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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Y(PRu)2 by Materials Project

Y(RuP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Y is bonded in a 8-coordinate geometry to eight equivalent Ru and eight equivalent P atoms. All Y–Ru bond lengths are 3.14 Å. All Y–P bond lengths are 3.11 Å. Ru is bonded in a 12-coordinate geometry to four equivalent Y and four equivalent P atoms. All Ru–P bond lengths are 2.36 Å. P is bonded in a 9-coordinate geometry to four equivalent Y, four equivalent Ru, and one P atom. The P–P bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Sn3Ru2)2 by Materials Project

YRu4Sn6 crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to four equivalent Ru and twelve Sn atoms. All Y–Ru bond lengths are 3.29 Å. There are a spread of Y–Sn bond distances ranging from 3.38–3.77 Å. Ru is bonded in a 7-coordinate geometry to one Y, two equivalent Ru, and six Sn atoms. Both Ru–Ru bond lengths are 2.84 Å. There are a spread of Ru–Sn bond distances ranging from 2.60–2.81 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 5-coordinate geometry to two equivalent Y and four equivalent Ru atoms. In the second Sn site, Sn is bonded in a 6-coordinate geometry to two equivalent Y and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Mg4Al3)4 by Materials Project

Y(Mg4Al3)4 crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five equivalent Al atoms. There are a spread of Mg–Mg bond distances ranging from 3.02–3.16 Å. There are a spread of Mg–Al bond distances ranging from 2.86–3.17 Å. In the second Mg site, Mg is bonded in a 10-coordinate geometry to three equivalent Mg, one Y, and six equivalent Al atoms. The Mg–Y bond length is 3.27 Å. All Mg–Al bond lengths are 3.16 Å. Y is bonded in a 12-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Y–Al bond lengths are 3.22 Å. Al is bonded in a 11-coordinate geometry to seven Mg, one Y, and three equivalent Al atoms. There are one shorter (2.70 Å) and two longer (2.78 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Re2Si)2 by Materials Project

Y(Re2Si)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Y is bonded in a 6-coordinate geometry to twelve equivalent Re and six equivalent Si atoms. There are four shorter (3.23 Å) and eight longer (3.35 Å) Y–Re bond lengths. There are four shorter (3.02 Å) and two longer (3.05 Å) Y–Si bond lengths. Re is bonded to three equivalent Y, six equivalent Re, and three equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing ReY3Re6Si3 cuboctahedra. There are a spread of Re–Re bond distances ranging from 2.60–2.83 Å. There are one shorter (2.45 Å) and two longer (2.56 Å) Re–Si bond lengths. Si is bonded in a 9-coordinate geometry to three equivalent Y and six equivalent Re atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(ReB)4 by Materials Project

Y(ReB)4 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to twelve equivalent Re and twelve equivalent B atoms. There are four shorter (3.08 Å) and eight longer (3.19 Å) Y–Re bond lengths. There are eight shorter (3.04 Å) and four longer (3.29 Å) Y–B bond lengths. Re is bonded in a 5-coordinate geometry to three equivalent Y and five equivalent B atoms. There are three shorter (2.22 Å) and two longer (2.34 Å) Re–B bond lengths. B is bonded in a 6-coordinate geometry to three equivalent Y, five equivalent Re, and one B atom. The B–B bond length is 1.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Ga5Mo)8 by Materials Project

Y(MoGa5)8 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Y is bonded in a 8-coordinate geometry to two equivalent Mo and six equivalent Ga atoms. Both Y–Mo bond lengths are 3.15 Å. All Y–Ga bond lengths are 2.97 Å. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded in a 10-coordinate geometry to one Y and nine Ga atoms. There are a spread of Mo–Ga bond distances ranging from 2.62–2.66 Å. In the second Mo site, Mo is bonded in a 10-coordinate geometry to ten Ga atoms. There are a spread of Mo–Ga bond distances ranging from 2.54–2.70 Å. There are eight inequivalent Ga sites. In the first Ga site, Ga is bonded in a cuboctahedral geometry to twelve Ga atoms. There are six shorter (2.92 Å) and six longer (3.04 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a distorted linear geometry to two equivalent Mo atoms. In the third Ga site, Ga is bonded in a 2-coordinate geometry to two equivalent Mo and two equivalent Ga atoms. There are one shorter (2.74 Å) and one longer (2.91 Å) Ga–Ga bond lengths. In the fourth Ga site, Ga is bonded in a distorted bent 150 degrees geometry to two equivalent Mo and one Ga atom. In the fifth Ga site, Ga is bonded in a distorted bent 150 degrees geometry to two Mo and one Ga atom. In the sixth Ga site, Ga is bonded in a 2-coordinate geometry to two equivalent Mo and one Ga atom. The Ga–Ga bond length is 2.73 Å. In the seventh Ga site, Ga is bonded in a 2-coordinate geometry to two Mo and two equivalent Ga atoms. There are one shorter (2.76 Å) and one longer (3.00 Å) Ga–Ga bond lengths. In the eighth Ga site, Ga is bonded in a 8-coordinate geometry to one Y, two Mo, and five Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(BO2)6 by Materials Project

