Volcanic and Geothermal Redox Engines

Elements ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 179-184
Author(s):  
Roberto Moretti ◽  
Andri Stefánsson
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Oxidation Potential ◽  
External Factors ◽  
Geothermal Systems ◽  
Acid Base ◽  
Potential Analysis ◽  
Essential Variable ◽  
Knowing That ◽  
The Many

The redox (reduction–oxidation) potential is an essential variable that controls the chemical reactions of fluids in magmatic and associated geothermal systems. However, the evolution of the redox potential is difficult to trace from a magma’s source at depth to the surface. The key is knowing that electron transfer is the twin face of the acid–base exchanges that drive charge transfer in the many reactions that occur in multiphase and chemically complex systems. The deduced redox reactivity can reveal many features about the evolution of a system’s composition and the external factors that control it. As such, redox potential analysis is an important geochemical tool by which to monitor volcanoes and to explore geothermal systems.

scholarly journals Dithienylpyrrole Electrografting on a Surface through the Electroreduction of Diazonium Salts

Electrochem ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 20-31
Author(s):  
Thi Huong Le ◽  
Van Quyen Nguyen ◽  
Gaelle Trippe-Allard ◽  
Jean-Christophe Lacroix ◽  
Pascal Martin
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Diazonium Salts ◽  
Organic Thin Film ◽  
Organic Film ◽  
Aniline Derivative ◽  
Standard Redox Potential ◽  
Key Issues ◽  
Adhesion Process

The control of the interface and the adhesion process are key issues for the development of new application based on electrochromic materials. In this work the functionalization of an electrode’s surface through electroreduction of diazonium generated in situ from 4-(2,5-di-thiophen-2-yl-pyrrol-1-yl)-phenylamine (SNS-An) has been proposed. The synthesis of the aniline derivative SNS-An was performed and the electrografting was investigated by cyclic voltammetry on various electrodes. Then the organic thin film was fully characterized by several techniques and XPS analysis confirms the presence of an organic film based on the chemical composition of the starting monomer and allows an estimation of its thickness confirmed by AFM scratching measurements. Depending on the number of electrodeposition cycles, the thickness varies from 2 nm to 10 nm, which corresponds to a few grafted oligomers. In addition, the grafted film showed a good electrochemical stability depending on the scan rates up to 400 V/s and the electrochemical response of the modified electrode towards several redox probes showed that the attached layer acts as a conductive switch. Therefore, the electrode behaves as a barrier to electron transfer when the standard redox potential of the probe is below the layer switching potential, whereas the layer can be considered as transparent towards the electron transfer for redox probes with a redox potential above it.

scholarly journals The many versions of the painting of Tingqua’s studio: painting copying and originality in nineteenth-century canton

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Elad Yaron
Keyword(s):  
Nineteenth Century ◽  
Main Question ◽  
Art World ◽  
Old World ◽  
Job Requirements ◽  
Knowing That ◽  
The Many

Abstract Personal expression was generally not part of the job requirements of trade-painters in nineteenth-century Canton, China. They were asked to produce paintings tailored to their Western consumers’ interests, wishes, and needs. Yet, in the middle of this “art-world” lies an enigma: a set of thirteen paintings depicting the workshop of the trade-painter Tingqua, which seem, at first glance, to be duplicates of a mundane product of the industry. Closer examination, however, reveals not only that each of these versions is unique, but also that the series as a whole is actually extraordinary. The workshop paintings are full of details, including various quotes written in calligraphy, which would not have been understood either by Western or even by most Chinese viewers, but only by members of the scholar-gentry, that is, the literati of China. The main question we face before this thirteen-piece puzzle is: why did the artist plant messages or integrate codes in paintings that were sent to a world in which nobody could decode them? I propose that these workshop paintings be read as a self-portrait of a person living in a world that is witnessing a contest between two substantially different momentous cultures, each struggling to prove its superiority or dominance. Watching the demise of an old world to which he himself was contributing, Tingqua decided to treasure some of its features despite knowing that those who purchased the works would not be able to appreciate them.

