a neutron energy threshold of 2.008 MeV. When aluminum is measured in bone, there can be 10{sup 5} times the mass of phosphorus present as there is aluminum. However, this potential interference cannot arise using the {sup 7}Li(p,n){sup 7}Be reaction in the proton energy range specified. Collaborators at Atomic Energy of Canada Limited (AECL), Chalk River, Purdue University in the USA and Shanxi Medical University in Taiyuan, China are also interested in being able to measure aluminum in bone in living human subjects. Both AECL and Purdue have acquired D-D sets (accelerators producing neutrons via the d(d,n){sup 3}He reaction). These operate at high current (∼mA) and relatively low accelerating voltage (150 kV), relying on quantum mechanical tunneling through the Coulomb barrier. These D-D sets produce neutrons of energy 2.565 MeV. This is above the threshold for the {sup 31}P(n,α){sup 28}Al reaction, but we have not been able to find any report in which this reaction has had a cross section measurably greater than zero for neutron energies of less than 3 MeV. So, it is an open question as to whether the potential interfering reaction with phosphorus is a concern when using neutrons from a D-D set to measure aluminum in bone. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS2002

Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor

Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

Non-NASA Center↗
NASA NTRS1975

Mineral and nitrogen balance study - Results of metabolic observations on Skylab II 28-day orbital mission

The prediction that various stresses of flight, particularly weightlessness, would bring about significant derangements in the metabolism of the musculoskeletal system has been based on various balance-study observations of long-term immobilized or inactive bed rest. The three astronauts of Skylab II consumed a planned dietary intake of major metabolic elements in mixed foods and beverages and provided virtually complete collections of excreta for 31 days preflight, 28 days inflight, and 17 days postflight. Analyses showed that, in varying degree among the crewmen, urinary calcium increased gradually during flight in a pattern similar to that observed in bed-rest studies. Fecal calcium excretion did not change significantly, but calcium balance, owing to the urinary calcium rise, became either negative or less positive than in preflight measurement. Increased excretion and negative nitrogen and phosphorus balances inflight indicated appreciable loss of muscle tissue in all three crewmen. Significant losses also occurred inflight in potassium, sodium, and magnesium. Based on the similarity in pattern and degree between these observations of calcium, phosphorus, and nitrogen loss, musculoskeletal integrity would not be threatened in space flights of up to at least 3 months. However, if similar changes occur in the planed Skylab flights for considerably more than 28 days, concern for capable musculoskeletal function should be serious for flights of very many months' duration.

Whedon, G. D.↗
DOE OSTI2019

Peatland microbial community response to altered climate tempered by nutrient availability

Northern latitude peatlands contain large reserves of soil carbon (C) due in part to climatic constraints on decomposition, including low temperatures and water inundated soils. Under future climate change scenarios these peatlands will experience warmer temperatures, extended growing seasons, and a potential draw down of the water table, all of which improve conditions for decomposition, as well as photosynthesis. Increased photosynthesis may feedback to increase decomposition of soil C through increased root exudates to belowground decomposer communities, primarily as low molecular weight carbon compounds (LMWCC). In this study, we examine the interactive effects of climate, a combination of three temperatures and two moisture regimes, and root exudates on microbial decomposer function, measured as CO2 respiration, biomass, and potential enzyme activity. We had four substrate treatments: two common LMWCC (glycine or glucose + citric acid), chitin to simulate fungal necromass, and DI as the control. Our results support our first hypothesis that increasing temperature will increase C respiration across substrate and moisture treatments. Our second hypothesis was that compared to control and chitin, soluble substrates (i.e., LMWCC) will enhance respiration across all climate treatments. This was only partially supported. As expected, the two LMWCC substrate additions increased C respiration above the two other substrate additions at current recorded growing season average (12 °C, low treatment) and high (20 °C, med treatment) temperature treatments. Surprisingly, when the system was pushed to a higher temperature extreme (28 °C, high treatment), the low moisture controls respired more C than the other substrate × climate treatments. Potential enzyme activity and demand for phosphorus appear to explain these trends as opposed to changes to microbial biomass. Our results indicate that under projected future high temperatures, the peatland microbial community allocates additional labile C resources to enzyme production to meet nutrient demands, and as such, dampens C lost through respiration.