Y(BO2)6 crystallizes in the trigonal R3c space group. The structure is three-dimensional. Y is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Y–O bond distances ranging from 2.36–2.49 Å. There are two inequivalent B sites. In the first B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.36–1.39 Å. In the second B site, B is bonded in a tetrahedral geometry to four O atoms. There are a spread of B–O bond distances ranging from 1.45–1.51 Å. There are four inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to one Y and two B atoms. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Y and one B atom. In the third O site, O is bonded in a distorted bent 120 degrees geometry to one Y and two B atoms. In the fourth O site, O is bonded in a bent 120 degrees geometry to two B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Fe2Ge)2 by Materials Project

YFe4Ge2 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Y is bonded in a 6-coordinate geometry to twelve Fe and six equivalent Ge atoms. There are a spread of Y–Fe bond distances ranging from 3.05–3.40 Å. There are two shorter (2.95 Å) and four longer (2.97 Å) Y–Ge bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a 1-coordinate geometry to three equivalent Y, four Fe, and four equivalent Ge atoms. There are a spread of Fe–Fe bond distances ranging from 2.46–2.64 Å. There are a spread of Fe–Ge bond distances ranging from 2.48–2.68 Å. In the second Fe site, Fe is bonded in a 3-coordinate geometry to three equivalent Y, three equivalent Fe, and three equivalent Ge atoms. There are two shorter (2.41 Å) and one longer (2.42 Å) Fe–Ge bond lengths. Ge is bonded in a 10-coordinate geometry to three equivalent Y and seven Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Observation of the Y(4230) and a new structure in ${\boldsymbol e^+\boldsymbol e^- \boldsymbol\rightarrow \boldsymbol K^+\boldsymbol K^-\boldsymbol J/\boldsymbol\psi}$

The cross sections of $e^+e^- \rightarrow K^+K^-J/\psi$ at center-of-mass energies from 4.127 to 4.600 GeV are measured based on 15.6 fb -1 data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in the line shape of the cross sections. The mass and width of the first structure are measured to be ($4225.3\pm2.3\pm21.5$) MeV and ($72.9\pm6.1\pm30.8$) MeV, respectively. They are consistent with those of the established $Y(4230)$. The second structure is observed for the first time with a statistical significance greater than 8σ, denoted as $Y(4500)$. Its mass and width are determined to be ($4484.7\pm13.3\pm24.1$) MeV and ($111.1\pm30.1\pm15.2$) MeV, respectively. The first presented uncertainties are statistical and the second ones are systematic. The product of the electronic partial width with the decay branching fraction $\Gamma(Y(4230)\to e^+ e^-) \mathcal{B}(Y(4230) \to K^+ K^- J/\psi)$ is reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Performance of a triple-GEM detector with capacitive-sharing 3-coordinate (X–Y–U)-strip anode readout