Radical ions in photochemistry. 21. The photosensitized (electron transfer) tautomerization of alkenes; the phenyl alkene system

1989 ◽  
Vol 67 (4) ◽  
pp. 689-698 ◽  
Author(s):  
Donald R. Arnold ◽  
Shelley A. Mines
Keyword(s):  
Hydrogen Bond ◽  
Electron Transfer ◽  
Radical Cation ◽  
Radical Anion ◽  
Phenyl Group ◽  
Oxidation Potential ◽  
Original Position ◽  
Acetonitrile Solution ◽  
Steric Interaction ◽  
Ambident Anion

Alkenes, conjugated with a phenyl group, can be converted to nonconjugated tautomers by sensitized (electron transfer) irradiation. For example, irradiation of an acetonitrile solution of the conjugated alkene 1-phenylpropene, the electron accepting photosensitizer 1,4-dicyanobenzene, the cosensitizer biphenyl, and the base 2,4,6-trimethylpyridine gave the nonconjugated tautomer 3-phenylpropene in good yield. Similarly, 2-methyl-1-phenylpropene gave 2-methyl-3-phenylpropene, and 1-phenyl-1-butene gaveE- and Z-1-phenyl-2-butene. The reaction also works well with cyclic alkenes. For example, 1-phenylcyclohexene gave 3-phenylcyclohexene, and 1-(phenylmethylene)cyclohexane gave 1-(phenylmethyl)cyclohexene. The proposed mechanism involves the initial formation of the alkene radical cation and the sensitizer radical anion, induced by irradiation of the sensitizer and mediated by the cosensitizer. Deprotonation of the radical cation assisted by the base gives the ambident radical, which is then reduced to the anion by the sensitizer radical anion. Protonation of the ambident anion at the benzylic position completes the sequence. Reprotonation at the original position is an energy wasting step. Tautomerization is driven toward the isomer with the higher oxidation potential, which is, in the cases studied, the less thermodynamically stable isomer. The regioselectivity of the deprotonation step is dependent upon the conformation of the allylic carbon–hydrogen bond. The tautomerization of 2-methyl- 1-phenylbutene gave both 2-phenylmethyl-1-butène and 2-methyl-1-phenyl-2-butene (E and Z isomers), while 2,3-dimethyl- 1-phenylbutene gave only 3-methyl-2-phenylmethyl-1 -butene. In the latter case, steric interaction of the methyls on the isopropyl group prevents effective overlap of the tertiary carbon–hydrogen bond with the singly occupied molecular orbital, thus inhibiting deprotonation from this site. Keywords: photosensitized, electron transfer, alkene, tautomerization, radical cation.

At Ford, Turnaround Is Job One

2017 ◽  
pp. 1-15
Author(s):  
James B. Shein ◽  
Matt Bell
Keyword(s):  
Corporate Culture ◽  
Consumer Preferences ◽  
Ford Motor Company ◽  
External Factors ◽  
Company Strategy ◽  
Manufacturing Operations ◽  
The Many ◽  
The Right ◽  
Internal And External Factors ◽  
A Company

The case opens with the Ford Motor Company seemingly on the path toward bankruptcy. Ford had been bleeding red ink for more than ten years when it decided in 2006 that continuing the same turnaround attempts was not going to right the ship. The company was facing significant external challenges, such as intense competition and changing consumer preferences, as well as internal challenges, such as quality and design issues and a stifling level of corporate complexity. As the case begins, CEO Bill Ford has taken the unusual step of hiring an auto industry outsider as his replacement. Alan Mulally, a thirty-seven-year Boeing veteran and principal architect of the venerable airplane manufacturer's own massive and successful turnaround, wasted little time in getting about the business of remaking Ford. He developed a plan to: focus on the Ford brand and divest the numerous other brands the company had acquired over the years; simplify and streamline the company's manufacturing operations; and remake the corporate culture from one of fiefdoms and false optimism to collaboration and facing reality. With an ardent belief in the plan's viability, Mulally raised nearly $24 billion and began to put his plan into motion. The case explores the many causes of this once-great company's decline and the steps it took to beat the odds and get back on the path of profitability.This case demonstrates that internal issues alone can derail a company and emphasizes the importance of leadership in fostering the right corporate culture to turn a company around. Students will identify the key internal and external factors that can contribute to a company's decline and learn the importance of diagnosing issues within each of three major aspects of a company-strategy, operations, and financials-in order to develop a successful turnaround plan.

Sign in / Sign up

Export Citation Format

Share Document