Material Properties for Degradation and Reduction of Perfluorinated Acid in Complex Pollution System by Photo-Induced Hydrated Electrons

2014 ◽  
Vol 540 ◽  
pp. 243-246
Author(s):  
Si Bo Li ◽  
Chao Jie Zhang ◽  
Yan Qu ◽  
Qi Zhou
Keyword(s):  
Reduction Rate ◽  
Carbon Chain ◽  
Perfluorinated Acids ◽  
Rate Limiting Step ◽  
Degradation Rates ◽  
Hydrated Electrons ◽  
Perfluorinated Acid ◽  
Rate Limiting ◽  
Linear Correlations ◽  
Complex Pollution

F, the most electronegative element, is easy to catch the electrons in the bonds to form the stabilized C-F. Perfluorinated acids have high chemical stability which can tolerate acid, alkali, etc. Inhibition effect was observed in the complex pollution system in which 7 kinds of perfluorinated acids existed simultaneously. The formation of hydrated electrons was the rate-limiting step in complex pollution system, and the inhibition was increased as the carbon chain increasing. Compared the reduction rate of perfluorinated acids by photo-induced hydrated electrons in the complex pollution system with the single rate, the results showed that there were positive linear correlations between the degradation rate and photo-induced hydrated electrons. The degradation multiples of perfluorinated acids were studied, it concluded that, because of the competition among the 7 kinds of perfluorinated acids, the degradation rates were influenced.

scholarly journals Effect of Prior Oxidation on the Reduction Behavior of Magnetite-Based Iron Ore During Hydrogen-Induced Fluidized Bed Reduction

2021 ◽  
Author(s):  
Heng Zheng ◽  
Daniel Spreitzer ◽  
Thomas Wolfinger ◽  
Johannes Schenk ◽  
Runsheng Xu
Keyword(s):  
Fluidized Bed ◽  
Partial Oxidation ◽  
Iron Ore ◽  
Reduction Rate ◽  
Deep Oxidation ◽  
Initial Reaction ◽  
Oxidation Treatment ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Prior Oxidation

AbstractMagnetite-based iron ore usually shows a high sticking tendency and a poor reducibility in the fluidized bed because of its dense structure. To enhance the fluidization and reduction behaviors of magnetite-based iron ore during hydrogen-induced fluidized bed reduction, the effect of a prior oxidation treatment is investigated. The results show that the untreated magnetite-based iron ore cannot be fluidized successfully in the tested temperature range between 600 °C and 800 °C. At 600 °C reduction temperature, the de-fluidization can be avoided by a prior oxidation treatment. At higher reduction temperatures, the fluidization behavior can be further improved by an addition of 0.5 wt pct MgO. Magnesiowüstite (FexMg1−xO) is formed, which decreases the contact chance of the sticky surface between particles. Regarding to the reduction rate, a prior partial oxidation is more beneficial compared to deep oxidation. The kinetic analysis shows that MgO could promote the initial reaction. The reaction rate limiting step is no longer diffusion but chemical reaction for prior partly oxidized samples. A prior partial oxidation combined with an addition of MgO is considered to be a promising pretreatment method for a successful processing of magnetite-based iron ore.

Kinetic analysis of segmentation gene interactions in Drosophila embryos

Development ◽  
1999 ◽  
Vol 126 (7) ◽  
pp. 1515-1526 ◽  
Author(s):  
A. Nasiadka ◽  
H.M. Krause
Keyword(s):  
Target Genes ◽  
Vast Number ◽  
Rate Limiting Step ◽  
Degradation Rates ◽  
Time Required ◽  
Potential Interactions ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Synthesis And Degradation ◽  
Drosophila Embryos

A major challenge for developmental biologists in coming years will be to place the vast number of newly identified genes into precisely ordered genetic and molecular pathways. This will require efficient methods to determine which genes interact directly and indirectly. One of the most comprehensive pathways currently under study is the genetic hierarchy that controls Drosophila segmentation. Yet, many of the potential interactions within this pathway remain untested or unverified. Here, we look at one of the best-characterized components of this pathway, the homeodomain-containing transcription factor Fushi tarazu (Ftz), and analyze the response kinetics of known and putative target genes. This is achieved by providing a brief pulse of Ftz expression and measuring the time required for genes to respond. The time required for Ftz to bind and regulate its own enhancer, a well-documented interaction, is used as a standard for other direct interactions. Surprisingly, we find that both positively and negatively regulated target genes respond to Ftz with the same kinetics as autoregulation. The rate-limiting step between successive interactions (<10 minutes) is the time required for regulatory proteins to either enter or be cleared from the nucleus, indicating that protein synthesis and degradation rates are closely matched for all of the proteins studied. The matching of these two processes is likely important for the rapid and synchronous progression from one class of segmentation genes to the next. In total, 11 putative Ftz target genes are analyzed, and the data provide a substantially revised view of Ftz roles and activities within the segmentation hierarchy.

