Kinetic models of photosystem II should accommodate the effect of donor side quenching on variable chlorophyll a fluorescence in the microseconds time

Quantitative data on laser flash-induced variable fluorescence in the 100 ns to 1 ms time range (Belyaeva et al. in Photosynth Res 98:105–119, 2008) confirming those of others (Steffen et al. in Biochemistry 40:173–180, 2001, Biochemistry 44:3123–3132, 2005; Belyaeva et al. in Biophysics 51(6):976–990, 2006), need a substantial correction with respect to magnitude of the normalized variable fluorescence associated with single turnover-induced charge separation in RCs of PS II. Their data are conclusive with the involvement of donor side quenching, the release of which occurs with a rate constant in the range of tens of ms-1, and presumed to be associated with reduction of YZ+ by the OE

Induction Kinetics of Photosystem I-Activated P700 Oxidation in Plant Leaves and Their Dependence on Pre-Energization

Absorbance changes ¿A 810 were measured in pea (Pisum sativum L., cv. Premium) leaves to track redox transients of chlorophyll P700 during and after irradiation with far red (FR) light under various preillumination conditions in the absence and presence of inhibitors and protonophorous uncoupler of photosynthetic electron transport. It was shown that cyclic electron transport (CET) in chloroplasts of pea leaves operates at its highest rate after preillumination of leaves with white light and is strongly suppressed after preillumination with FR light. The FR light-induced suppression was partly released during prolonged dark adaptation. Upon FR illumination of dark-adapted leaves, the induction of CET was observed, during which CET activity increased to the peak from the low level and then decreased gradually. The kinetics of P700 oxidation induced by FR light of various intensities in leaves preilluminated with white light were fit to empirical sigmoid curves containing two variables. In leaves treated with a protonophore FCCP, the amplitude of FR light-induced changes ¿A 810 was strongly suppressed, indicating that the rate of CET is controlled by the pH gradient across the thylakoid membran

Analysis of initial chlorophyll fluorescence induction kinetics in chloroplasts in terms of rate constants of donor side quenching release and electron trapping in photosystem II

The fluorescence induction F(t) of dark-adapted chloroplasts has been studied in multi-turnover 1 s light flashes (MTFs). A theoretical expression for the initial fluorescence rise is derived from a set of rate equations that describes the sequence of transfer steps associated with the reduction of the primary quinone acceptor Q A and the release of photochemical fluorescence quenching of photosystem II (PSII). The initial F(t) rise in the hundreds of ¿s time range is shown to follow the theoretical function dictated by the rate constants of light excitation (k L) and release of donor side quenching (k si ). The bi-exponential function shows sigmoidicity when one of the two rate constants differs by less than one order of magnitude from the other. It is shown, in agreement with the theory, that the sigmoidicity of the fluorescence rise is variable with light intensity and mainly, if not exclusively, determined by the ratio between rate of light excitation and the rate constant of donor side quenching release

Licht en leven

Rede 29-11-79 Wageninge

Oxidation and annealing of thin FeTi layers covered with Pd

The hydrogen storage material FeTi has the disadvantage to lose its sorption capacity in contact with impurities such as O and H O. A possibility to overcome this problem is to coat it with an anti-corrosive layer which is permeable for hydrogen. In this study we prepared FeTi layers covered with a 4 or 20 nm thin Pd layer. We used ion beam and sputter profiling techniques, X-ray photoelectron spectrometry and scanning probe techniques to investigate the response of these bi-layers upon annealing up to 3008C in vacuum, air and 10y5 mbar O . The layered structure remains intact up to 150 °C. At 2008C in air and O , Fe and some Ti move towards the Pd surface where they form oxide regions. At higher temperatures thicker oxide regions, presumably along the Pd grains, are formed. These processes are more pronounced for the case of 4 nm Pd. A model is presented to explain the observed phenomena. We conclude that up to 1508C 4 nm of Pd is sufficient to act as a protective layer. For a temperature of 2008C, 20 nm Pd may still provide sufficient protection against oxidation

Анализ эффективности зарезки боковых стволов на скважинах Катыльгинского нефтегазового месторождения (Томская область)

