scholarly journals Rhodopsin photoproducts and rod sensitivity in the skate retina.

1977 ◽  
Vol 69 (1) ◽  
pp. 97-120 ◽  
Author(s):  
K P Brin ◽  
H Ripps
Keyword(s):  
Experimental Data ◽  
Computer Simulation ◽  
Rate Constants ◽  
Dark Adaptation ◽  
Photochemical Reactions ◽  
The Other ◽  
Thermal Reactions ◽  
Rate Of Recovery ◽  
Spectral Absorbance ◽  
Kinetics Of

The late photoproducts that result from the isomerization of rhodopsin have been identified in the isolated all-rod retina of the skate by means of rapid spectrophotometry. The sequence in which these intermediates form and decay could be described by a scheme that incorporates two pathways for the degradation of metarhodopsin II (MII) to retinol: one via metarhodopsin III (MIII) and the other (which bypasses MIII) through retinal. Computer simulation of the model yielded rate constants and spectral absorbance coefficients for the late photoproducts which fit experimental data obtained at temperatures ranging from 7 degrees C to 27 degrees C. Comparing the kinetics of the thermal reactions with the changes in rod threshold that occur during dark adaptation indicated that the decay of MII and the fall in receptor thresholds exhibit similarities with regard to their temperature dependence. However, the addition of 2 mM hydroxylamine to a perfusate bathing the retina greatly accelerated the photochemical reactions, but had no significant effect on the rate of recovery of rod sensitivity. It appears, therefore, that the late bleaching intermediates do not control the sensitivities of skate rods during dark adaptation.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

Mechanodestruction of Isoprene Rubber. Part 1. Process Kinetics

2021 ◽  
Vol 80 (3) ◽  
pp. 118-122
Author(s):  
V.P. Dorozhkin ◽  
◽  
E.G. Mokhnatkina ◽  
D.N. Zemsky ◽  
A.D. Valiev ◽  
...  
Keyword(s):  
Experimental Data ◽  
Molecular Mass ◽  
Rate Constants ◽  
Oxidative Destruction ◽  
Process Kinetics ◽  
Mass Fractions ◽  
Rubber Part ◽  
Kinetics Of ◽  
Selection Of ◽  
Isoprene Rubber

A method is proposed that allows us to obtain the values of the rate constants (CR) of the processes of mechanodestruction (mechanical cracking) of kм, oxidative destruction of kо, and recombination of kр macromolecules, as well as the mass fractions of the corresponding fractions of φм, φо, and φр,r involved in the plasticization process (P) of SKI-3 isoprene rubber. The method is based on the selection of the values of these parameters that correspond to the previously obtained experimental data, using the previously obtained recurrent equations and a specially developed program. The dependences of the CR on the time P at 30oC are obtained, which allows us to describe the kinetics of the processes accompanying P at this temperature, and the changes in molecular mass (MM) in this process. It is shown that constant values of CR are established at large times of P. Refined explanations of the nature of the kinetics of the CR change at P are proposed. The MM value of SKI-3 macromolecules that have not undergone destruction is calculated, depending on the time of plasticization.

Benzhydrylium and tritylium ions: complementary probes for examining ambident nucleophiles

2015 ◽  
Vol 87 (4) ◽  
pp. 341-351 ◽  
Author(s):  
Armin R. Ofial
Keyword(s):  
Free Energy ◽  
Rate Constants ◽  
The Other ◽  
Steric Effects ◽  
Linear Free Energy Relationship ◽  
Reliable Tool ◽  
Linear Free Energy ◽  
Sensitivity Parameter ◽  
Meldrum's Acids ◽  
Kinetics Of

AbstractThe linear free energy relationship log k = sN(N + E) (eq. 1), in which E is an electrophilicity, N is a nucleophilicity, and sN is a nucleophile-dependent sensitivity parameter, is a reliable tool for predicting rate constants of bimolecular electrophile-nucleophile combinations. Nucleophilicity scales that are based on eq. (1) rely on a set of structurally similar benzhydrylium ions (Ar2CH+) as reference electrophiles. As steric effects are not explicitely considered, eq. (1) cannot unrestrictedly be employed for reactions of bulky substrates. Since, on the other hand, the reactions of tritylium ions (Ar3C+) with hydride donors, alcohols, and amines were found to follow eq. (1), tritylium ions turned out to be complementary tools for probing organic reactivity. Kinetics of the reactions of Ar3C+ with π-nucleophiles (olefins), n-nucleophiles (amines, alcohols, water), hydride donors and ambident nucleophiles, such as the anions of 5-substituted Meldrum’s acids, are discussed to analyze the applicability of tritylium ions as reference electrophiles.

