scholarly journals Quantifying the nitrogen equilibrium and photochemistry-induced isotopic effects between NO and NO<sub>2</sub>

2020 ◽  
Author(s):  
Jianghanyang Li ◽  
Xuan Zhang ◽  
Greg Michalski ◽  
John Orlando ◽  
Geoffrey Tyndall
Keyword(s):  
Significant Role ◽  
Room Temperature ◽  
Isotopic Fractionation ◽  
Enrichment Factors ◽  
Isotopic Effect ◽  
Relative Importance ◽  
Fractionation Process ◽  
Isotopic Effects ◽  
Fractionation Factors ◽  
Simulation Chamber

Abstract. The nitrogen isotopic fractionations between NO and NO2 play a significant role in determining the nitrogen isotopic compositions (δ15N) of atmospheric NO2 and nitrate. This isotopic fractionation is controlled by a combination of equilibrium isotopic effect (EIE) and Leighton Cycle induced isotopic effect (LCIE), which are poorly constrained. We quantified this isotopic fractionation process by (1) measuring the isotopic fractionation factors of EIE and LCIE in a 10 m3 atmospheric simulation chamber and (2) mathematically calculating the relative importance of EIE and LCIE. Our results showed the enrichment factors of EIE and LCIE are 1.0275 ± 0.0012, and 0.9905 ± 0.005, respectively, at room temperature. We find that EIE is the dominate factor when NOx > 20 nmol mol−1, and LCIE is more important at low NOx concentrations (

Untersuchung von Calciumisotopieeffekten bei heterogenen Austauschgleichgewichten / Investigation of Isotopic Effects of Calcium in Heterogeneous Exchange Equilibria

1972 ◽  
Vol 27 (2) ◽  
pp. 126-133 ◽  
Author(s):  
Klaus Gustav Heumann ◽  
Karl Heinrich Lieser
Keyword(s):  
Separation Factor ◽  
Calcium Concentration ◽  
Isotopic Fractionation ◽  
Ion Source ◽  
Isotopic Effect ◽  
Mass Unit ◽  
Calcium Isotopes ◽  
Heterogeneous Exchange ◽  
Loaded Column ◽  
Isotopic Effects

The following heterogeneous exchange equilibria have been examined for isotopic effects: CaCO3/Ca(aq.)2⊕. Ca-GBHA/Ca(aq.)2⊕ and Ca(Dowex 50)2⊕/Ca(aq.)2⊕ (GBHA = glyoxal-bis (2-hydroxyanil)). The isotopic ratios 44Ca/40Ca and 48Ca/40Ca were determined by means of a mass spectrometer with a thermal ion source. In the system CaCO3/Ca(aq.)2⊕, the elementary separation factor was found to be less than 1‰ or 0,5‰ per mass unit, respectively.For the exchange in the system Ca-GBHA/Ca(aq.)2⊕ in the concentration range from 0.011 to 0.84 M an elementary separation factor less than 1‰ per mass unit was found; from a three-stage experiment at a calcium concentration of 1.23 M it was concluded that the elementary isotopic effect is less than 0.4‰ per mass unit. Therefore no isotopic fractionation is to be expected for precipitation of inorganic or organic calcium salts.An enrichment of the heavier calcium isotopes in the solution was found in the case of the exchange in a Dowex 50-X12 loaded column. The isotopic effect depends on the concentration of the hydrochloric acid used as the eluent.

