Statistical Theories for Unimolecular Rate Constant Calculation in Isolated Systems

1992 ◽  
pp. 170-211
Author(s):  
Eugen Illenberger ◽  
Jacques Momigny
Keyword(s):  
Rate Constant ◽  
Isolated Systems

Functional Properties of p-Anisoylated Plasmin-Staphylokinase Complex

1993 ◽  
Vol 70 (02) ◽  
pp. 326-331 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
R A G Smith ◽  
D Collen
Keyword(s):  
Human Plasma ◽  
Rate Constant ◽  
Time Course ◽  
Bolus Injection ◽  
Similar Rate ◽  
Clot Lysis ◽  
Lag Phase ◽  
Plasma Clot ◽  
Rapid Clearance ◽  
Stoichiometric Complex

SummaryThe kinetic and fibrinolytic properties of a reversibly acylated stoichiometric complex between human plasmin and recombinant staphylokinase (plasmin-STAR complex) were evaluated. The acylation rate constant of plasmin-STAR by p-amidinophenyl-p’-anisate-HCI was 52 M-1 s-1 and its deacylation rate constant 1.2 × 10-4 s-1 (t½ of 95 min) which are respectively 50-fold and around 3-fold lower than for the plasmin-streptokinase complex. The acylated complex was stable as evidenced by binding to lysine-Sepharose. However, following an initial short lag phase, the acylated plasmin-STAR complex activated plasminogen at a similar rate as the unblocked complex, whereas the acylated plasmin-streptokinase complex did not activate plasminogen. These findings indicate that STAR, unlike streptokinase, dissociates from its acylated complex with plasmin in the presence of excess plasminogen. In agreement with this hypothesis, the time course of the lysis of a 125I-fibrin labeled plasma clot submerged in citrated human plasma, is similar for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR (50% clot lysis in 2 h requires 12 nM of each agent). The plasma clearances of STAR-related antigen following bolus injection in hamsters were 1.0 to 1.5 ml/min for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR, as a result of short initial half-lives of 2.0 to 2.5 min.The dissociation of the anisoylated plasmin-STAR complex and its consequent rapid clearance suggest that it has no apparent advantages as compared to free STAR for clinical thrombolysis.

Morphological and Photodecomposition Rate Constant Study of PVC Films Doped with Sulfadiazine Tin(IV) Complexes

2020 ◽  
Vol 14 (2) ◽  
pp. 88
Author(s):  
Emad Yousif
Keyword(s):  
Radiation Exposure ◽  
Uv Radiation ◽  
Rate Constant ◽  
Experimental Results

This article focus on the calculation of photodecomposition rate constant of PVC films that containing sulfadiazine tin(IV) complexes 1-3 as photostabilzers during UV radiation exposure. This constant calculated as a method for evaluating the efficiency of sulfadiazine tin(IV) complexes 1-3 when used as a PVC photostabilizers after 300 hours of irradiation. The experimental results showed that sulfadiazine tin(IV) complexes 1-3 have reduced the rate of photodecomposition constant value of PVC films significantly with comparison to PVC (blank).

Dynamic Emergence of Nanostructure and Transport Properties in Perfluorinated Sulfonic Acid Ionomers

2020 ◽  
Author(s):  
Adlai Katzenberg ◽  
Debdyuti Mukherjee ◽  
Peter J. Dudenas ◽  
Yoshiyuki Okamoto ◽  
Ahmet Kusoglu ◽  
...  
Keyword(s):  
Rate Constant ◽  
Sulfonic Acid ◽  
Mass Fraction ◽  
Gas Permeability ◽  
Transport Processes ◽  
Segmental Mobility ◽  
The Matrix ◽  
Swelling Rate ◽  
Ion Conducting ◽  
Perfluorinated Sulfonic Acid

