scholarly journals Heterogeneity and Chemical Reactivity of the Remote Troposphere defined by Aircraft Measurements

2021 ◽  
Author(s):  
Hao Guo ◽  
Clare M. Flynn ◽  
Michael J. Prather ◽  
Sarah A. Strode ◽  
Stephen D. Steenrod ◽  
...  
Keyword(s):  
Data Stream ◽  
Chemical Reactivity ◽  
Probability Distributions ◽  
Organic Nitrates ◽  
Gaseous Species ◽  
Core Species ◽  
The Pacific ◽  
Remote Troposphere ◽  
Modeling Data

Abstract. The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic Oceans. ATom measured numerous gases and aerosols, particularly the gaseous species driving the chemical budgets of O3 and CH4: i.e., O3, CH4, CO, C2H6, higher alkanes, alkenes, aromatics, NOx, HNO3, HNO4, peroxyacetylnitrate, other organic nitrates, H2O, HCHO, H2O2, and CH3OOH. From the 10 s (2 km) merged observations, a modeling data stream (MDS) based on observations of the core species, consisting of 146,494 distinct air parcels has been constructed from the 4 ATom deployments, providing a continuous data stream for initializing global chemistry models and calculating the 24-hour chemical tendencies. Tendencies derived from 6 chemistry models using the ATom-1 MDS tend to agree and show a highly heterogeneous troposphere where globally 10% of the parcels control as much as 40% of the budget of O3 and CH4. Surprisingly, modeled probability distributions (100-km cells) match ATom statistics (2 km parcels), indicating that the majority of the observed heterogeneity can be resolved with current global chemistry models. On the other hand, the models' own chemical climatologies underestimate O3 production below 4 km in both Pacific and Atlantic basins because they have lower NOX levels than observed.

scholarly journals Heterogeneity and chemical reactivity of the remote troposphere defined by aircraft measurements

2021 ◽  
Vol 21 (18) ◽  
pp. 13729-13746
Author(s):  
Hao Guo ◽  
Clare M. Flynn ◽  
Michael J. Prather ◽  
Sarah A. Strode ◽  
Stephen D. Steenrod ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Chemical Species ◽  
Tropospheric Chemistry ◽  
Organic Nitrates ◽  
Data Set ◽  
Tropical Oceans ◽  
The Pacific ◽  
Probability Densities ◽  
Remote Troposphere ◽  
Modeling Data

Abstract. The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic oceans. In this paper we present and analyze a data set of 10 s (2 km) merged and gap-filled observations of the key reactive species driving the chemical budgets of O3 and CH4 (O3, CH4, CO, H2O, HCHO, H2O2, CH3OOH, C2H6, higher alkanes, alkenes, aromatics, NOx, HNO3, HNO4, peroxyacetyl nitrate, other organic nitrates), consisting of 146 494 distinct air parcels from ATom deployments 1 through 4. Six models calculated the O3 and CH4 photochemical tendencies from this modeling data stream for ATom 1. We find that 80 %–90 % of the total reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies that tropospheric chemistry is driven by a fraction of all the air. In other words, accurate simulation of the least reactive 50 % of the troposphere is unimportant for global budgets. Surprisingly, the probability densities of species and reactivities averaged on a model scale (100 km) differ only slightly from the 2 km ATom data, indicating that much of the heterogeneity in tropospheric chemistry can be captured with current global chemistry models. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find excellent agreement with the loss of O3 and CH4 but sharp disagreement with production of O3. The models sharply underestimate O3 production below 4 km in both Pacific and Atlantic basins, and this can be traced to lower NOx levels than observed. Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation.

Minimum intracellular PO2 for maximum cytochrome turnover in red muscle in situ

1987 ◽  
Vol 252 (5) ◽  
pp. H906-H915 ◽  
Author(s):  
T. E. Gayeski ◽  
R. J. Connett ◽  
C. R. Honig
Keyword(s):  
Energy Demand ◽  
Concentration Ratio ◽  
Probability Distributions ◽  
Michaelis Constant ◽  
Cytochrome Aa3 ◽  
Wide Range ◽  
Red Muscle

