Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Oceanography
Title: Nitrogen Fixation in Denitrified Marine Waters
Abstract: Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria), whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria). Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP), a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ). Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m−2 d−1). Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m−2 d−1) than the oxic euphotic layer (48±68 µmol m−2 d−1). Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions.
Extracted statement — Depth integrated N2 fixation rate (lower limit): 7.5
Research field: Oceanography
Title: Denitrification and nitrous oxide cycling within the upper oxycline of the eastern tropical South Pacific oxygen minimum zone
Abstract: One of the shallowest, most intense oxygen minimum zones (OMZs) is found in the eastern tropical South Pacific, off northern Chile and southern Peru. It has a strong oxygen gradient (upper oxycline) and high N2O accumulation. N2O cycling by heterotrophic denitrification along the upper oxycline was studied by measuring N2O production and consumption rates using an improved acetylene blockage method. Dissolved N2O and its isotope (15N:14N ratio in N2O or δ15N) and isotopomer composition (intramolecular distribution of 15N in the N2O or δ15Nα and δ15Nβ), dissolved O2, nutrients, and other oceanographic variables were also measured. Strong N2O accumulation (up to 86 nmol L−1) was observed in the upper oxycline followed by a decline (around 8‐12 nmol L−1) toward the OMZ core. N2O production rates by denitrification (NO2− reduction to N2O) were 2.25 to 50.0 nmol L−1 d−1, whereas N2O consumption rates (N2O reduction to N2) were 2.73 and 70.8 nmol L−1 d−1. δ15N in N2O increased from 8.57% in the middle oxycline (50‐m depth) to 14.87% toward the OMZ core (100‐m depth), indicating the progressive use of N2O as an electron acceptor by denitrifying organisms. Isotopomer signals of N2O (δ15Nα and δ15Nβ) showed an abrupt change at the middle oxycline, indicating different mechanisms of N2O production and consumption in this layer. Thus, partial denitrification along with aerobic ammonium oxidation appears to be responsible for N2O accumulation in the upper oxycline, where O2 levels fluctuate widely; N2O reduction, on the other hand, is an important pathway for N2 production. As a result, the proportion of N2O consumption relative to its production increased as O2 decreased toward the OMZ core. A N2O mass balance in the subsurface layer indicates that only a small amount of the gas could be effluxed into the atmosphere (12.7‐30.7 µmol m−2 d−1) and that most N2O is used as an electron acceptor during denitrification (107‐468 µmol m−2 d−1).
Extracted statement — N2O flux (lower limit): 12.7
Research field: Oceanography
Title: Denitrification and nitrous oxide cycling within the upper oxycline of the eastern tropical South Pacific oxygen minimum zone
Abstract: One of the shallowest, most intense oxygen minimum zones (OMZs) is found in the eastern tropical South Pacific, off northern Chile and southern Peru. It has a strong oxygen gradient (upper oxycline) and high N2O accumulation. N2O cycling by heterotrophic denitrification along the upper oxycline was studied by measuring N2O production and consumption rates using an improved acetylene blockage method. Dissolved N2O and its isotope (15N:14N ratio in N2O or δ15N) and isotopomer composition (intramolecular distribution of 15N in the N2O or δ15Nα and δ15Nβ), dissolved O2, nutrients, and other oceanographic variables were also measured. Strong N2O accumulation (up to 86 nmol L−1) was observed in the upper oxycline followed by a decline (around 8‐12 nmol L−1) toward the OMZ core. N2O production rates by denitrification (NO2− reduction to N2O) were 2.25 to 50.0 nmol L−1 d−1, whereas N2O consumption rates (N2O reduction to N2) were 2.73 and 70.8 nmol L−1 d−1. δ15N in N2O increased from 8.57% in the middle oxycline (50‐m depth) to 14.87% toward the OMZ core (100‐m depth), indicating the progressive use of N2O as an electron acceptor by denitrifying organisms. Isotopomer signals of N2O (δ15Nα and δ15Nβ) showed an abrupt change at the middle oxycline, indicating different mechanisms of N2O production and consumption in this layer. Thus, partial denitrification along with aerobic ammonium oxidation appears to be responsible for N2O accumulation in the upper oxycline, where O2 levels fluctuate widely; N2O reduction, on the other hand, is an important pathway for N2 production. As a result, the proportion of N2O consumption relative to its production increased as O2 decreased toward the OMZ core. A N2O mass balance in the subsurface layer indicates that only a small amount of the gas could be effluxed into the atmosphere (12.7‐30.7 µmol m−2 d−1) and that most N2O is used as an electron acceptor during denitrification (107‐468 µmol m−2 d−1).