The concept of capacitive-sharing readout, described in detail in a previous study, offers the possibility for the development of high-performance three-coordinates (X--Y--U)-strip readout for Micro Pattern Gaseous Detectors (MPGDs) using simple standard PCB fabrication techniques. Capacitive-sharing (X--Y--U)-strip readout allows simultaneous measurement of the Cartesian coordinates x and y of the position of the particles together with a third coordinate u along the diagonal axis in a single readout PCB. This provides a powerful tool to address multiple-hit ambiguity and enable pattern recognition capabilities in moderate particle flux environment of collider or fixed target experiments in high energy physics HEP) and nuclear physics (NP). We present in this paper the performance of a 10 cm × 10 cm triple-GEM detector with capacitive-sharing (X--Y--U)-strip anode readout. Spatial resolutions of the order of $\sigma_{x}^{res}$ = 71.6 $\pm$ 0.8 $\mu$m for X-strips, $\sigma_{y}^{res}$ = 56.2 $\pm$ 0.9 $\mu$m for Y-strips and $\sigma_{u}^{res}$ = 75.2 $\pm$ 0.9 $\mu$m for U-strips have been obtained at a beam test at Thomas Jefferson National Accelerator Facility (Jefferson Lab). Modifications of the readout design of future prototypes to improve the spatial resolution and challenges in scaling to large-area MPGDs are discussed.

(X-Y-U) strip↗
NASA NTRS2013

K-Ca Dating of Alkali-Rich Fragments in the Y-74442 and Bhola LL-Chondritic Breccias

Alkali-rich igneous fragments in the brecciated LL-chondrites, Krahenberg (LL5) [1], Bhola (LL3-6) [2], Siena (LL5) [3] and Yamato (Y)-74442 (LL4) [4-6], show characteristic fractionation patterns of alkali and alkaline elements [7]. The alkali-rich fragments in Krahenberg, Bhola and Y-74442 are very similar in mineralogy and petrography, suggesting that they could have come from related precursor materials [6]. Recently we reported Rb-Sr isotopic systematics of alkali-rich igneous rock fragments in Y-74442: nine fragments from Y-74442 yield the Rb-Sr age of 4429 plus or minus 54 Ma (2 sigma) for lambda(Rb-87) = 0.01402 Ga(exp -1) [8] with the initial ratio of Sr-87/Sr-86 = 0.7144 plus or minus 0.0094 (2 sigma) [9]. The Rb-Sr age of the alkali-rich fragments of Y-74442 is younger than the primary Rb-Sr age of 4541 plus or minus 14 Ma for LL-chondrite whole-rock samples [10], implying that they formed after accumulation of LL-chondrite parental bodies, although enrichment may have happened earlier. Marshall and DePaolo [11,12] demonstrated that the K-40 - Ca-40 decay system could be an important chronometer as well as a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [13,14] and more recently Simon et al. [15] determined K-Ca ages of lunar granitic rocks, and showed the application of the K-Ca chronometer for K-rich planetary materials. Since alkali-rich fragments in the LL-chondritic breccias are highly enriched in K, we can expect enhancements of radiogenic Ca-40. Here, we report preliminary results of K-Ca isotopic systematics of alkali-rich fragments in the LL-chondritic breccias, Y-74442 and Bhola.

Yokoyama, T↗
DOE OSTI2022

Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn): High Chemical Flexibility Resulting in Good Nonlinear-Optical Properties

Seven acentric sulfides Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) were grown by a high-temperature salt flux method. The crystal structures of the Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) compounds were determined by single-crystal X-ray diffraction with the aid of solid-state NMR spectroscopy. The Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi) compounds are isostructural and crystallize in the Ba 6 Ag 4 Sn 4 S 16 structure type. The Sn-containing compound exhibits high structural similarity to Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi) with the presence of an interstitial atomic position partially occupied by Sn atoms. The chemical bonding characteristics of Ba 6 (Cu 2.9 Sn 0.4 )Sn 4 S 16 were understood with electron localization function calculations coupled with crystal orbital Hamilton population calculations. The Ba–S and Cu–S interactions are dominantly ionic, but the Sn–S interactions consist of strong covalent bonding characteristics in Ba 6 (Cu 2.9 Sn 0.4 )Sn 4 S 16 . The monovalent Cu atoms, mixed with certain metals with various oxidation states, significantly shift the optical properties of the Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi) compounds. This results in a good balance between the second-harmonic-generation (SHG) response and laser damage threshold (LDT). Ba 6 (Cu 1.9 Zn 1.1 )Sn 4 S 16 possesses a high SHG response and a high LDT of 2.8 × AGS and 3 × AGS, respectively. Here, a density functional theory calculation revealed that CuS 4 and SnS 4 tetrahedra significantly contribute to the SHG response in Ba 6 (Cu 2 Mg)Sn 4 S 16 , which also confirmed that CuS 4 tetrahedra are crucial for the stability and optical properties of the Ba 6 (Cu x Z y )Sn 4 S 16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) compounds revealed by electronic structure analysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Operando Characterization of Fe in Doped Ni x (Fe 1– x )O y H z Catalysts for Electrochemical Oxygen Evolution

