Application of first order rate kinetics to explain changes in bloom toxicity——the importance of understanding cell toxin quotas

Cyanobacteria are oxygenic photosynthetic Gram-negative bacteria that can form potentially toxic blooms in eutrophic and slow flowing aquatic ecosystems. Bloom toxicity varies spatially and temporally, but understanding the mechanisms that drive these changes remains largely a mystery. Changes in bloom toxicity may result from changes in intracellular toxin pool sizes of cyanotoxins with differing molecular toxicities, and/or from changes in the cell concentrations of toxic and non-toxic cyanobacterial species or strains within bloom populations. We show here how first-order rate kinetics at the cellular level can be used to explain how environmental conditions drive changes in bloom toxicity at the ecological level. First order rate constants can be calculated for changes in cell concentration( μ_c : specific cell division rate) or the volumetric biomass concentration( μ_g : specific growth rate) between short time intervals throughout the cell cycle. Similar first order rate constants can be calculated for changes in nett volumetric cyanotoxin concentration( μ_(tox) : specific cyanotoxin production rate) over similar time intervals. How μ_c(or μ_g) covaries with μ tox over the cell cycle shows conclusively when cyanotoxins are being produced and metabolised, and how the toxicity of cells change in response to environment stressors. When μ_(tox)/μ_c >1, cyanotoxin cell quotas increase and individual cells become more toxic because the nett cyanotoxin production rate is higher than the cell division rate. When μ_(tox)/μ_c =1, cell cyanotoxin quotas remains fixed because the nett cyanotoxin production rate matches the cell division rate. When μ_(tox)/μ_c <1, the cyanotoxin cell quota decreases because either the nett cyanotoxin production rate is lower than the cell division rate, or metabolic breakdown and/or secretion of cyanotoxins is occurring. These fundamental equations describe cyanotoxin metabolism dynamics at the cellular level and provide the necessary physiological background to understand how environmental stressors drive changes in bloom toxicity.

Application of Bronsted acid ionic liquids as green catalyst in the synthesis of 2-propanol with reactive distillation

Five Br?nsted acidic ionic liquids(ILs) were prepared and characterized by FT-IR,~1H NMR and ^(13)C NMR. Their catalytic activities for the synthesis of 2-propanol(IPOH) via transesterification of isopropyl acetate(IPAc) with methanol(Me OH) were investigated. Among all the tested ILs, [Ps-mim]HSO_4 performed best and was used as catalyst for further studies. The reaction kinetics were carried out to correlate the parameters in a homogeneous second order kinetic model. It has been found that there is close agreement between the calculated and experimental values. The high-pressure batch reactive distillation experimental apparatus was set up in order to enhance the conversion of IPAc. A high conversion of IPAc of 99.4% was obtained under the optimal reaction conditions. The catalyst [Ps-mim]HSO_4 can be recycled easily by a rotary evaporator and reused without any further treatment. The catalyst had been repeatedly used for four times and no obvious changes in the structure of catalyst could be observed.

Photodegradation of 4-Chlorobiphenyl in Hexane by UV Irradiation

The photodegradation of 4-chlorobiphenyl in hexane by UV irradiation has been investigated. For the first time, the UV spectral changes of 4-chlorobiphenyl and formation of chloride in the photoreaction have been discussed. The main pathway for the degradation of 4-chlorobiphenyl in hexane was dechlorination to follow a ftrst order kinetics. The products were formed by the cleavage of carbon-chlorine bond to produce a biphenyl free radical, which then abstracted hydrogen from the solvent hexane to form biphenyl. With irradiation, biphenyl was also decomposed to lower hydrocarbons as the final products, which was further confirmed by the degradation experiment of biphenyl.

Test-Particle Simulation of Space Plasmas

Test-particle simulations provide a useful complement to the kinetic simulations of many-body systems and their approximate treatment with multiple moments.In a kinetic approach,systems are described at a microscopic level in terms of a large number of degrees of freedom.Fluid or multiple moment approaches,however,provide a description at the macroscopic level,in terms of relatively few physical parameters involving averages or moments of particle distribution functions.Ideally,fully kinetic descriptions should be done whenever possible.Due to their complexity,the use of these approaches is often not practical in many cases of interest.In comparison,the fluid approximation is much simpler to implement and solve.It can be used to describe complex phenomena in multi-dimensional geometry with realistic boundary conditions.Its main drawback is its inability to account for many phenomena taking place on fine space or time scales,or phenomena involving nonlocal transport.Macroscopic approaches are also not adapted to describe large deviations from local equilibrium,such as the occurrence of particle beams or otherwise strong anisotropy.With the test-particle method,particle trajectories are calculated using approximated fields obtained from a low level approach,such as multiple moments.Approximate fields can also be obtained from experiments or observations.Assuming that these fields are representative of actual systems,various kinetic and statistical properties of the system can then be calculated,such as particle distribution functions and moments thereof.In this paper,the test-particle method is discussed in the context of classical statistical physics of many-body interacting point particles.Four different formulations of the method are presented,which correspond to four broad categories of the application encountered in the field of plasma physics and astronomy.