Extracted statement — N2O flux (upper limit): 30.7
Research field: Oceanography
Title: Heterotrophic bacteria as major nitrogen fixers in the euphotic zone of the Indian Ocean
Abstract: Diazotrophy in the Indian Ocean is poorly understood compared to that in the Atlantic and Pacific Oceans. We first examined the basin‐scale community structure of diazotrophs and their nitrogen fixation activity within the euphotic zone during the northeast monsoon period along about 69°E from 17°N to 20°S in the oligotrophic Indian Ocean, where a shallow nitracline (49–59 m) prevailed widely and the sea surface temperature (SST) was above 25°C. Phosphate was detectable at the surface throughout the study area. The dissolved iron concentration and the ratio of iron to nitrate + nitrite at the surface were significantly higher in the Arabian Sea than in the equatorial and southern Indian Ocean. Nitrogen fixation in the Arabian Sea (24.6–47.1 μmolN m−2 d−1) was also significantly greater than that in the equatorial and southern Indian Ocean (6.27–16.6 μmolN m−2 d−1), indicating that iron could control diazotrophy in the Indian Ocean. Phylogenetic analysis of nifH showed that most diazotrophs belonged to the Proteobacteria and that cyanobacterial diazotrophs were absent in the study area except in the Arabian Sea. Furthermore, nitrogen fixation was not associated with light intensity throughout the study area. These results are consistent with nitrogen fixation in the Indian Ocean, being largely performed by heterotrophic bacteria and not by cyanobacteria. The low cyanobacterial diazotrophy was attributed to the shallow nitracline, which is rarely observed in the Pacific and Atlantic oligotrophic oceans. Because the shallower nitracline favored enhanced upward nitrate flux, the competitive advantage of cyanobacterial diazotrophs over nondiazotrophic phytoplankton was not as significant as it is in other oligotrophic oceans.
Extracted statement — Upper limit (nitrogen fixation rates): 47.1
Research field: Oceanography
Title: Rates of dinitrogen fixation and the abundance of diazotrophs in North American coastal waters between Cape Hatteras and Georges Bank
Abstract: We coupled dinitrogen (N2) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid‐Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N2 fixation were as high as 49.8 nmol N L−1 d−1 and areal rates as high as 837.9 µmol N m−2 d−1 in our study area. Our results suggest that N2 fixation occurs at high rates in coastal shelf waters that were previously thought to be unimportant sites of N2 fixation and so were excluded from calculations of pelagic marine N2 fixation. Unicellular N2‐fixing group A cyanobacteria were the most abundant diazotrophs in the Atlantic coastal waters and their abundance was comparable to, or higher than, that measured in oceanic regimes where they were discovered. High rates of N2 fixation and the high abundance of diazotrophs along the North American Mid‐Atlantic continental shelf highlight the need to revise marine N budgets to include coastal N2 fixation. Integrating areal rates of N2 fixation over the continental shelf area between Cape Hatteras and Nova Scotia, the estimated N2 fixation in this temperate shelf system is about 0.02 Tmol N yr−1, the amount previously calculated for the entire North Atlantic continental shelf. Additional studies should provide spatially, temporally, and seasonally resolved rate estimates from coastal systems to better constrain N inputs via N2 fixation from the neritic zone.
