Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Einfluss fehlpassungsinduzierter Spannungsfelder auf den Transportprozess bei ionischer Leitfähigkeit

Over the last two decades a new route for tailor made functional ceramics has been found in elastic strain engineering. The aim of this thesis was the investigation of the effect of mismatch induced interface strain on the oxygen ion conductivity in yttria stabilized zirconia YSZ. Therefore an analytic model is proposed to describe the elastic strain and stress in columnar thin films. Hereby it is possible to describe the ionic conductivity and the mean lattice plane distance from XRD strain measurements as a function of the layer thickness, and therefore, an estimate of the width of the strained interface region can be given. As a modell system (111)-oriented multilayers of YSZ and a rare earth sesquioxide SE$_{2}$O$_{3}$ (SE =Dy, Y, Er und Sc) have been prepared on (0001) Al$_{2}$O$_{3}$-substrates by pulsed laser deposition. By using different SE$_{2}$O$_{3}$ the interface strain and by changing the deposition parameters the texture of the films can be varied. By measuring the mean lattice distance as a function of the layer thickness using X-Ray diffraction the interface strain release can be nicely visualized. It was able to show that the width of the strained interface region strongly depends on the texture of the films. Values between 3 nm and 10 nm have been determined. The width of the interface increases with increasing degree of texture. The ionic conductivity was determined using electrochemical impedance spectroscopy. However, it needs to be pointed out that the ionic conductivity is both sensitive to the interface strain as well as texture effects and cannot be unequivocally deconvoluted. Samples with only one azimuthal variant showed an unexpected anisotropic conductivity. Samples with a fiber texture did not show this due to a geometric averaging. These highly textured samples exhibited the highest increase in ionic conductivity of up to 400 % when moving down to a film thickness of 100 nm, however the ionic conductivity did not increase monotonousely upon a further decrease of the film thickness. Films with a smaller degree of texture showed the expected monotone change of the ionic conductivity with decreasing film thickness. The width of the strained interface region from these measurements is in accordance with results from the XRD strain measurements. The development of the modell in combination with the texture dependent measurements build a foundation for a better understanding of interfacial strain and its impact on the physicochemical properties of functional ceramics. It was shown that besides the material’s properties the preparation conditions play a crucial role for the strain relaxation and the ionic conductivity, namely inform of the texture and the mean diameter of the columnar crystallites l

Einfluss fehlpassungsinduzierter Spannungsfelder auf den Transportprozess bei ionischer Leitfähigkeit

Over the last two decades a new route for tailor made functional ceramics has been found in elastic strain engineering. The aim of this thesis was the investigation of the effect of mismatch induced interface strain on the oxygen ion conductivity in yttria stabilized zirconia YSZ. Therefore an analytic model is proposed to describe the elastic strain and stress in columnar thin films. Hereby it is possible to describe the ionic conductivity and the mean lattice plane distance from XRD strain measurements as a function of the layer thickness, and therefore, an estimate of the width of the strained interface region can be given.As a modell system (111)-oriented multilayers of YSZ and a rare earth sesquioxide SE2O3 (SE = Dy, Y, Er und Sc) have been prepared on (0001) Al2O3-substrates by pulsed laser deposition. By using different SE2O3 the interface strain and by changing the deposition parameters the texture of the films can be varied. By measuring the mean lattice distance as a function of the layer thickness using X-Ray diffraction the interface strain release can be nicely visualized. It was able to show that the width of the strained interface region strongly depends on the texture of the films. Values between 3 nm and 10 nm have been determined. The width of the interface increases with increasing degree of texture. The ionic conductivity was determined using electrochemical impedance spectroscopy. However, it needs to be pointed out that the ionic conductivity is both sensitive to the interface strain as well as texture effects and cannot be unequivocally deconvoluted. Samples with only one azimuthal variant showed an unexpected anisotropic conductivity. Samples with a fiber texture did not show this due to a geometric averaging. These highly textured samples exhibited the highest increase in ionic conductivity of up to 400 % when moving down to a film thickness of 100 nm, however the ionic conductivity did not increase monotonousely upon a further decrease of the film thickness. Films with a smaller degree of texture showed the expected monotone change of the ionic conductivity with decreasing film thickness. The width of the strained interface region from these measurements is in accordance with results from the XRD strain measurements. The development of the modell in combination with the texture dependent measurements build a foundation for a better understanding of interfacial strain and its impact on the physicochemical properties of functional ceramics. It was shown that besides the material’s properties the preparation conditions play a crucial role for the strain relaxation and the ionic conductivity, namely in form of the texture and the mean diameter of the columnar crystallites l

Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes - An improved model for nanocrystalline thin films and review of experimental data

A phenomenological and analytical model for the influence of strain effects on atomic transport in columnar thin films is presented. A model system consisting of two types of crystalline thin films with coherent interfaces is assumed. Biaxial mechanical strain ε0 is caused by lattice misfit of the two phases. The conjoined films consist of columnar crystallites with a small diameter l. Strain relaxation by local elastic deformation, parallel to the hetero-interface, is possible along the columnar grain boundaries. The spatial extent δ0 of the strained hetero-interface regions can be calculated, assuming an exponential decay of the deformation-forces. The effect of the strain field on the local ionic transport in a thin film is then calculated by using the thermodynamic relation between (isostatic) pressure and free activation enthalpy ΔG#. An expression describing the total ionic transport relative to bulk transport of a thin film or a multilayer as a function of the layer thickness is obtained as an integral average over strained and unstrained regions. The expression depends only on known material constants such as Young modulus Y, Poisson ratio ν and activation volume ΔV#, which can be combined as dimensionless parameters. The model is successfully used to describe own experimental data from conductivity and diffusion studies. In the second part of the paper a comprehensive literature overview of experimental studies on (fast) ion transport in thin films and multilayers along solid–solid hetero-interfaces is presented. By comparing and reviewing the data the observed interface effects can be classified into three groups: (i) transport along interfaces between extrinsic ionic conductors (and insulator), (ii) transport along an open surface of an extrinsic ionic conductor and (iii) transport along interfaces between intrinsic ionic conductors. The observed effects in these groups differ by about five orders of magnitude in a very consistent way. The modified interface transport in group (i) is most probably caused by strain effects, misfit dislocations or disordered transition regions

Potential of VHF-plasmas for low-cost production of a-Si: H solar cells

Compared to the use of the standard glow discharge technique the production of amorphous silicon solar cells by the very high frequency glow discharge (VHF-GD) bears yet additional cost reduction potentials: Using VHF-GD at excitation frequencies higher than 13.56 MHz, a more efficient dissociation of silane gas is obtained; thus, higher deposition rates are achieved; this reduces considerably the deposition time for intrinsic amorphous and microcrystalline silicon layers. Furthermore, by itself and even more so, in combination with argon dilution, VHF-GD technique improves silane utilisation and leads, thus, to further cost reduction. Finally, by combining the VHF-GD technique and the “micromorph” concept “real” tandem cells (i.e. a superposition of two cells with distinctly different band gaps) can be deposited at low temperatures without the use of expensive germane gas