scholarly journals Maintenance of cellular levels of G-proteins: different efficiencies of αs and αo synthesis in GH3 cells

1996 ◽  
Vol 318 (3) ◽  
pp. 1071-1077 ◽  
Author(s):  
Ying LI ◽  
Ulrike MENDE ◽  
Carol LEWIS ◽  
Eva J NEER
Keyword(s):  
Protein Synthesis ◽  
G Protein ◽  
G Proteins ◽  
Gh3 Cells ◽  
Rate Limiting Step ◽  
Degradation Rates ◽  
Steady State Levels ◽  
Membrane Bound ◽  
External Signals ◽  
Rate Limiting

G-proteins couple membrane-bound receptors to intracellular effectors. Each cell has a characteristic complement of G-protein α, β and γ subunits that partly determines the cell's response to external signals. Very little is known about the mechanisms that set and maintain cellular levels of G-proteins or about potential points of regulation. We have assayed the steady-state levels of mRNA and protein for two types of G-protein subunits, αs and αo, in rat brain, heart and GH3 cells, and found that in all these cases, it takes 9- to 20-fold more mRNA to produce a given amount of αs protein than to produce the same amount of αo protein. Such a situation could arise from a relatively rapid rate of αs protein degradation, requiring rapid protein synthesis to compensate, or from relatively inefficient translation of αs mRNA compared with αo mRNA. The latter appears to be the case in GH3 cells. These cells contain 94 times more mRNA for αs than for αo, yet the rate of αs protein synthesis is only 9 times greater than αo protein synthesis. The degradation rates of the two proteins are similar (13 h for αs and 18 h for αo). To begin to define the mechanism that accounts for the fact that it takes more mRNA to synthesize a given amount of αs than αo, we asked whether there is a pool of αs mRNA that does not participate in protein synthesis. We found that virtually all αs and αo mRNA is associated with ribosomes. Therefore, all the mRNA is likely to be capable of directing protein synthesis. Since the rate-limiting step in protein synthesis is usually binding of the ribosome to mRNA at initiation, our results suggest that the relatively slow rate of αs protein synthesis is regulated by a mechanism that acts beyond initiation at peptide elongation and/or termination.

BIOSYNTHESE VON STEROIDGLUCURONIDEN BEI VERSCHIEDENEN STOFFWECHSELZUSTÄNDEN

1965 ◽  
Vol 50 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Von Herbert Schriefers ◽  
Brigitte Keck ◽  
Margot Otto
Keyword(s):  
Glycogen Content ◽  
Chemical Nature ◽  
Glucuronic Acid ◽  
Reduction Rate ◽  
Reaction Sequence ◽  
Daily Production ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Hydrolysis Of ◽  
Very High

ABSTRACT A method is described with which the synthesis of steroid glucuronides in the rat liver can be measured directly. Though, as shown in perfusion experiments with testosterone as substrate, the capacity of the liver to synthesize glucuronides is very high (9.5 μg androsterone-glucuronide equivalents/min · g corresponding to a daily production of about 100 mg), its efficiency depends on an undisturbed carbohydrate metabolism: fasting reduces the glucuronide synthesis to one fifth of the control values and alloxan-diabetes causes a decrease of thirty per cent. Intraperitoneal injection of glucose into fasting animals increases the glucuronide synthesis within two hours up to values near the normal. The decline in the rate of glucuronide production cannot be accounted for by the concomitant decrease in testosterone reduction rate. In fasting animals the lowering of the glucuronide synthesis is more pronounced than the ring A reduction rate. On the basis of these facts it is suggested that in the reaction sequence, which proceeds via the formation of dihydro- and tetrahydrocompounds to steroid glucuronides, the transfer of glucuronic acid is the rate limiting step. Obviously the fall in glucuronide synthesis is due to a decrease of liver glucose-6-phosphate and glycogen content, both of which may lead to a diminished supply of UDP-glucuronic acid. Among the aglucones liberated following enzymatic hydrolysis of the chromatographically separated glucuronide fraction, testosterone amounts to only 5 ± 2.04% of the yield expected according to the glucuronic acid estimation. Most of the aglucone fraction consists of products from testosterone hydrogenation. A report dealing with their quantitative distribution and clarifying their chemical nature is in preparation.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

2020 ◽  
Author(s):  
Chang-Sheng Wang ◽  
Sabrina Monaco ◽  
Anh Ngoc Thai ◽  
Md. Shafiqur Rahman ◽  
Chen Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Hydrogen Transfer ◽  
Acid Catalysis ◽  
Rate Limiting Step ◽  
Site Selectivity ◽  
Set Up ◽  
Site Selective ◽  
First Time ◽  
Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

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