Extracted statement — Volumetric N2 fixation rate (upper limit): 49.8
Research field: Oceanography
Title: Rates of dinitrogen fixation and the abundance of diazotrophs in North American coastal waters between Cape Hatteras and Georges Bank
Abstract: We coupled dinitrogen (N2) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid‐Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N2 fixation were as high as 49.8 nmol N L−1 d−1 and areal rates as high as 837.9 µmol N m−2 d−1 in our study area. Our results suggest that N2 fixation occurs at high rates in coastal shelf waters that were previously thought to be unimportant sites of N2 fixation and so were excluded from calculations of pelagic marine N2 fixation. Unicellular N2‐fixing group A cyanobacteria were the most abundant diazotrophs in the Atlantic coastal waters and their abundance was comparable to, or higher than, that measured in oceanic regimes where they were discovered. High rates of N2 fixation and the high abundance of diazotrophs along the North American Mid‐Atlantic continental shelf highlight the need to revise marine N budgets to include coastal N2 fixation. Integrating areal rates of N2 fixation over the continental shelf area between Cape Hatteras and Nova Scotia, the estimated N2 fixation in this temperate shelf system is about 0.02 Tmol N yr−1, the amount previously calculated for the entire North Atlantic continental shelf. Additional studies should provide spatially, temporally, and seasonally resolved rate estimates from coastal systems to better constrain N inputs via N2 fixation from the neritic zone.
Extracted statement — Depth integrated N2 fixation rate (upper limit): 837.9
Research field: Planetary Sciences
Title: Raman spectroscopy as a method for mineral identification on lunar robotic exploration missions
Abstract: fiber bundle that carried the laser beam and returned the scattered radiation could be placed against surfaces at any desired angle by a deployment mechanism; otherwise, the instrument would need no moving parts. A modem micro-Raman spectrometer with its beam broadened (to .expand the spot to 50-gm diameter) and set for low resolution (7 cm ' in the 100-1400 cm ' region relative to 514.5-nm excitation), was used to simulate the spectra anticipated from a rover instrument. We present spectra for lunar mineral grains, <1 mm soil fines, breccia fragments, and glasses. From frequencies of olivine peaks, we derived sufficiently precise forsteritc contents to correlate the analyzed grains to known rock types and we obtained appropriate forsteritc contents from weak signals above background in soil fines and breccias. Peak positions of pyroxenes were sufficiently well determined to distinguish among orthorhombic, monoclinic, and triclinic (pyroxenoid) structures; additional information can be obtained from pyroxene spectra, but requires further laboratory calibration. Plagioclase provided sharp peaks in soil fines and most breccias even when the glass content was high.
Extracted statement — Excitation Frequency/Wavelength (nm): 514.5
Research field: Planetary Sciences
Title: Goldschmidt crater and the Moon's north polar region: Results from the Moon Mineralogy Mapper (M3)
Abstract: [1] Soils within the impact crater Goldschmidt have been identified as spectrally distinct from the local highland material. High spatial and spectral resolution data from the Moon Mineralogy Mapper (M3) on the Chandrayaan-1 orbiter are used to examine the character of Goldschmidt crater in detail. Spectral parameters applied to a north polar mosaic of M3 data are used to discern large-scale compositional trends at the northern high latitudes, and spectra from three widely separated regions are compared to spectra from Goldschmidt. The results highlight the compositional diversity of the lunar nearside, in particular, where feldspathic soils with a low-Ca pyroxene component are pervasive, but exclusively feldspathic regions and small areas of basaltic composition are also observed. Additionally, we find that the relative strengths of the diagnostic OH/H2O absorption feature near 3000 nm are correlated with the mineralogy of the host material. On both global and local scales, the strongest hydrous absorptions occur on the more feldspathic surfaces. Thus, M3 data suggest that while the feldspathic soils within Goldschmidt crater are enhanced in OH/H2O compared to the relatively mafic nearside polar highlands, their hydration signatures are similar to those observed in the feldspathic highlands on the farside.