Iron-doped nickel oxyhydroxides, Ni x (Fe 1– x )O y H z , are among the most promising oxygen evolution reaction (OER) electrocatalysts in alkaline environments. Although iron (Fe) significantly enhances the catalytic activity, there is still no clear consensus on whether Fe directly participates in the reaction or merely acts as a promoter. To elucidate the Fe’s role, we performed operando X-ray spectroscopy studies supported by DFT on Ni x (Fe 1– x )O y H z electrocatalysts. We probed the reversible changes in the structure and electronic character of Ni x (Fe 1– x )O y H z as the electrode potential is cycled between the resting (here at 1.10 V RHE ) and operational states (1.66 V RHE ). DFT calculations and XAS simulations on a library of Fe structures in various NiO y H z environments are in favor of a distorted local octahedral Fe(III)O 3 (OH) 3 configuration at the resting state with the NiO y H z scaffold going from α-Ni(OH) 2 to γ-NiOOH as the potential is increased. Under catalytic conditions, EXAFS and HERFD spectra reveal changes in p-d mixing (covalency) relative to the resting state between O/OH ligands and Fe leading to a shift from octahedral to square pyramidal coordination at the Fe site. XES measurements and theoretical simulations further support that the Fe equilibrium structure remains in a formal Fe(III) state under both resting and operational conditions. These spectral changes are attributed to potential dependent structural rearrangements around Fe. The results suggest that ligand dissociation leads to the C 4v symmetry as the most stable intermediate of the Fe during OER. This implies that Fe has a weakly coordinated or easily dissociable ligand that could serve to coordinate the O–O bond formation and, tentatively, play an active role in the Ni x (Fe 1– x )O y H z electrocatalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Bonding similarities and differences between Y–Sb–Te and Sc–Sb–Te phase-change memory materials

The scandium (Sc) – alloyed Sb 2 Te 3 phase-change alloy has recently been found to enable ultrafast crystal nucleation due to the formation of Sc-stabilized octahedral motifs in the amorphous phase, rendering cache-type phase-change memory feasible. When yttrium (Y) is added, however, non-octahedral bonding patterns form in the amorphous Sb 2 Te 3 -based network even though Y has a valence electron configuration similar to that of Sc and also forms perfect octahedral bonding environments with tellurium in the YTe crystal. Here we elucidate the origin of this difference between Sc and Y, by carrying out thorough ab initio simulations and orbital-based bonding analyses on amorphous Y–Sb–Te and Sc–Sb–Te compounds. We also demonstrate how the smooth overlap of atomic positions (SOAP) similarity kernel can be used to quantify the structural similarity of local motifs in the amorphous phase with respect to various crystalline yttrium and scandium tellurides, both in the nearest-neighbor shell and beyond. We discover that the bonding contrast of Y- and Sc-centered structural motifs in amorphous Sb 2 Te 3 stems from their parent crystals at high Te concentrations. The larger atomic radius of Y and the weaker charge transfer when bonded with Te is found to allow more Te neighbors and cause a more open bonding environment, leading to higher coordination numbers and non-octahedral environments. We discuss the implications of the different local environments for practical applications in memory devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Phase diagrams and polarization reversal in nanosized Hf x Zr 1–x O 2–y

To describe the polar properties of nanosized Hf x Zr 1–x O 2–y , we evolve the “effective” Landau–Ginzburg–Devonshire (LGD) model based on the parametrization of the Landau expansion coefficients for polar and antipolar orderings. We have shown that the effective LGD model can predict the influence of screening conditions and size effects on phase diagrams, polarization reversal, and structural properties of nanosized Hf x Zr 1–x O 2–y of various shapes and sizes. To verify the model, we use the available experimental results for Hf x Zr 1–x O 2 thin films and oxygen-deficient HfO2–y nanoparticles prepared under different annealing conditions. X-ray diffraction, which was used to determine the phase composition of the HfO 2–y nanoparticles, revealed the formation of a ferroelectric orthorhombic phase in them. Micro-Raman spectroscopy was used to explore the correlation of lattice dynamics and structural changes that depend on the oxygen vacancy concentration in the HfO 2–y nanoparticles. Since our approach allows us to determine the conditions (shape, sizes, Zr content, and/or oxygen vacancy amount) for which nanosized Hf x Zr 1–x O 2–y are ferroelectric or antiferroelectric, we hope that the obtained results are useful for creation of next generation Si-compatible ferroelectric gate oxide nanomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Y-12 Groundwater Protection Program Groundwater and Surface Water Sampling and Analysis Plan (CY 2021)

