58 research outputs found

    Electron transfer and arrangement of the redox cofactors in photosystem I

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    Measuring the deliverable and impressible dimensions of service experience

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    Service innovation has become a priority within the field of innovation management and is increasingly focused on creating memorable experiences that can result in customer loyalty. Studies of experience design suggest individual service elements to be managed when staging an experience, whereas conceptual models in the literature emphasize the holistic way in which an experience is perceived. In short, service experience is greater than the sum of its parts. Therefore, successful innovation management requires the ability to understand and measure the mechanisms by which service innovations impact customers' experiences. Our research addresses this need by identifying dimensions of service experience and developing a tool for their measurement. Using a three stage process of systematic literature review, rigorous scale development and reduction, and validation, we identify six dimensions of the service experience and develop scales to measure each one. This results in a model of service innovation that highlights the levers through which a company's service innovation efforts can result in memorable experiences and ultimately new service success

    Weak temperature dependence of P (+) H A (-) recombination in mutant Rhodobacter sphaeroides reaction centers

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    International audienceIn contrast with findings on the wild-type Rhodobacter sphaeroides reaction center, biexponential P (+) H A (-) → PH A charge recombination is shown to be weakly dependent on temperature between 78 and 298 K in three variants with single amino acids exchanged in the vicinity of primary electron acceptors. These mutated reaction centers have diverse overall kinetics of charge recombination, spanning an average lifetime from ~2 to ~20 ns. Despite these differences a protein relaxation model applied previously to wild-type reaction centers was successfully used to relate the observed kinetics to the temporal evolution of the free energy level of the state P (+) H A (-) relative to P (+) B A (-) . We conclude that the observed variety in the kinetics of charge recombination, together with their weak temperature dependence, is caused by a combination of factors that are each affected to a different extent by the point mutations in a particular mutant complex. These are as follows: (1) the initial free energy gap between the states P (+) B A (-) and P (+) H A (-) , (2) the intrinsic rate of P (+) B A (-) → PB A charge recombination, and (3) the rate of protein relaxation in response to the appearance of the charge separated states. In the case of a mutant which displays rapid P (+) H A (-) recombination (ELL), most of this recombination occurs in an unrelaxed protein in which P (+) B A (-) and P (+) H A (-) are almost isoenergetic. In contrast, in a mutant in which P (+) H A (-) recombination is relatively slow (GML), most of the recombination occurs in a relaxed protein in which P (+) H A (-) is much lower in energy than P (+) H A (-) . The weak temperature dependence in the ELL reaction center and a YLH mutant was modeled in two ways: (1) by assuming that the initial P (+) B A (-) and P (+) H A (-) states in an unrelaxed protein are isoenergetic, whereas the final free energy gap between these states following the protein relaxation is large (~250 meV or more), independent of temperature and (2) by assuming that the initial and final free energy gaps between P (+) B A (-) and P (+) H A (-) are moderate and temperature dependent. In the case of the GML mutant, it was concluded that the free energy gap between P (+) B A (-) and P (+) H A (-) is large at all times

    FLASH ABSORPTION SPECTROSCOPY. PRINCIPLE AND APPLICATIONS IN PLANT PHOTOSYNTHESIS RESEARCH

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    [Ru(bpy)3]2+ as a reference in transient absorption spectroscopy: differential absorption coefficients for formation of the long-lived 3MLCT excited state

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    International audienceTransient absorption spectroscopy and other time-resolved methods are commonly used to study chemical reactions and biological processes induced by absorption of light. In order to scale the signal amplitude or to compare results obtained under different conditions, it is advisable to use a reference system, a standard of convenient and well-defined properties. Finding Tris(bipyridine)ruthenium(II), [Ru(bpy)3]2+, a suitable candidate for a transient-absorption spectroscopy reference due to its favourable photochemical properties, we have determined accurate relative values of differential molar absorption coefficients (Δε) for light-induced formation of the metal-to-ligand charge transfer (MLCT) excited triplet state at several relevant wavelengths (wavelengths of commercially available lasers) in the UV and visible regions. We have also attempted to determine the absolute value of Δε close to the wavelength of maximum bleaching (∼450 nm) and we propose to narrow down the interval of conceivable values for Δε450 from the broad range of published values (−0.88 × 10^4 M−1cm−1 to −1.36 × 10^4 M−1cm−1) to −1.1 × 10^4 M−1cm−1 ± 15%. Having ourselves successfully applied [Ru(bpy)3]2+ as a standard in a recent time-resolved study of enzymatic DNA repair, we would like to encourage other scientists to use this convenient tool as a reference in their future spectroscopic studies on time scales from picoseconds to hundreds of nanoseconds
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