A detailed chemical kinetic model for oxidation of methylamine has been developed, based on theoretical work and a critical evaluation of data from the literature. The rate coefficients for the reactions of CH
The air‐sea exchange of oxygen (O2) is driven by changes in solubility, biological activity, and circulation. The total air‐sea exchange of O2has been shown to be closely related to the air‐sea exchange of heat on seasonal timescales, with the ratio of the seasonal flux of O2to heat varying with latitude, being higher in the extratropics and lower in the subtropics. This O2/heat ratio is both a fundamental biogeochemical property of air‐sea exchange and a convenient metric for testing earth system models. Current estimates of the O2/heat flux ratio rely on sparse observations of dissolved O2, leaving it fairly unconstrained. From a model ensemble we show that the ratio of the seasonal amplitude of two atmospheric tracers, atmospheric potential oxygen (APO) and the argon‐to‐nitrogen ratio (Ar/O2), exhibits a close relationship to the O2/heat ratio of the extratropics (40–
- Award ID(s):
- 1922922
- NSF-PAR ID:
- 10360303
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 126
- Issue:
- 8
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract NH + O CH NH / CH NH + HO , CH NH + H CH + NH , CH NH CH NH , and CH NH + O CH NH + HO were calculated from ab initio theory. The mechanism was validated against experimental results from batch reactors, flow reactors, shock tubes, and premixed flames. The model predicts satisfactorily explosion limits for CH NH and its oxidation in a flow reactor. However, oxidation in the presence of nitric oxide, which strongly promotes reaction at lower temperatures, is only described qualitatively. Furthermore, calculated flame speeds are higher than reported experimental values; the model does not capture the inhibiting effect of the NH group in CH NH compared to CH . More work is desirable to confirm the products of the CH NH + NO reaction and to look into possible pathways to NH in methylamine oxidation. -
Abstract We present a statistical investigation of the effects of interplanetary magnetic field (IMF) on hemispheric asymmetry in auroral currents. Nearly 6 years of magnetic field measurements from Swarm A and C satellites are analyzed. Bootstrap resampling is used to remove the difference in the number of samples and IMF conditions between the local seasons and the hemispheres. Currents are stronger in Northern Hemisphere (NH) than Southern Hemisphere (SH) for IMF B
in NH (B in SH) in most local seasons under both signs of IMF B . For B in NH (B in SH), the hemispheric difference in currents is small except in local winter when currents in NH are stronger than in SH. During B and B in NH (B and B in SH), the largest hemispheric asymmetry occurs in local winter and autumn, when the NH/SH ratio of field aligned current (FAC) is 1.18 0.09 in winter and 1.17 0.09 in autumn. During B and B in NH (B and B in SH), the largest asymmetry is observed in local autumn with NH/SH ratio of 1.16 0.07 for FAC. We also find an explicit B effect on auroral currents in a given hemisphere: on average B in NH and B in SH causes larger currents than vice versa. The explicit B effect on divergence‐free current during IMF B is in very good agreement with the B effect on the cross polar cap potential from the Super Dual Auroral Radar Network dynamic model except at SH equinox and NH summer. -
Abstract The potential for molecular hydrogen (
) generated via serpentinization to fuel subsurface microbial ecosystems independent from photosynthesis has prompted biogeochemical investigations of serpentinization‐influenced fluids. However, investigations typically sample via surface seeps or open‐borehole pumping, which can mix chemically distinct waters from different depths. Depth‐indiscriminate sampling methods could thus hinder understanding of the spatial controls on nutrient availability for microbial life. To resolve distinct groundwaters in a low‐temperature serpentinizing environment, we deployed packers (tools that seal against borehole walls during pumping) in two ‐deep, peridotite‐hosted wells in the Samail Ophiolite, Oman. Isolation and pumping of discrete intervals as deep as to below ground level revealed multiple aquifers that ranged in pH from 8 to 11. Chemical analyses and 16S rRNA gene sequencing of deep, highly reacted groundwaters bearing up to , methane ( ) and sulfate ( ) revealed an ecosystem dominated by Bacteria affiliated with the class Thermodesulfovibrionia, a group of chemolithoheterotrophs supported by oxidation coupled to reduction. In shallower, oxidized groundwaters, aerobic and denitrifying heterotrophs were relatively more abundant. High and of (up to and , respectively) indicated microbial oxidation, particularly in waters with evidence of mixing with waters. This study demonstrates the power of spatially resolving groundwaters to probe their distinct geochemical conditions and chemosynthetic communities. Such information will help improve predictions of where microbial activity in fractured rock ecosystems might occur, including beyond Earth. -
Abstract Let
be a graph, be an integer, and write for the maximum number of edges in an ‐vertex graph that is ‐partite and has no subgraph isomorphic to . The function has been studied by many researchers. Finding is a special case of the Zarankiewicz problem. We prove an analog of the Kövári‐Sós‐Turán theorem for 3‐partite graphs by showing forurn:x-wiley:10638539:media:jcd21654:jcd21654-math-0009 . Using Sidon sets constructed by Bose and Chowla, we prove that this upper bound is asymptotically best possible in the case that and is odd, that is, for . In the cases of and , we use a result of Allen, Keevash, Sudakov, and Verstraëte, to show that a similar upper bound holds for all and gives a better constant when . Finally, we point out an interesting connection between difference families from design theory and . -
Purpose We propose a method to acquire
distribution plots by encoding in instead of image space. Using this method, data is acquired in a different way from traditional spatial mapping, and allows for quick measurement of high dynamic range data. Methods To encode in
, we acquire multiple projections of a slice, each along the same direction, but using a different phase sensitivity to . Using a convex optimization formulation, we reconstruct histograms of the distribution estimates of the slice. Results We verify in vivo
distribution measurements by comparing measured distributions to distributions calculated from reference spatial maps using the Earth Mover's Distance. Phantom measurements using a surface coil show that for increased spatial variations, measured distributions using the proposed method more accurately estimate the distribution than a low‐resolution spatial map, resulting in a 37% Earth Mover's Distance decrease while using fewer measurements. Conclusion We propose and validate the performance of a method to acquire
distribution information directly without acquiring a spatial map. The method may provide faster estimates of a field for applications that do not require spatial localization, such as the transmit gain calibration of the scanner, particularly for high dynamic ranges. Magn Reson Med 77:229–236, 2017. © 2016 Wiley Periodicals, Inc.