Kinetic Parameter

Ubiquinone-10 (CoQ10), a vitamin-like lipophilic component of the membrane-bound electron transport system, has a wide range of therapeutic, neutraceutical, and cosmeceutical applications. The objective of this study was to optimize nutritional requirements for production of CoQ10 by Paracoccus dinitrificans NRRL B-3785 fermentation. Effect of type and concentration of carbon and nitrogen source on fermentation kinetic parameters were analyzed using logistic and Luedeking-Piret equations. In submerged batch fermentation, yield of CoQ10 was 12.22 mg/L when 40 g/L glycerol was used and specific growth rate (0.056/h) as well as growth associated constant (α=0.680 mg/g) were higher as compared to other concentrations. Ammonium nitrate and proteose peptone at 5 (α=0.677 mg/g; β= 0.0072 mg/g·h) and 20 g/L (α=0.806 mg/g; β=0.0074 mg/g·h), respectively, were optimal for CoQ10 production. CoQ10 formation observed to be both growth and nongrowth associated. In optimized medium CoQ10 formation increased considerably from 1.91 to 14.12 mg/L.

The photochemical behavior of oxyfluorfen [2-chloro-1-(3-etoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] on two Greek soils was investigated. Soils were sampled from Nea Malgara and Preveza regions, characterized by a different organic matter content. Soils were spiked with the diphenyl-ether herbicide and irradiation experiments were performed either in the laboratory with a solar simulator (xenon lamp) or outside, under natural sunlight irradiation; other soil samples were kept in the dark to control the retention reaction. Kinetic parameters of both retention and photochemical reactions were calculated using zero-, first- and second- (Langmuir-Hinshelwood) order equations, and best fit was checked through statistical analysis. The soil behaviors were qualitatively similar but quantitatively different, with the soil sampled from the Nea Malgara region much more sorbent as compared with Preveza soil. All studied reactions followed second-order kinetics and photochemical reaction...

Following new trends we applied oxygen uptake rate (OUR) tests as well as long-term tests (in two batch bioreactors systems) in order to assess the biodegradability of textile wastewater. Effluents coming from a dyeing factory were divided into two streams which differed in inorganic and organic contaminants loads. Usefulness of the stream division was proved. Biodegradation of the low-loaded stream led to over 97% reduction of biochemical oxygen demand (BOD 5) together with 80% reduction of chemical oxygen demand (COD) and total organic carbon (TOC). Most of the controlled parameter values were below the levels allowed by legislation for influents to surface water, whereas the high-loaded stream was so contaminated with recalcitrant organic compounds that despite the reduction of BOD 5 by over 95%, COD, TOC, total nitrogen and total phosphorus levels exceeded permissible values. OUR tests were aimed at determination of the following kinetic parameters: maximum specific growth rate (μ Max), half-saturation constant, hydrolysis constant and decay coefficient for activated sludge biomass for both types of textile wastewater studied. The values of kinetic parameters will be applied in activated sludge models used for prediction and optimisation of biological treatment of textile wastewater.

In a placebo-controlled, double-blind study we evaluated the safety and kinetics of a new narcotic antagonist, nalmefene, after 2, 6, 12, and 24 mg intravenous doses to healthy men. At each dose level four subjects received active drug and two received placebo. The drug was well ...

The hydrogenation of maleic acid was investigated using a bimetallic Ru–Re/C catalyst powder in a semi-batch stirred slurry reactor with the main objective of developing a kinetic model that would provide reliable predictions of the observed reactant and product ...

Cu(II) complexes of 3-[4′-dimethylaminophenyl]-1-(2-pyridyl) prop-2-en-1-one (DMAPP) are prepared and characterized by elemental analysis as well as spectral studies (IR and UV–vis), ESR, magnetic susceptibilities and thermal studies. The effect of different alcoholic solvents as well as the temperature on the complex formation is studied. The effect of Cu(II) ion on the emission spectrum of the free chalcone is also assigned.

Unsteady extinguishment phenomena of laminar methane-air co-flow diffusion flames formed in a cup-burner apparatus at normal earth gravity have been studied experimentally and computationally. A gaseous fire-extinguishing agent (CO2, N2, He, Ar, or CF3H) was introduced gradually into a coflowing oxidizer stream until blowoff-type extinguishment occurred. The agent concentration in the oxidizer required for extinguishment was nearly independent of a wide range of the mean oxidizer velocity, exhibiting a so-called plateau region, for all agents except helium. Numerical simulations with detailed chemistry were performed to reveal the detailed flame structure and to predict the minimum extinguishing concentration (MEC) of agent at a fixed oxidizer velocity for a comparison with the experiment previously conducted. The MEC values of agents determined were: experiment: CF3H, (11.7 ± 0.8) %; CO2, (15.7 ± 0.6) %; N2, (25.9 ± 1.0) %; He, (26.7 ± 1.1) %; and Ar, (37.3 ± 1.5) %; computation: C...

The optimum experimental design for determining the kinetic parameters of the model resulting from the Weibull probability density function was studied, by defining the sampling conditions that lead to a minimum confidence region of the estimates, for a number of observations equal to the number of parameters. It was found that for one single isothermal experiment the optimum sampling times corresponded always to fractional concentrations that are irrational numbers (approximately 0.70 and 0.19) whose product is exactly . The experimental determination of the equilibrium conversion (for growth kinetics) is very important, but in some situations this is not possible, e.g. due to product degradation over the length of time required. Sampling times leading to a maximum precision were determined as a function of the maximum conversion (or yield) attainable. For studies of kinetic parameters over a range of temperatures, performed with a minimum of three isothermal experiments, it was proved that the optimum design consists of two experiments at one limit temperature with two sampling times (those corresponding to fractional concentrations of approximately 0.70 and 0.19) and another at the other limit temperature for a sampling time such that the fractional concentration is . Case studies are included for clarification of the concepts and procedures.