Extracted statement — OH (nm): 3000
Research field: Plant Pathology
Title: Anastomosis Groups and Pathogenicity of Rhizoctonia solani and Binucleate Rhizoctonia from Potato in South Africa
Abstract: A survey of anastomosis groups (AG) of Rhizoctonia spp. associated with potato diseases was conducted in South Africa. In total, 112 Rhizoctonia solani and 19 binucleate Rhizoctonia (BNR) isolates were recovered from diseased potato plants, characterized for AG and pathogenicity. The AG identity of the isolates was confirmed using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA. R. solani isolates recovered belonged to AG 3-PT, AG 2-2IIIB, AG 4HG-I, AG 4HG-III, and AG 5, while BNR isolates belonged to AG A and AG R, with frequencies of 74, 6.1, 2.3, 2.3, 0.8, 12.2, and 2.3%, respectively. R. solani AG 3-PT was the most predominant AG and occurred in all the potato-growing regions sampled, whereas the other AG occurred in distinct locations. Different AG grouped into distinct clades, with high maximum parsimony and maximum-likelihood bootstrap support for both R. solani and BNR. An experiment under greenhouse conditions with representative isolates from different AG showed differences in aggressiveness between and within AG. Isolates of AG 2-2IIIB, AG 4HG-III, and AG R were the most aggressive in causing stem canker while AG 3-PT, AG 5, and AG R caused black scurf. This is the first comprehensive survey of R. solani and BNR on potato in South Africa using a molecular-based approach. This is the first report of R. solani AG 2-2IIIB and AG 4 HG-I causing stem and stolon canker and BNR AG A and AG R causing stem canker and black scurf on potato in South Africa.
Extracted statement — AG HG4III: 2.3
Research field: Plant Pathology
Title: Anastomosis Groups and Pathogenicity of Rhizoctonia solani and Binucleate Rhizoctonia from Potato in South Africa
Abstract: A survey of anastomosis groups (AG) of Rhizoctonia spp. associated with potato diseases was conducted in South Africa. In total, 112 Rhizoctonia solani and 19 binucleate Rhizoctonia (BNR) isolates were recovered from diseased potato plants, characterized for AG and pathogenicity. The AG identity of the isolates was confirmed using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA. R. solani isolates recovered belonged to AG 3-PT, AG 2-2IIIB, AG 4HG-I, AG 4HG-III, and AG 5, while BNR isolates belonged to AG A and AG R, with frequencies of 74, 6.1, 2.3, 2.3, 0.8, 12.2, and 2.3%, respectively. R. solani AG 3-PT was the most predominant AG and occurred in all the potato-growing regions sampled, whereas the other AG occurred in distinct locations. Different AG grouped into distinct clades, with high maximum parsimony and maximum-likelihood bootstrap support for both R. solani and BNR. An experiment under greenhouse conditions with representative isolates from different AG showed differences in aggressiveness between and within AG. Isolates of AG 2-2IIIB, AG 4HG-III, and AG R were the most aggressive in causing stem canker while AG 3-PT, AG 5, and AG R caused black scurf. This is the first comprehensive survey of R. solani and BNR on potato in South Africa using a molecular-based approach. This is the first report of R. solani AG 2-2IIIB and AG 4 HG-I causing stem and stolon canker and BNR AG A and AG R causing stem canker and black scurf on potato in South Africa.
Extracted statement — AG R: 2.3
Research field: Plant Pathology
Title: Anastomosis Groups and Pathogenicity of Rhizoctonia solani and Binucleate Rhizoctonia from Potato in South Africa
Abstract: A survey of anastomosis groups (AG) of Rhizoctonia spp. associated with potato diseases was conducted in South Africa. In total, 112 Rhizoctonia solani and 19 binucleate Rhizoctonia (BNR) isolates were recovered from diseased potato plants, characterized for AG and pathogenicity. The AG identity of the isolates was confirmed using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA. R. solani isolates recovered belonged to AG 3-PT, AG 2-2IIIB, AG 4HG-I, AG 4HG-III, and AG 5, while BNR isolates belonged to AG A and AG R, with frequencies of 74, 6.1, 2.3, 2.3, 0.8, 12.2, and 2.3%, respectively. R. solani AG 3-PT was the most predominant AG and occurred in all the potato-growing regions sampled, whereas the other AG occurred in distinct locations. Different AG grouped into distinct clades, with high maximum parsimony and maximum-likelihood bootstrap support for both R. solani and BNR. An experiment under greenhouse conditions with representative isolates from different AG showed differences in aggressiveness between and within AG. Isolates of AG 2-2IIIB, AG 4HG-III, and AG R were the most aggressive in causing stem canker while AG 3-PT, AG 5, and AG R caused black scurf. This is the first comprehensive survey of R. solani and BNR on potato in South Africa using a molecular-based approach. This is the first report of R. solani AG 2-2IIIB and AG 4 HG-I causing stem and stolon canker and BNR AG A and AG R causing stem canker and black scurf on potato in South Africa.