This plan provides a description of the groundwater and surface water quality monitoring activities planned for calendar year (CY) 2021 at the U.S. Department of Energy Y-12 National Security Complex (Y-12) that will be managed by the Y-12 Groundwater Protection Program (GWPP). Groundwater and surface water monitoring is performed by the GWPP. Groundwater and surface water monitoring will be performed in three hydrogeologic regimes at Y-12: the Bear Creek Hydrogeologic Regime (Bear Creek Regime), the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime), and the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime). The Bear Creek and East Fork regimes are located in Bear Creek Valley and the Chestnut Ridge Regime is located south of Y-12. Additional surface water monitoring will be performed north of Pine Ridge along the boundary of the Oak Ridge Reservation. The following sections of this report provide details regarding the CY 2021 groundwater and surface water monitoring activities. Section 2 describes the monitoring locations in each regime and the processes used to select the sampling locations. A description of the field measurements and laboratory analytes is provided in Section 3. Sample collection methods and procedures are described in Section 4, and Section 5 lists the documents cited for more detailed operational and technical information. The narrative sections of the report reference several appendices. Figures (maps and diagrams) and tables (excluding a data summary table presented in Section 4) are in Appendix A and Appendix B, respectively. Groundwater Monitoring Schedules (when issued throughout CY 2021) will be inserted in Appendix C, and addenda to this plan (if issued) will be inserted in Appendix D. Laboratory requirements (bottle lists, holding times, etc.) are provided in Appendix E, and an approved Waste Management Plan is provided in Appendix F. Modifications to the CY 2021 monitoring program may be necessary during implementation. Changes in programmatic requirements may alter the analytes specified for selected monitoring wells or may add or remove wells from the planned monitoring network. Each modification to the monitoring program will be approved by the Y-12 GWPP manager and documented as an addendum to this sampling and analysis plan.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1993

Stratospheric NO(y) measurements on the NASA DC-8 during AASE 2

We survey measurements of stratospheric NO(y) on the NASA DC-8 during AASE 2 in early 1992. Emphasis is on correlations with other long-lived species: O3, N2O, and CH4. No cases of extremely high NO(y)/O3 ratios were seen in 1992. This suggests that denitrification at higher altitudes was less pervasive than in 1989. Values of NO(y)/O3 in 1992 are comparable to, though perhaps lower than, those measured in 1989. The correlation of NO(y) with N2O changes over the course of the mission. Relative to the correlation for the whole season, low values of NO(y) occur in February, most notably on the 22nd. The reason for the low NO(y) is unknown. It is generally too warm at DC-8 altitudes for the presence of Polar Stratospheric Cloud (PSC) particles, but denitrification at higher altitudes, followed by descent, might account for the low values seen on 22 February. However, this may be unlikely since the NASA ER-2, flying during the same period, saw no evidence of denitrification at higher altitudes (Loewenstein et al., 1993).

Weinheimer, A. J.↗
NASA NTRS1993

Stratospheric NO(y) Measurements on the NASA DC-8 during AASE 2

We survey measurements of stratospheric NO(y) on the NASA DC-8 during AASE 2 in early 1992. Emphasis is on correlations with other long-lived species: O3, N2O, and CH4. No cases of extremely high NO(y)/O3 ratios were seen in 1992. This suggests that denitrification at higher altitudes was less pervasive than in 1989. Values of NO(y)/O3 in 1992 are comparable to, though perhaps lower than, those measured in 1989. The correlation of NO(y) with N2O changes over the course of the mission. Relative to the correlation for the whole season, low values of NO(y) occur in February, most notably on the 22nd. The reason for the low NO(y) is unknown It is generally too warm at DC-8 altitudes for the presence of PSC particles, but denitrification at higher altitudes, followed by descent, might account for the low values seen on 22 February. However, this may be unlikely since the NASA ER-2, flying during the same period, saw no evidence of denitrification at higher altitudes.

Weinheimer, A. J.↗