The Ozone Dynamics in the Stratosphere

2008 ◽  
Vol 59 (10) ◽  
Author(s):  
Gelu Bourceanu ◽  
Lavinia Onel ◽  
Monica Mihorianu ◽  
Militina Bourceanu
Keyword(s):  
Steady State ◽  
Coupling Reactions ◽  
Reaction Models ◽  
S Model ◽  
Catalytic Cycles ◽  
Ozone Dynamics

This work studies the O3 dynamics in the stratosphere by taking into consideration the reactions of Chapman�s model, the reactions of the O3 consuming catalytic cycles by the species HOx, ClOx and NOx and the coupling reactions between these species. The study was accomplished through two reaction models formed by 44 and 76, respectively reactions. The reactions are taken from NASA data. We found that the larger the number of the coupling reactions is, the more the ozone is protected. Indeed, at steady state the O3 concentration is higher in the case of the 76 reactions model than for the 44 reactions model.

scholarly journals Copper-Catalyzed Difluoromethylation of Alkyl Halides Enabled by Aryl Radical Activation of Carbon–Halogen Bonds

2021 ◽  
Author(s):  
Aijie Cai ◽  
Wenhao Yan ◽  
Wei Liu
Keyword(s):  
Cross Coupling ◽  
Alkyl Halides ◽  
Coupling Reactions ◽  
Diverse Range ◽  
Aryl Radicals ◽  
Cross Coupling Reactions ◽  
Alkyl Iodides ◽  
Novel Strategy ◽  
Pharmaceutical Agents ◽  
Catalytic Cycles

The engagement of unactivated alkyl halides in copper-catalyzed cross-coupling reactions has been historically challenging, due to their low reduction potential and the slow oxidative addition of copper(I) catalysts. In this work, we report a novel strategy that leverages the halogen abstraction ability of aryl radicals, thereby engaging a diverse range of alkyl iodides in copper-catalyzed Negishi–type cross-coupling reactions at room temperature. Specifically, aryl radicals generated via copper catalysis efficiently initiate the cleavage of the carbon–iodide bonds of alkyl iodides. The alkyl radicals thus generated enter the copper catalytic cycles to couple with a difluoromethyl zinc reagent, thus furnishing the alkyl difluoromethane products. This unprecedented Negishi–type difluoromethylation approach has been applied to the late-stage modification of densely functionalized pharmaceutical agents and natural products.

scholarly journals Copper-Catalyzed Difluoromethylation of Alkyl Halides Enabled by Aryl Radical Activation of Carbon–Halogen Bonds

2021 ◽  
Author(s):  
Aijie Cai ◽  
Wenhao Yan ◽  
Wei Liu
Keyword(s):  
Cross Coupling ◽  
Alkyl Halides ◽  
Coupling Reactions ◽  
Diverse Range ◽  
Aryl Radicals ◽  
Cross Coupling Reactions ◽  
Alkyl Iodides ◽  
Novel Strategy ◽  
Pharmaceutical Agents ◽  
Catalytic Cycles

The engagement of unactivated alkyl halides in copper-catalyzed cross-coupling reactions has been historically challenging, due to their low reduction potential and the slow oxidative addition of copper(I) catalysts. In this work, we report a novel strategy that leverages the halogen abstraction ability of aryl radicals, thereby engaging a diverse range of alkyl iodides in copper-catalyzed Negishi–type cross-coupling reactions at room temperature. Specifically, aryl radicals generated via copper catalysis efficiently initiate the cleavage of the carbon–iodide bonds of alkyl iodides. The alkyl radicals thus generated enter the copper catalytic cycles to couple with a difluoromethyl zinc reagent, thus furnishing the alkyl difluoromethane products. This unprecedented Negishi–type difluoromethylation approach has been applied to the late-stage modification of densely functionalized pharmaceutical agents and natural products.

Studies on Water in the Hydration Chamber of a Modified Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 544-545
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Electron Microscope ◽  
Steady State ◽  
Room Temperature ◽  
Small Mass ◽  
Equilibrium Pressure ◽  
Biological Objects ◽  
Mechanical Pump ◽  
Differential Pumping

Use of the electron microscope to examine wet objects is possible due to the small mass thickness of the equilibrium pressure of water vapor at room temperature. Previous attempts to examine hydrated biological objects and water itself used a chamber consisting of two small apertures sealed by two thin films. Extensive work in our laboratory showed that such films have an 80% failure rate when wet. Using the principle of differential pumping of the microscope column, we can use open apertures in place of thin film windows.Fig. 1 shows the modified Siemens la specimen chamber with the connections to the water supply and the auxiliary pumping station. A mechanical pump is connected to the vapor supply via a 100μ aperture to maintain steady-state conditions.

Continuous hydrogenolysis of acetal-stabilized lignin in flow

2021 ◽  
Author(s):  
Wu Lan ◽  
Yuan Peng Du ◽  
Songlan Sun ◽  
Jean Behaghel de Bueren ◽  
Florent Héroguel ◽  
...  
Keyword(s):  
Steady State ◽  
Challenges And Opportunities

We performed a steady state high-yielding depolymerization of soluble acetal-stabilized lignin in flow, which offered a window into challenges and opportunities that will be faced when continuously processing this feedstock.

Network reconstruction based on steady-state data

2008 ◽  
Vol 45 ◽  
pp. 161-176 ◽  
Author(s):  
Eduardo D. Sontag
Keyword(s):  
Steady State ◽  
Reverse Engineering ◽  
Theoretical Method ◽  
Network Reconstruction ◽  
Quasi Steady State ◽  
State Data

This paper discusses a theoretical method for the “reverse engineering” of networks based solely on steady-state (and quasi-steady-state) data.

Steady State Disinfection of Water By Ozone and sonozone

1979 ◽  
Vol 1 (4) ◽  
pp. 13-24
Author(s):  
E. Dahi ◽  
E. Lund
Keyword(s):  
Steady State
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