<p>Limitations in fuel cell electrode performance have motivated the development of ion-conducting binders (ionomers) with high gas permeability. Such ionomers have been achieved by copolymerization of perfluorinated sulfonic acid (PFSA) monomers with bulky and asymmetric monomers, leading to a glassy ionomer matrix with chemical and mechanical properties that differ substantially from common PFSA ionomers (e.g., Nafion™). In this study, we use perfluorodioxolane-based ionomers to provide fundamental insights into the role of the matrix chemical structure on the dynamics of structural and transport processes in ion-conducting polymers. Through <i>in-situ</i> water uptake measurements, we demonstrate that ionomer water sorption kinetics depend strongly on the properties and mass fraction of the matrix. As the PFSA mass fraction was increased from 0.26 to 0.57, the Fickian swelling rate constant decreased from 0.8 s<sup>-1</sup> to 0.2 s<sup>-1</sup>, while the relaxation rate constant increased from 3.1×10<sup>-3</sup> s<sup>-1</sup> to 4.0×10<sup>-3</sup>. The true swelling rate, in nm s<sup>-1</sup>, was determined by the chemical nature of the matrix; all dioxolane-containing materials exhibited swelling rates ~1.5 - 2 nm s<sup>-1</sup> compared to ~3 nm s<sup>-1</sup> for Nafion. Likewise, Nafion underwent relaxation at twice the rate of the fastest-relaxing dioxolane ionomer. Reduced swelling and relaxation kinetics are due to limited matrix segmental mobility of the dioxolane-containing ionomers. We demonstrate that changes in conductivity are strongly tied to the polymer relaxation, revealing the decoupled roles of initial swelling and relaxation on hydration, nanostructure, and ion transport in perfluorinated ionomers. </p>

Development of Sustained Release Multi-Component Microparticulate System of Diclofenac Sodium and Tizanidine Hydrochloride

1970 ◽  
Vol 1 (1) ◽  
pp. 97-105
Author(s):  
Kamlesh Dashora ◽  
Shailendra Saraf ◽  
Swarnalata Saraf
Keyword(s):  
Particle Size ◽  
Sustained Release ◽  
Cellulose Acetate ◽  
Rate Constant ◽  
Diclofenac Sodium ◽  
Order Rate Constant ◽  
Anomalous Transport ◽  
First Order ◽  
Sem Study ◽  
Transport Type

Sustained released tablets of diclofenac sodium (DIC) and tizanidine hydrochloride (TIZ) were prepared by using different proportions of cellulose acetate (CA) as the retardant material. Nine formulations of tablets having different proportion of microparticles developed by varied proportions of polymer: drug ratio ‘’i.e.’’; 1:9 -1:3 for DIC and 1:1 – 3:1 for TIZ. Each tablet contained equivalent to 100 mg of DIC and 6mg of TIZ. The prepared microparticles were white, free flowing and spherical in shape (SEM study), with  the particle size varying from 78.8±1.94 to 103.33±1.28 µm and 175.92± 9.82 to 194.94±14.28µm for DIC  and TIZ, respectively.  The first order rate constant K1 of formulations were found to be in the range of  K1 = 0.117-0.272 and 0.083- 0.189 %hr-1for DIC and TIZ, respectively. The value of exponent coefficient (n) was found to be in the range of 0.6328-0.9412  and 0.8589-1.1954 for DIC and TIZ respectively indicates anomalous  to  non anomalous transport type of diffusions among different formulations

Sedimentation of Pb-210 in Laurentian Shield Lakes

1984 ◽  
Vol 19 (2) ◽  
pp. 97-109 ◽  
Author(s):  
R.J. Cornett ◽  
L. Chant ◽  
D. Link
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Rate Constant ◽  
Bottom Sediments ◽  
Atmospheric Fallout ◽  
Small Lakes ◽  
Fractional Rate ◽  
Total Input ◽  
Shield Lakes ◽  
Annual Flux

Abstract The average annual flux of Pb-210 from the atmosphere to lake surfaces and to the bottom sediments was measured in seven small lakes located on the Laurentian Shield. Direct atmospheric fallout of Pb-210 was 136 ± 16 Bq m-2 a-1 Streams from the lakes' catchments input an additional 5 to 473 Bq m-2 a-1. Only 16 to 80 percent of the total input was found in the lake sediments. The fractional rate constant for Pb-210 sedimentation from the water column ranged from 0.25 to 5.3 per annum.

Formation of CT complexes and electron transfer from excited molecules of anthracene derivatives to methylviologen in aqueous and micellar media

1987 ◽  
Vol 52 (7) ◽  
pp. 1658-1665
Author(s):  
Viktor Řehák ◽  
Jana Boledovičová
Keyword(s):  
Electron Transfer ◽  
Complex Formation ◽  
Fluorescence Quenching ◽  
Rate Constant ◽  
Formation Constants ◽  
Dynamic Quenching ◽  
Micellar Media ◽  
Complex Formation Constants ◽  
Anthracene Derivatives ◽  
Ct Complexes

Disodium 1,5- and 1,8-anthracenedisulphonate (ADS) and 9-acetylanthracene form coloured CT complexes with methylviologen (MV2+) in aqueous and micellar media. The complex formation constants and molar absorptivities were determined by the Benesi-Hildebrandt method. In the fluorescence quenching, its static component plays the major role. The dynamic quenching component is determined by the rate constant of electron transfer from the S1 state of ADS to MV2+.

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