scholarly journals NICKEL BIOSORPTION BY FINELY GROUND WASTE SLUDGE / NIKELIO BIOSORBAVIMAS SMULKIAI SUMALTU NUOTEKŲ DUMBLU / БИОСОРБЦИЯ НИКЕЛЯ МЕЛКО ИЗМЕЛЬЧЕННЫМ ИЛОМ СТОКОВ

2011 ◽  
Vol 19 (3) ◽  
pp. 208-214 ◽  
Author(s):  
Yasser Hannachi
Keyword(s):  
Experimental Data ◽  
Langmuir Isotherm ◽  
Treatment Plant ◽  
Second Order ◽  
The Other ◽  
Biosorption Capacity ◽  
Waste Sludge ◽  
Order Rate ◽  
Kinetics Of ◽  
Better Than

In this paper, removal of Ni (II) from aqueous solution by finely ground waste sludge (FGWS) was investigated. Waste sludge samples obtained from a varnishes and lacquers industry wastewater treatment plant was dried, ground and pre-treated with 1% H2O2 to improve the biosorption capacity. Kinetics of nickel biosorption onto FGWS was investigated by using the FGWS samples with particle size of 62.2 µm. The pseudo-first and second order rate expressions were used to correlate the experimental data. The kinetic constants were determined for both models and the second order rate expression was found to be more suitable. Three different biosorption isotherms were used to correlate the equilibrium biosorption data and the isotherm constants were determined. The Langmuir isotherm was found to fit the experimental data better than the other tested isotherms. The biosorption capacity (qm) and saturation constant (K) for the Langmuir isotherm showed that finely ground waste sludge has the largest capacity and affinity for removal of Ni(II) compared to the other Activated sludges. Santrauka Nagrinėjami Ni(II) šalinimo iš vandeninių tirpalų smulkiai sumaltu nuotekų dumblu (SSND) tyrimų rezultatai. Nuotekų dumblo pavyzdžiai imti iš glazūravimo ir lakavimo pramonės nuotekų valymo įrenginių, išdžiovinti, susmulkinti ir apdoroti 1% H2O2, kad padidėtų biosorbcijos tūris. Nikelio sorbcijos SSND kinetika tirta naudojant SSND bandinius, kurių dalelių dydis 62,2 µm. Pseudo pirmojo ir antrojo laipsnio greičio išraiškos buvo taikomos eksperimentinių duomenų koreliacijai apibrėžti. Kinetinė konstanta nustatyta abiejų modelių, tačiau antrojo laipsnio greičio išraiška buvo tinkamesnė. Pagal tris skirtingas biosorbcijos izotermes nustatyta biosorbcijos pusiausvyros duomenų koreliacija, rastos izotermių konstantos. Langmiuro (Langmuir) izotermė geriau atitiko eksperimentinius duomenis nei kitos tirtosios izotermės. Pagal Langmiuro izotermę biosorbcijos geba (q m) ir prisotinimo konstanta (K) rodė, kad smulkiai sumalto nuotekų dumblo geba šalinti Ni(II) yra didžiausia, palyginti su kitos rūšies aktyvintojo dumblo. Резюме Исследуется удаление Ni(II) из водных растворов мелко измельченным илом стоков (МИИС). Образцы ила стоковбыли взяты из оборудования по очистке стоков в промышленности по глазурованию и лакованию. Затем образцы были высушены, измельчены и обработаны 1-процентным H2O2, с целью увеличить объем биосорбции. Кинетика сорбции никеля МИИС исследовалась с применением образцов МИИС, величина частиц которых составляла62,2 μм. Выражения скорости псевдопервой и псевдовторой степени использовались для определения корреляции экспериментальных данных. Кинетическая константа была установлена для обеих моделей. Однако выражение скорости второй степени оказалось более приемлемым. Три разные изотермы биосорбции применялись для определения корреляции данных по равновесию биосорбции и констант изотерм. Изотерма Langmuir лучше совпала с экспериментальными данными, чем другие испытуемые изотермы. Способность биосорбции (q m) изотермы Langmuir и константа насыщения (K) показали, что мелко измельченный ил стоков обладает наибольшей способностью удалять Ni(II) по сравнению с другими видами активированного ила.

