Tuning the Redox Chemistry of a Cr/SiO
            2
            Phillips Catalyst for Controlling Activity, Induction Period and Polymer Properties

The extracts from 17 ready available plants were prepared by 95% ethanol extraction in Soxhlet extractor. The crude extracts were examined for their antioxidation properties using the automatized swift test (Rancimat) and lard as a substrate. The extracts with the most promising results (Rosmarinus officinalis and Salvia officinalis) were chromatographed on silica gel column and the fractions so obtained were explored separately. Second fraction from the chromatography of rosemary extract exhibited the antioxidation activity (induction period 8 h at 0.002% wt.) comparable with the activity of butylated hydroxytoluene (BHT) at 12.5 times higher concentration (induction period 11.45 h at 0.025% wt.). The antimicrobial efficiency of these extracts was determined with the aid of three dimensional agar method on four selected microorganisms (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus). The most effective were extracts from agrimony, black tea, rosemary and sage. Extracts possessing good antioxidation activity also exhibited antimicrobial efficiency.

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Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648007 ◽

1976 ◽

Vol 36 (01) ◽

pp. 037-048 ◽

Cited By ~ 49

Author(s):

Eric P. Brass ◽

Walter B. Forman ◽

Robert V. Edwards ◽

Olgierd Lindan

Keyword(s):

Particle Size ◽

Induction Period ◽

Fibrin Clot ◽

Clot Formation ◽

Appreciable Amount ◽

Buffer System ◽

Homeostatic Mechanism ◽

Fibrin Formation ◽

Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

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Electron transfer and redox chemistry in hexa-coordinate hemoglobins

10.31274/etd-180810-4808 ◽

2016 ◽

Author(s):

Navjot Singh

Keyword(s):

Electron Transfer ◽

Redox Chemistry

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Mechanism of the propagation step in the anionic polymerization of styrene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19801047 ◽

1980 ◽

Vol 45 (4) ◽

pp. 1047-1055 ◽

Cited By ~ 2

Author(s):

Miroslav Kašpar ◽

Jiří Trekoval

Keyword(s):

Experimental Data ◽

Induction Period ◽

Anionic Polymerization ◽

Reactive Intermediate ◽

Coordination Polymerization ◽

Kinetic Dependence ◽

Mathematical Solution ◽

Slow Reaction

The paper is dealing with an investigation of the kinetic dependence of the propagation step in the anionic coordination polymerization of styrene in benzene at 303 K with "living" oligostyryllithium as initiator at the onset of the reaction. A short but distinct induction period was found, indicating a preceding slow reaction leading to the formation of a reactive intermediate, which behaves as the initiator of the reaction. Using results obtained in the first paper of this series, a new mechanism of propagation has been suggested, the mathematical solution of which is correlated with experimental data.

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The effect of electrondonors on the polymerization kinetics of isoprene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19803338 ◽

1980 ◽

Vol 45 (12) ◽

pp. 3338-3346

Author(s):

Miroslav Kašpar ◽

Jiří Trekoval

Keyword(s):

Induction Period ◽

Ethyl Ether ◽

Reaction Order ◽

Propagation Rate ◽

Reaction Scheme ◽

Polymerization Kinetics ◽

Polymerization Rate ◽

Constant Concentration ◽

Initial Concentration ◽

Kinetics Of

The effect of small additions of 1-octene, butyl ethyl ether and triethylamine on the polymerization kinetics of isoprene (2-methyl-1,3-butadiene) in benzene initiated with butyllithium was investigated by employing the GLC analysis. The addition of 1-octane was reflected only in a shorter induction period of the reaction; the effect on the propagation rate was insignificant. With the increasing amount of butyl ethyl ether, the polymerization rate increases linearly, while the reaction order with respect to the concentration of triethylamine is variable and increases from 0.33 to 0.66 with the increasing concentration of the initiator. For a constant concentration of triethylamine, the reaction order with respect to the initial concentration of the initiator was found to vary considerably, reaching even negative values. A reaction scheme was suggested, taking into account the competition between two different solvates of alkyllithium.