Probability distributions of myoglobin (Mb) saturation and intracellular PO2 were determined with subcellular spatial resolution in dog gracilis muscles during steady-state twitch contraction at 5-100% of maximal rate of O2 consumption (VO2). Calculations (Clark, A., and P. A.A. Clark. Biophys. J. 48: 931-938, 1985) and measurements (Gayeski, T. E. J., and C. R. Honig. Adv. Exp. Med. Biol. 200: 487-494, 1986) indicate that the PO2 in equilibrium with Mb is virtually identical to the PO2 at cytochrome aa3. Median intracellular PO2 and PO2 in the lower tails of probability distributions were poorly correlated with VO2. The variability of cell PO2 was greatly diminished when median PO2 was less than the PO2 for half saturation of MB, since Mb acts as a PO2 buffer. The lower tails of PO2 distributions contained almost no anoxic loci even when median PO2 was less than 1 Torr. VO2 was well correlated with the concentration ratio of phosphocreatine to free creatine (PCr/Crf) over a wide range of PO2. PO2 greater than or equal to 0.5 Torr supported maximal VO2 and energy demand. We conclude that 1) the mechanism of action of cytochrome aa3 is the same in red muscle in vivo as in mitochondria in vitro, and 2) an upper bound on the apparent Michaelis constant for maximal VO2 of red muscle is approximately 0.06 Torr.

scholarly journals Meteorological Conditions at Racetrack Playa, Death Valley National Park: Implications for Rock Production and Transport

2011 ◽  
Vol 50 (12) ◽  
pp. 2361-2375 ◽  
Author(s):  
Ralph D. Lorenz ◽  
Brian K. Jackson ◽  
Jason W. Barnes ◽  
Joseph N. Spitale ◽  
Jani Radebaugh ◽  
...  
Keyword(s):  
National Park ◽  
Probability Distributions ◽  
Meteorological Data ◽  
Time Lapse ◽  
Meteorological Conditions ◽  
Death Valley ◽  
Trail Formation ◽  
Strong Winds ◽  
Death Valley National Park

AbstractThree decades of weather records at meteorological stations near Death Valley National Park are analyzed in an attempt to gauge the frequency of conditions that might form and erase the famous trails of wind-blown rocks in the mud of Racetrack Playa. Trail formation requires the playa to be wet, followed by strong winds and/or freezing conditions. Weather records are compared with a limited set of meteorological data that were acquired in situ at the playa over three winters and that indicate freezing on 50, 29, and 15 nights during the winters of 2007/08–09/10, respectively, as well as with the hydrological condition of the playa as determined by time-lapse cameras that observed flooding over ~1, ~5, and ~40 days, respectively, during those winters. Measurements at the nearby Panamint and Hunter Mountain stations are found to be a useful, if imperfect (~50%), indicator of Racetrack Playa conditions and give some features of Racetrack Playa’s micrometeorological behavior. Wind speed probability distributions suggest that winds that are fast enough to cause unassisted rock motion are rare and therefore that freezing of water on the playa has a role in a significant fraction of movement events.

scholarly journals In Situ Alkylation of Reconstructed Human Epidermis by Methyl Methanesulfonate: A Quantitative HRMAS NMR Chemical Reactivity Mapping

2020 ◽  
Vol 33 (12) ◽  
pp. 3023-3030
Author(s):  
Hassan Srour ◽  
François-Marie Moussallieh ◽  
Karim Elbayed ◽  
Elena Giménez-Arnau ◽  
Jean-Pierre Lepoittevin
Keyword(s):  
Chemical Reactivity ◽  
Human Epidermis ◽  
Methyl Methanesulfonate ◽  
Reconstructed Human Epidermis ◽  
Hrmas Nmr

scholarly journals Characterization of Uranium Particles Produced via Pulsed Laser Deposition

2003 ◽  
Vol 802 ◽  
Author(s):  
S. C. Glade ◽  
T. W. Trelenberg ◽  
J. G. Tobin ◽  
A. V. Hamza
Keyword(s):  
Pulsed Laser Deposition ◽  
Photoelectron Spectroscopy ◽  
Pulsed Laser ◽  
Scanning Tunneling Spectroscopy ◽  
Laser Deposition ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Gaseous Species ◽  
Experimental Apparatus

ABSTRACTWe have constructed an experimental apparatus for the synthesis (via pulsed laser deposition) and analysis of nanoparticles and thin films of plutonium and other actinides. In-situ analysis techniques include x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). Also, the oxidation kinetics and the reaction kinetics of actinides with other gaseous species can be studied with this experimental apparatus. Preliminary results on depleted uranium are presented.

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