Keiser, Ashley D.↗
NASA NTRS2011

Retrospective Study of Serum Sclerostin Measurements in Bed Rest Subjects

Animal models and human studies suggest that osteocytes regulate the skeleton s response to mechanical unloading at the cellular level in part by an increase in sclerostin, an inhibitor of the anabolic Wnt pathway. However, few studies have reported changes in serum sclerostin in humans exposed to reduced mechanical loading. Thus, we determined changes in serum sclerostin and bone turnover markers in healthy adult men who participated in a controlled bed rest study. Seven healthy adult men (31 +/- 3 yrs old) underwent 90-day six-degree head down tilt bed rest at the University of Texas Medical Branch in Galveston's Institute for Translational Sciences - Clinical Research Center (ITS-CRC). Serum sclerostin, PTH, serum markers of bone turnover (bone specific alkaline phosphatase, RANKL/OPG, and osteocalcin), urinary calcium and phosphorus excretion, and 24 hour pooled urinary markers of bone resorption (NTX, DPD, PYD) were evaluated pre-bed rest (BL), bed rest day 28 (BR-28), bed rest day 60 (BR-60), and bed rest day 90 (BR-90). In addition, bone mineral density (BMD) was assessed by dual-energy X-ray absorptiometry (DXA) at BL, BR-60, and post bed rest day 5 (BR+5). Data are reported as mean +/- standard deviation. We used repeated measures ANOVA to compare baseline values to BR-28, BR-60, and BR-90. RESULTS Consistent with prior reports, BMD declined significantly (1-2% per month) at weight-bearing skeletal sites (spine, hip, femur neck, and calcaneus). Serum sclerostin levels were elevated above BL at BR-28 (+29% +/- 20%, p = 0.003), BR-60 (+42% +/- 31%, p < 0.001), and BR-90 (22% +/- 21%, p = 0.07). Serum PTH levels were reduced at BR-28 (-17% +/- 16%, p = 0.02), BR-60 (-24% +/- 14%, p = 0.03), and returned to baseline at BR-90 (-21% +/- 21%, p = 0.14). Serum bone turnover markers did not change, however urinary bone resorption markers and calcium were significantly elevated following bed rest (p < 0.01). CONCLUSION We observed an increase of serum sclerostin associated with decreased serum PTH and elevated bone resorption markers in otherwise healthy men subjected to long-term immobilization.

Spatz, J. M.↗
DOE OSTI2018

The composition and performance of alite-ye'elimite clinker produced at 1300 °C

Alite-ye'elimite clinker is a high cementing clinker prepared by introducing calcium sulfoaluminate, a non-silicate mineral, into the cement clinker. The mineral composition and mechanics of tricalcium silicate-rich sulfur aluminate prepared at 1300 °C are reported. The effects of copper slag and phosphorus slag on the phase composition, heat release and compressive strength were investigated. The phase composition was analysed by X-ray powder diffraction. The results show that the copper slag and phosphorus slag can lower the burn temperature of the clinker and promote the coexistence of C{sub 3}S and C{sub 4}A{sub 3} S-bar . The quality of clinker produced at 1300 °C is satisfactory. The compressive strength of mortar curing at 28 d is higher than that of P·II 52.5.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Pushing the efficiency limit of low-cost, industrially relevant Si solar cells to > 22.5% by advancing cell structures and technology innovations (Final Report)

The overall objective of this program is to achieve ~23% bifacial n-type cell efficiencies by developing and implementing optimized homogeneous or selective boron (B) emitter on front and tunnel oxide passivated contact (TOPCon) on rear side, in combination with advanced fine-line screen-printing metallization with floating busbars. During this research project, first we developed a technology roadmap to drive the 21% n-PERT cell efficiency from 21% to 23% by transforming the cell design to n-TOPCon and establishing the requirements for each layer, including B emitter, rear n-TOPCon, n-base Si and screen-printed contacts. Next, consistent with our roadmap, we developed advanced homogeneous implanted B emitter (150-180 Ω/⌫) passivated with ALD Al 2 O 3 layer capped with PECVD SiN x /SiO x double-layer antireflection coating This gave a very low recombination current density of 10-15 fA/cm 2 prior to metallization. In addition, we demonstrated metallized recombination current density of ~31 fA/cm 2 for this advanced homogeneous B emitter with industrial screen-printed, fire-through contacts with 40 μm wide grid lines, floating busbars and implementation of an advanced Ag-Al paste which resulted in local or reduced area metal-Si contact under the grid lines with virtually no emitter surface etching. This paste reduced the full area metallized J oe,metal from >1100 fA/cm 2 to ~700 fA/cm 2 . We also developed novel processes for the formation of p + /p ++ selective B emitter by a) single B diffusion with selective etch back and b) two-steps diffusion with implanted B in field region and APCVD B diffusion under the metal grid. We achieved very low un-metallized recombination current density (J 0 ) of ~18 fA/cm 2 for the selective p ++ p + emitters (30/150 Ω/⌫) and metallized J 0 of ~28 fA/cm 2 with ~3% screen-printed metal contact to p ++ regions. Next, we developed the technology for n-TOPCon by growing phosphorus-doped LPCVD and PECVD poly-Si on top of ~ 15Å chemically grown (NAO) tunnel oxide. After an optimized anneal at 875 °C for 30 min, passivated n-TOPCon have unmetallized J 0 of ~ 5 fA/cm 2 which went down further to ~ 1 fA/cm 2 after a 700 Å SiN x capping layer and simulated contact firing cycle at 770 °C. After screen-printed fire-through metallization on this n-TOPCon with ~13% metal coverage, metallized J 0 value increased to only ~5 fA/cm 2 which is among the lowest reported value to the best of our knowledge for screen-printed metallization. Finally, we integrated all the above technology innovations and enhancements and demonstrated low-cost manufacturable screen-printed n-TOPCon bifacial Si solar cell with ~23% efficiencies. Based on the experimental and theoretical understanding developed in this project, we have developed a new technology roadmap that shows that implementation of busbarless contacts, 10-20 ms bulk lifetime Si, and selective B emitter or selective TOPCon on the front can drive ~23% efficient cells achieved in this research to ~25% at low-cost.

14 SOLAR ENERGY↗