The young hard active Sun: soft X-ray irradiation of tryptophan in water solutions

2010 ◽  
Vol 10 (1) ◽  
pp. 67-75
Author(s):  
A. Ciaravella ◽  
D. Bongiorno ◽  
C. Cecchi-Pestellini ◽  
M.L. Testa ◽  
S. Indelicato ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Significant Role ◽  
Irradiation Dose ◽  
Room Temperature ◽  
Energy Deposition ◽  
Molecular Structures ◽  
X Rays ◽  
X Ray ◽  
Water Solutions ◽  
Isotopic Effects

AbstractThe X-ray emission of the young Sun was much harder and intense than today and might have played a significant role in the evolution of complex organics in protoplanetary environments. We investigate the effects of soft X-rays on tryptophan molecules in aqueous solutions at room temperature. As results of the irradiation experiments we detect several light species indicative of fragmentation, together with large molecular structures such as tryptophan dipeptide and tripeptide. Complexification is more evident in H2O solution than in D2O, probably due to isotopic effects. The abundances of peptides depend on the irradiation dose and decrease with increasing energy deposition. Radicals such as D, OD, H and OH, induced by the X-ray interaction with solvents, play a major role in determining the final products.

scholarly journals Significant Zr isotope variations in single zircon grains recording magma evolution history

2020 ◽  
Vol 117 (35) ◽  
pp. 21125-21131 ◽  
Author(s):  
Jing-Liang Guo ◽  
Zaicong Wang ◽  
Wen Zhang ◽  
Frédéric Moynier ◽  
Dandan Cui ◽  
...  
Keyword(s):  
Isotopic Fractionation ◽  
Major Type ◽  
Strong Temperature Dependence ◽  
Calc Alkaline ◽  
Southern Tibet ◽  
Rayleigh Distillation ◽  
Single Zircon ◽  
Magmatic History ◽  
Fractionation Factors

Zircons widely occur in magmatic rocks and often display internal zonation finely recording the magmatic history. Here, we presented in situ high-precision (2SD <0.15‰ for δ94Zr) and high–spatial-resolution (20 µm) stable Zr isotope compositions of magmatic zircons in a suite of calc-alkaline plutonic rocks from the juvenile part of the Gangdese arc, southern Tibet. These zircon grains are internally zoned with Zr isotopically light cores and increasingly heavier rims. Our data suggest the preferential incorporation of lighter Zr isotopes in zircon from the melt, which would drive the residual melt to heavier values. The Rayleigh distillation model can well explain the observed internal zoning in single zircon grains, and the best-fit models gave average zircon–melt fractionation factors for each sample ranging from 0.99955 to 0.99988. The average fractionation factors are positively correlated with the median Ti-in-zircon temperatures, indicating a strong temperature dependence of Zr isotopic fractionation. The results demonstrate that in situ Zr isotope analyses would be another powerful contribution to the geochemical toolbox related to zircon. The findings of this study solve the fundamental issue on how zircon fractionates Zr isotopes in calc-alkaline magmas, the major type of magmas that led to forming continental crust over time. The results also show the great potential of stable Zr isotopes in tracing magmatic thermal and chemical evolution and thus possibly continental crustal differentiation.

scholarly journals A Novel Framework for Selecting Informative Meteorological Stations Using Monte Carlo Feature Selection (MCFS) Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Rizwan Niaz ◽  
Ibrahim M. Almanjahie ◽  
Zulfiqar Ali ◽  
Muhammad Faisal ◽  
Ijaz Hussain
Keyword(s):  
Monte Carlo ◽  
Feature Selection ◽  
Significant Role ◽  
Meteorological Data ◽  
Accurate Estimation ◽  
Relative Importance ◽  
Drought Prediction ◽  
Monte Carlo Feature Selection ◽  
Remaining Time ◽  
Scale Data

