A New Method in Modeling and Simulations of Complex Oxidation Chemistry

Author(s):  
Kenneth Harstad ◽  
Josette Bellan
2012 ◽  
Vol 12 (17) ◽  
pp. 8009-8020 ◽  
Author(s):  
J. Mao ◽  
X. Ren ◽  
L. Zhang ◽  
D. M. Van Duin ◽  
R. C. Cohen ◽  
...  

Abstract. The understanding of oxidation in forest atmospheres is being challenged by measurements of unexpectedly large amounts of hydroxyl (OH). A significant number of these OH measurements were made by laser-induced fluorescence in low-pressure detection chambers (called Fluorescence Assay with Gas Expansion (FAGE)) using the Penn State Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS). We deployed a new chemical removal method to measure OH in parallel with the traditional FAGE method in a California forest. The new method gives on average only 40–60% of the OH from the traditional method and this discrepancy is temperature dependent. Evidence indicates that the new method measures atmospheric OH while the traditional method is affected by internally generated OH, possibly from oxidation of biogenic volatile organic compounds. The improved agreement between OH measured by this new technique and modeled OH suggests that oxidation chemistry in at least one forest atmosphere is better understood than previously thought.


2008 ◽  
Vol 47 (20) ◽  
pp. 3769-3772 ◽  
Author(s):  
Uriah J. Kilgore ◽  
Caitlin A. Sengelaub ◽  
Maren Pink ◽  
Alison R. Fout ◽  
Daniel J. Mindiola

2008 ◽  
Vol 120 (20) ◽  
pp. 3829-3832 ◽  
Author(s):  
Uriah J. Kilgore ◽  
Caitlin A. Sengelaub ◽  
Maren Pink ◽  
Alison R. Fout ◽  
Daniel J. Mindiola

2012 ◽  
Vol 12 (3) ◽  
pp. 6715-6744 ◽  
Author(s):  
J. Mao ◽  
X. Ren ◽  
W. H. Brune ◽  
D. M. Van Duin ◽  
R. C. Cohen ◽  
...  

Abstract. The understanding of oxidation in forest atmospheres is being challenged by measurements of unexpectedly large amounts of hydroxyl (OH). A significant number of these OH measurements were made by laser-induced fluorescence in low-pressure detection chambers (called Fluorescence Assay with Gas Expansion (FAGE)) using the Penn State Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS). We deployed a new chemical removal method to measure OH in parallel with the traditional FAGE method. The new method gives on average only 40–50% of the OH from the traditional method and this discrepancy is temperature-dependent. Evidence indicates that the new method measures atmospheric OH while the traditional method is affected by internally generated OH, possibly from oxidation of biogenic volatile organic compounds. The agreement between OH measured by this new technique and modeled OH suggests that oxidation chemistry in at least one forest atmosphere is better understood than previously thought.


Author(s):  
C. C. Clawson ◽  
L. W. Anderson ◽  
R. A. Good

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.


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