The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

THE REACTION OF 2,2-DIPHENYL-1-PICRYLHYDRAZYL WITH SECONDARY AMINES

1958 ◽  
Vol 36 (12) ◽  
pp. 1729-1734 ◽  
Author(s):  
J. E. Hazell ◽  
K. E. Russell
Keyword(s):  
Secondary Amine ◽  
Rate Constants ◽  
Reaction Mechanisms ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Major Product ◽  
The Other ◽  
Secondary Amines ◽  
First Order ◽  
Kinetics Of

The reaction of DPPH (2,2-diphenyl-1-picrylhydrazyl) with N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, diphenylamine, and methylaniline has been studied and has been shown to be primarily a hydrogen abstraction process. Two moles DPPH react with 1–1.15 moles secondary amine to give 1.7–1.8 moles 2,2-diphenyl-1-picrylhydrazine and further products.The reaction between DPPH and N-phenyl-1-naphthylamine is first order with respect to each reactant. The reaction of DPPH with the other amines is retarded by the major product 2,2-diphenyl-1-picrylhydrazine and the kinetics of the over-all reaction are complex. However second-order rate constants and activation energies have been obtained using initial rates of reaction. Possible reaction mechanisms are discussed.

Kinetics of photochemical reactions with excitation by polychromatic radiation

1985 ◽  
Vol 50 (12) ◽  
pp. 2783-2787 ◽  
Author(s):  
Radim Hrdina ◽  
Igor Čepčiansky ◽  
Jaroslav Poskočil
Keyword(s):  
Experimental Data ◽  
Photochemical Reactions ◽  
Quantum Yields ◽  
Calculation Methods ◽  
Quantitative Studies ◽  
Radiation Sources ◽  
Kinetics Of ◽  
Polychromatic Radiation

For quantitative studies of photochemical reactions with low quantum yields the paper suggests application of polychromatic radiation sources whose overall intensity is by orders higher than that of currently available monochromatic sources. The more complicated and laborious calculation methods suggested for treatment of the experimental data can be solved by usual numerical procedures.

Kinetics of renin-antirenin reaction: micromethods for the assay of renin and antirenin

1975 ◽  
Vol 228 (4) ◽  
pp. 973-979 ◽  
Author(s):  
E Haas ◽  
H Goldblatt ◽  
RL Klick ◽  
L Lewis
Keyword(s):  
Experimental Data ◽  
Lower Limit ◽  
Rate Constant ◽  
Rate Constants ◽  
Data Accuracy ◽  
Michaelis Constant ◽  
Renin Substrate ◽  
Method Of Calculation ◽  
Human Renin ◽  
Kinetics Of

Indirect micromethods were designed for the assay of human renin (lower limit 0.25 times 10-4 U and of antirenin to human renin (lower limit 3 times 10-4 U), with the rat used for the bioassay of the angiotensin produced by the action of renin on renin substrate. This made possible the assay of unusually small amounts (0.01 mu1) of serum for antirenin. The Michaelis-Menten concept of a dissociating complex can be applied to the antireninrenin reaction: the rate constants for the formation and for the breakdown of the complex were k1 equal to 1.65 (ml/U antirenin per min) and k3 equal to 1.97 times 10-3 (U inactivated renin/U antirenin per min), respectively; the apparent Michaelis constant was 12 times 10-4 (U renin/ml). A second method of analysis was also applied by assuming the formation of a rather tight complex, with antirenin functioning as an irreversible inactivator of renin. Both methods of analysis yielded practically the same rate constant (k1 equal to 1.65 and k1 equal to 1.71), but the treatment according to the Michaelis-Menten equation affords a slightly better fit of the experimental data (accuracy equal to plus or minus 15.5 percent) than the second method of calculation (accuracy equal to plus or minus 21.6 percent).

Kinetics of the photochemical reactions of the croconate dianion in aqueous solution

1992 ◽  
Vol 70 (1) ◽  
pp. 135-143 ◽  
Author(s):  
B Zhao ◽  
M. H. Back
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Quantum Yield ◽  
Rate Constants ◽  
Photochemical Reactions ◽  
Electron Acceptors ◽  
Basic Solution ◽  
Hydroxyl Ion ◽  
Kinetics Of

The kinetics of the photochemical reactions of the dianion of croconic acid (1,2-dihydroxycyclopentenetrione) have been studied in aqueous solution in the presence of electron acceptors. In neutral solutions the quantum yield for disappearance of croconate dianion was small (< 10−3) but was substantially increased in basic solution and in the presence of electron acceptors. At pH 12 in the presence of 4-nitrobenzylbromide and biacetyl a quantum yield of 1 was obtained. The kinetics of the rate of disappearance of croconate dianion as a function of pH and concentration of acceptor showed that the excited dianion is oxidized by acceptors and reacts with hydroxyl ion. A mechanism is proposed that, by assuming reasonable values for the rate constants involved, is shown to be consistent with the results. Keywords: photolysis, kinetics, croconate dianion, electron transfer.

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