Extracted statement — AG 2.2IIIB: 6.1
Research field: Plant Pathology
Title: Anastomosis Groups and Pathogenicity of Rhizoctonia solani and Binucleate Rhizoctonia from Potato in South Africa
Abstract: A survey of anastomosis groups (AG) of Rhizoctonia spp. associated with potato diseases was conducted in South Africa. In total, 112 Rhizoctonia solani and 19 binucleate Rhizoctonia (BNR) isolates were recovered from diseased potato plants, characterized for AG and pathogenicity. The AG identity of the isolates was confirmed using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA. R. solani isolates recovered belonged to AG 3-PT, AG 2-2IIIB, AG 4HG-I, AG 4HG-III, and AG 5, while BNR isolates belonged to AG A and AG R, with frequencies of 74, 6.1, 2.3, 2.3, 0.8, 12.2, and 2.3%, respectively. R. solani AG 3-PT was the most predominant AG and occurred in all the potato-growing regions sampled, whereas the other AG occurred in distinct locations. Different AG grouped into distinct clades, with high maximum parsimony and maximum-likelihood bootstrap support for both R. solani and BNR. An experiment under greenhouse conditions with representative isolates from different AG showed differences in aggressiveness between and within AG. Isolates of AG 2-2IIIB, AG 4HG-III, and AG R were the most aggressive in causing stem canker while AG 3-PT, AG 5, and AG R caused black scurf. This is the first comprehensive survey of R. solani and BNR on potato in South Africa using a molecular-based approach. This is the first report of R. solani AG 2-2IIIB and AG 4 HG-I causing stem and stolon canker and BNR AG A and AG R causing stem canker and black scurf on potato in South Africa.
Extracted statement — AG A: 12.2
Research field: Plasma and Beam Physics
Title: Vacuum UV Radiation of a Plasma Jet Operated With Rare Gases at Atmospheric Pressure
Abstract: The vacuum ultraviolet (VUV) emissions from 115 to 200 nm from the effluent of an RF (1.2 MHz) capillary jet fed with pure argon and binary mixtures of argon and xenon or krypton (up to 20%) are analyzed. The feed gas mixture is emanating into air at normal pressure. The Ar2 excimer second continuum, observed in the region of 120-135 nm, prevails in the pure Ar discharge. It decreases when small amounts (as low as 0.5%) of Xe or Kr are added. In that case, the resonant emission of Xe at 147 nm (or 124 nm for Kr, respectively) becomes dominant. The Xe2 second continuum at 172 nm appears for higher admixtures of Xe (10%). Furthermore, several N I emission lines, the O I resonance line, and H I line appear due to ambient air. Two absorption bands (120.6 and 124.6 nm) are present in the spectra. Their origin could be unequivocally associated to O2 and O3. The radiance is determined end-on at varying axial distance in absolute units for various mixtures of Ar/Xe and Ar/Kr and compared to pure Ar. Integration over the entire VUV wavelength region provides the integrated spectral distribution. Maximum values of 2.2 mW middotmm-2middotsr-1 are attained in pure Ar and at a distance of 4 mm from the outlet nozzle of the discharge. By adding diminutive admixtures of Kr or Xe, the intensity and spectral distribution is effectively changed.
Extracted statement — Excitation_frequency: 1.2
Research field: Plasma and Beam Physics
Title: Etching materials with an atmospheric-pressure plasma jet
Abstract: A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of , a stable, arc-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: for Kapton ( and He only), for silicon dioxide, for tantalum and for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.
Extracted statement — Excitation_frequency: 13.56