Работа посвящена анализу эффективности зарезки боковых стволов как самому эффективному методу по увеличению нефтеотдачи на Катыльгинском месторождении и рекомендована к применению в дальнейшем. В paбoте пpиведены cведения o геoлoгo-физичеcкoй и геoлoгo-пpoмыcлoвoй хapaктеpиcтике меcтopoждения, aнaлиз paзpaбoтки меcтopoждения, пoкaзaтели текущегo cocтoяния paзpaбoтки и востоновления скважин разными методами. Пpедcтaвленa cтpуктуpa фoндa cквaжин, oбopудoвaнных электpoцентpoбежными нacocaми. Пpoделанные paбoты пoкaзaли, чтo внедpение данного метода (закрезки боковых стволов) пoзвoляет увеличить дoбычу нефти из бездействующих скважин пpи cнижении ее cебеcтoимocти.The work is devoted to the analysis of the effectiveness of sidetracking as the most effective method for increasing oil recovery at the Katylginskoye field and is recommended for use in the future. The work contains information on the geological, physical, and geochemical properties of the site, the analysis of the location of the site, the indicators of the current state of the development and the development of wells in various ways. The structure of the wells is presented, which are equipped with electric centrifugal pumps. The completed works showed that the introduction of this method (sidetracking) allows increasing the oil output from idle wells while reducing its self-sufficiency

Broadband enhancement of light emission in silicon slot waveguides

We investigate the light emission properties of electrical dipole emitters inside 2-dimensional (2D) and 3-dimensional (3D) silicon slot waveguides and evaluate the spontaneous emission enhancement (F_p) and waveguide coupling ratio (β). Under realistic conditions, we find that greater than 10-fold enhancement in F_p can be achieved, together with a β as large as 0.95. In contrast to the case of high Q optical resonators, such performance enhancements are obtained over a broad wavelength region, which can cover the entire emission spectrum of popular optical dopants such as Er. The enhanced luminescence efficiency and the strong coupling into a limited set of well-defined waveguide modes enables a new class of power-efficient, CMOS-compatible, waveguide-based light sources

Adaptation of photosystem II to high and low light in wild-type and triazine-resistant Canola plants: analysis by a fluorescence induction algorithm

Plants of wild-type and triazine-resistant Canola (Brassica napus L.) were exposed to very high light intensities and after 1 day placed on a laboratory table at low light to recover, to study the kinetics of variable fluorescence after light, and after dark-adaptation. This cycle was repeated several times. The fast OJIP fluorescence rise curve was measured immediately after light exposure and after recovery during 1 day in laboratory room light. A fluorescence induction algorithm has been used for resolution and analysis of these curves. This algorithm includes photochemical and photo-electrochemical quenching release components and a photo-electrical dependent IP-component. The analysis revealed a substantial suppression of the photo-electrochemical component (even complete in the resistant biotype), a partial suppression of the photochemical component and a decrease in the fluorescence parameter Fo after high light. These effects were recovered after 1 day in the indoor light

An Evaluation of the Fe-N Phase Diagram Considering Long-Range Order of N Atoms in γ'-Fe4N1-x and ε-Fe2N1-z

The chemical potential of nitrogen was described as a function of nitrogen content for the Fe-N phases α-Fe[N], γ'-Fe4N1-x, and ε-Fe2N1-z. For α-Fe[N], an ideal, random distribution of the nitrogen atoms over the octahedral interstices of the bcc iron lattice was assumed; for γ'-Fe4N1-x and ε-Fe2N1-z, the occurrence of a long-range ordered distribution of the nitrogen atoms over the octahedral interstices of the close packed iron sublattices (fcc and hcp, respectively) was taken into account. The theoretical expressions were fitted to nitrogen-absorption isotherm data for the three Fe-N phases. The α/α + γ', α + γ'/γ', γ'/γ' + ε, and γ' + ε/ε phase boundaries in the Fe-N phase diagram were calculated from combining the quantitative descriptions for the absorption isotherms with the known composition of NH3/H2 gas mixtures in equilibrium with coexisting α and γ' phases and in equilibrium with coexisting γ' and ε phases. Comparison of the present phase boundaries with experimental data and previously calculated phase boundaries showed a major improvement as compared to the previously calculated Fe-N phase diagrams, where long-range order for the nitrogen atoms in the γ' and ε phases was not accounted for