Acclimation of Chlamydomonas reinhardtii to extremely strong light

Most photosynthetic organisms are sensitive to very high light, although acclimation mechanisms enable them to deal with exposure to strong light up to a point. Here we show that cultures of wild-type Chlamydomonas reinhardtii strain cc124, when exposed to photosynthetic photon flux density 3000 μmol m−2 s−1 for a couple of days, are able to suddenly attain the ability to grow and thrive. We compared the phenotypes of control cells and cells acclimated to this extreme light (EL). The results suggest that genetic or epigenetic variation, developing during maintenance of the population in moderate light, contributes to the acclimation capability. EL acclimation was associated with a high carotenoid-to-chlorophyll ratio and slowed down PSII charge recombination reactions, probably by affecting the pre-exponential Arrhenius factor of the rate constant. In agreement with these findings, EL acclimated cells showed only one tenth of the 1O2 level of control cells. In spite of low 1O2 levels, the rate of the damaging reaction of PSII photoinhibition was similar in EL acclimated and control cells. Furthermore, EL acclimation was associated with slow PSII electron transfer to artificial quinone acceptors. The data show that ability to grow and thrive in extremely strong light is not restricted to photoinhibition-resistant organisms such as Chlorella ohadii or to high-light tolerant mutants, but a wild-type strain of a common model microalga has this ability as well.

STUDY OF POLYCONDENSATION PROCESS OF CARBAMIDE WITH FORMALDEHYDE TO RECEIVE BIODEGRADABLE POLYMERS

Biodegradation of polymers of spatial structure is complicated at the impact of soil destructive microorganisms and biodegradation requires long time. We have implemented target-oriented synthesis of a polymer to receive linear structure polymers where labile peptide bonds are preserved.To implement target-oriented synthesis of a polymer and to determine optimal conditions for reaction mechanism we studied the process of kinetics and its regularities – reaction temperature, duration, components ratio, concentration, reaction speed constant and activation energy. The Arrhenius factor and succession of introduction of initial components to the reaction medium were computed, catalyst nature and other properties were determined.High effect of prolongation was achieved, when carbamide and formaldehyde molar ratio was 1:1. In this case linear structure polymer is formed where peptide -CH2 – NH – are preserved.The simplified structure of linear polymer is expressed as followed: – HNCONHCH2[ NHCONHCH2 ]n – HNCONHCH2 – .

Photodegradation of 2, 4, 5, 6-Tetrachloroisophthalonitrile (Chlorothalonil) by Visible and Ultraviolet Light in the Presence of ZnO and TiO2

photocatalytic degradation of fungicides (chlorothalonil) in suspension aqueous solution with semiconductors (tio­2, zno) and without semiconductor has been investigated. the influence of different parameters such as light sources, the concentration of fungicides, type of semiconductors and temperature were studied by uv-visible spectrophotometer at 232 and 254 nm. the degradation reaction order spectra of chlorothalonil were determined which first order at 232 nm and second order at 254 nm. in addition, the rate constant, arrhenius factor and energy of activation can be estimated for both peaks. moreover, conductivity of chlorothalonil has been recorded during the photo-degradation and the rate of reaction also has been determined that dependent on product formation.

Response to Comment on “Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins”

Horner and Pohl argue that high water transport rates reported for carbon nanotube porins (CNTPs) originate from leakage at the nanotube-bilayer interface. Our results and new experimental evidence are consistent with transport through the nanotube pores and rule out a defect-mediated transport mechanism. Mechanistic origins of the high Arrhenius factor that we reported for narrow CNTPs at pH 8 require further investigation.

Formation of Ti5Si3 by Combustion Synthesis in a Self-Propagating Mode: Experimental Study and Numerical Simulation

Titanium silicide (Ti5Si3) was fabricated by self-propagating high-temperature synthesis (SHS) from the elemental powder compact. With the increase of sample density from 50 to 60% TMD, experiments showed that the flame-front velocity increased from 28 to 50 mm/s and combustion temperature from 1,580 to 1,700°C. Based on their dependence, the activation energy of the synthesis reaction, Ea=193 kJ/mol, was deduced. By numerical simulation of combustion wave kinetics, the Arrhenius factor of the rate function, K0=3×109 s−1, was determined for the 5Ti + 3Si reaction system. The effect of sample compaction density on the SHS process was correlated to the variation of the effective thermal conductivity (keff) of the powder compact. The ratio of keff/kbulk=0.02–0.05 was numerically obtained for the 5Ti + 3Si samples with 50–60% TMD and well validated by the experimental data.

Evaluation of the Thermal Stability of Biofuel Obtained from Oil Plant Pyrolysis and Animal Fat

The present study reports obtaining biofuel by pyrolysis of plant oil and animal fat. This process consists in breaking of molecules at high temperatures, obtaining hydrocarbons, similar to oil, and oxygenates such as esters, carboxylic acids, aldehydes, etc. The research aimed to evaluate the thermal and kinetic behaviour and the heat of combustion of bio-oil and bio-oil mixtures / diesel oil. In this work, Thermogravimetric studies were performed (TG) at a heating rate of 10 ° C min-1 under air atmosphere synthetic, Thermodynamic studies (ΔH, ΔS and ΔG) and about heat of combustion also were done. Thermal stability at 30°C was observed from thermogravimetric study. The kinetic calculations were performed in order to observe parameters such as activation energy (Ea) and Arrhenius factor.

Asymmetric solutions of the reaction-diffusion equation

A class of new, non-symmetric solutions are computed for the reaction-diffusion equation (the Bratu problem) governed by the partial differential equation Δ θ + Є e θ /(1+ µθ ) = 0 in a two-dimensional, rectangular domain where µ is the Arrhenius factor and Є is the Frank–Kamenetskii parameter. When µ = 0 previously computed solutions that conform to the expected symmetries are confirmed. In addition, certain hitherto unknown solution branches are found. These appear to be disconnected from the primary branch with in the parameter region investigated here. Each of these asymmetric solution branch contains an additional limit point. These additional solutions do not conform to the expected symmetries and hence they occur with multiplicities of four. Grid refinement tests and extrapolation to zero grid size indicate that these non-symmetric solutions remain distinct, indicating that they are not spurious solutions of a poorly resolved grid. Next a perturbed Bratu problem is examined with convection as an additional heat transport mechanism and Rayleigh number, Ra and tilt angle, ϕ as additional parameters. This variation is examined using both a regular perturbation series expansion in Ra around the conduction state and, a full numerical solution. All of the newly computed solutions at Ra = 0 remain smoothly connected as Ra is increased, which is viewed as an additional evidence in support of the claim that the non-symmetric solutions are real. Even for extremely small convection ( Ra = 5), the quenching effect of convection is significant in both extending the range of stable solutions in Є and in reducing the mean temperature of the region. The quenching effect of the convection in turn reduces the sharp temperature gradients thus making the limit points less sensitive to grid refinement in the presence of weak convection.