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Metathesis Polymerization of Phenylacetylene by Tungsten Aryloxo Complexes

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19950489 ◽

1995 ◽

Vol 60 (3) ◽

pp. 489-497 ◽

Cited By ~ 4

Author(s):

Hynek Balcar ◽

Jan Sedláček ◽

Marta Pacovská ◽

Vratislav Blechta

Keyword(s):

Molecular Weight ◽

Catalytic Activity ◽

Induction Period ◽

Average Molecular Weight ◽

Molar Fraction ◽

Molar Ratio ◽

Weight Average Molecular Weight ◽

Polymer Yield ◽

Positive Effect ◽

Ligand Addition

Catalytic activity of the tungsten aryloxo complexes WCl5(OAr) and WOCl3(OAr), where Ar = 4-t-C4H9C6H4, 2,6-(t-C4H9)2C6H3, 2,6-Cl2C6H3, 2,4,6-Cl3C6H2, and 2,4,6-Br3C6H2 in polymerization of phenylacetylene (20 °C, monomer to catalyst molar ratio = 1 000) was studied. The activity of WCl5(OAr) as unicomponent catalysts increases with increasing electron withdrawing character of the -OAr ligand. Addition of two equivalents of organotin cocatalysts (Me4Sn, Bu4Sn, Ph4Sn, Bu3SnH) to WCl5(O-C6H2Cl3-2,4 ,6) has only slight positive effect (slightly higher polymer yield and/or molecular weight of poly(phenylacetylene)s was achieved). However, in the case of WOCl3(O-C6H3Cl2-2, 6) catalyst, it enhances the activity considerably by eliminating the induction period. Poly(phenylacetylene)s prepared with the catalysts studied have weight-average molecular weight ranging from 100 000 to 200 000. They are trans-prevailing and have relatively low molar fraction of monomer units comprised in cyclohexadiene sequences (about 6%).

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Induction period of the crystallization of silver nitrate solutions in ethylene glycol

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19912142 ◽

1991 ◽

Vol 56 (10) ◽

pp. 2142-2147

Author(s):

Ivo Sláma

Keyword(s):

Ethylene Glycol ◽

Silver Nitrate ◽

Induction Period ◽

Glass Forming Ability ◽

Transformation Theory ◽

Concentration Region ◽

Glass Forming ◽

Temperature Transformation ◽

Silver Nitrate Solutions ◽

Nitrate Solutions

The dependence of the induction period of crystallization on supercooling was examined for the silver nitrate-ethylene glycol system over the concentration region of silver nitrate lome fraction of 0 to 0.12. Addition of AgNO3 to ethylene glycol was found to increase considerably the critical induction period of crystallization, although to a lesser extent than Ca(NO3)2, CaCl2, ZnCl2, LiCl and LiNO3 do. The effect of these salts on the critical induction period of crystallization in dimethylsulfoxide, dimethylformamide, dimethylacetamide and methanol was compared in terms of the solvent-rich composition limit of the glass-forming ability. By using the TTT(Time-Temperature-Transformation) theory, it has been deduced that the effect of the salts on the critical induction period of crystallization of ethylene glycol is probably due to the different dependences of viscosity on their concentration in ethylene glyco in the supercooling region.

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The supercooling ability of calcium nitrate solutions in ethylene glycol

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19892711 ◽

1989 ◽

Vol 54 (10) ◽

pp. 2711-2714

Author(s):

Ivo Sláma ◽

Jarmila Malá

Keyword(s):

Thermal Stability ◽

Ethylene Glycol ◽

Induction Period ◽

Calcium Nitrate ◽

Transformation Diagram ◽

Temperature Transformation ◽

Thermal Stability Of ◽

Nitrate Solutions

The dependence of the induction period of crystallization on the supercooling was determined for the Ca(NO3)2-ethylene glycol system at mole fractions of the former from 0 to 0.049, and treated in terms of the TTT (Time-Temperature-Transformation) diagram. Addition of Ca(NO3)2 to ethylene glycol brings about a substantial increase in the critical induction period of crystallization. The thermal stability of glasses is discussed in terms of the shape and position of the TTT curves.

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