Spatial distribution of meteorological stations has a significant role in hydrological research. The meteorological data play a significant role in drought monitoring; in this regard, accurate and suitable provision of meteorological stations is becoming crucial to improve and strengthen the skill of drought prediction. In this perspective, the choice of meteorological stations in a specific region has substantial importance for accurate estimation and continuous monitoring of drought hazards at the regional level. However, installation and data mining on a large number of meteorological stations require high cost and resources. Therefore, it is necessary to rank and find dependencies among existing meteorological stations in a particular region for further climatological analysis and reanalysis of databases. In this paper, the Monte Carlo feature selection and interdependency discovery (MCFS-ID) algorithm-based framework is proposed to identify the important meteorological station in a particular region. We applied the proposed framework on 12 meteorological stations situated in varying climatological regions of Punjab (Pakistan). We employed the drought index SPTI on 1-, 3-, 6-, 9-, 12-, 24-, and 48-month time-scale data to find the interdependencies among meteorological stations at various locations. We found that Sialkot has significance regional importance for studying SPTI-3, SPTI-6, and SPTI-48 indices. This regional importance is based on scores of relative importance (RI); for example, the RI values for SPTI-3, SPTI-6, and SPTI-48 indices are 0.1570, 0.1080, and 0.0270, respectively. Furthermore, the Jhelum station has more relative importance (RI = 0.1410 and 0.1030) for SPTI-1 and SPTI-9 indices, while varying concentration behaviour is observed in the remaining time scales.

scholarly journals Dating of Groundwater Recharge in Two Small Adjacent Aquifers in Israel and Their Initial 14C Activities

Radiocarbon ◽  
2011 ◽  
Vol 53 (1) ◽  
pp. 137-149 ◽  
Author(s):  
J Guttman ◽  
J Kronfeld ◽  
I Carmi
Keyword(s):  
Groundwater Recharge ◽  
Unsaturated Zone ◽  
Hydraulic Properties ◽  
Isotopic Fractionation ◽  
Apparent Difference ◽  
Pleistocene Aquifer ◽  
Fractionation Factors

Radiocarbon and tritium determinations were carried out in 2 adjacent small aquifers in Israel. These aquifers have small storage capacities and good hydraulic properties. Darcy calculations suggest that the aquifers contain young waters, ≃50 yr in age. 14C concentrations in the Pleistocene aquifer are between 23–60 pMC, with the lowest activity related to contamination by petroleum-based fertilizers with no 14C. 14C concentrations in the Judea Group aquifer range from 62 to 95 pMC. An apparent difference of ≃1000 yr is indicated for the average recharge age between the 2 aquifers. The tritium data suggests that the water in both aquifers is quite young. The 1000-yr difference is an artifact of initial isotopic fractionation differences through the unsaturated zone as established elsewhere for these 2 aquifers. When these individual fractionation factors (0.54 for the Pleistocene and 0.62 for the Judea Group) are used, it is revealed that both aquifers contain young water, in agreement with the Darcy calculation, which was recharged at the beginning of the period of thermonuclear atmospheric testing in the early 1960s.

Structures and isotopic fractionation factors of complexes AHA-1

1977 ◽  
Vol 99 (15) ◽  
pp. 5207-5209 ◽  
Author(s):  
Maurice M. Kreevoy ◽  
Tai-Ming Liang ◽  
Kwang-Chou Chang
Keyword(s):  
Isotopic Fractionation ◽  
Fractionation Factors

scholarly journals Amplification and Asymmetric Effects without Collateral Constraints

2017 ◽  
Vol 9 (3) ◽  
pp. 222-266 ◽  
Author(s):  
Dan Cao ◽  
Guangyu Nie
Keyword(s):  
Significant Role ◽  
Incomplete Markets ◽  
Relative Importance ◽  
Asymmetric Effects ◽  
Collateral Constraints ◽  
Exogenous Shocks ◽  
Market Incompleteness ◽  
Seminal Contribution ◽  
Vast Literature ◽  
Asymmetric Responses

The seminal contribution by Kiyotaki and Moore (1997) has spurred a vast literature on the importance of collateral constraints in propagating and amplifying shocks to the economy. However, most papers in the literature using collateral constraints assume non-state-contingent debt, i.e., markets are incomplete. To assess the relative importance of collateral constraints versus market incompleteness, we study a calibrated incomplete markets model and solve it with and without collateral constraints. We find that market incompleteness by itself plays a quantitatively significant role in the amplified and asymmetric responses of the economy, including land price and output, to exogenous shocks. (JEL D52, E32, E44, L26, O41)

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