Determination of domain distribution by analysis of LEED beam profiles

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Diffuse LEED intensities of disordered crystal surfaces : III. LEED investigation of the disordered (110) surface of gold

The LEED pattern of clean (101) surfaces of Au show a characteristic (1 × 2) superstructure. The diffuseness of reflections in the reciprocal [010] direction is caused by one-dimensional disorder of chains, strictly ordered into spatial [10 ] direction. There is a transition from this disordered superstructure to the normal (1 × 1) structure at 420 + 15°C. The angular profiles of the and (01) beam are measured at various temperatures and with constant energy and angles of incidence of the primary beam. The beam profiles are deconvoluted approximately with the instrument response function

Diffuse LEED intensities of disordered crystal surfaces : II. Multiple scattering on disordered overlayers

The diffraction of low energy electrons from disordered overlayers adsorbed on ordered substrates is treated theoretically by an extension of Beeby's multiple scattering method. A lattice gas model is assumed for the disordered adsorbate layer. Multiple scattering within a certain area around each atom — each atom of the overlayer and within the ordered substrate — is treated self-consistently, the remaining contributions to the total scattering amplitude being averaged. The theory can be used in the limiting cases of random distribution and of long range order within the adsorbate layer

Diffuse LEED intensities of disordered crystal surfaces : IV. Application of the disorder theory

The principles of the statistical disorder theory are discussed briefly. The theory is applied to a model of the disordered (101)Au surface with the characteristic (1 × 2) supersstructure. A fit procedure is described, by which the experimental angular intensity profiles are used directly to determine the disorder parameters and the interaction energies between the chains of surface atoms

Diffuse LEED intensities of disordered crystal surfaces : I. Correlations between statistics and multiple diffraction

It is shown that the diffraction of slow electrons from disordered crystal surfaces is correlated with the problem of thermodynamical statistics. The correlation functions are completely determined by the self-energies and interaction energies of neighboring complexes. These quantities solve the problem of a-priori probabilities and the cooperative phenomenon of correlation functions of these complexes. If the calculation of a certain set of multiple scattering amplitudes is possible, the remaining problem of determining the diffuse LEED pattern becomes solvable. The calculation of angular beam profiles follows the same lines as already described for the kinematic theory of X-ray diffraction

Structure determination of the reconstructed Au(110) surface

The LEED pattern of the Au(110) surface shows a (1 × 2) and also a (1× 3) superstructure. The (1 × 2) superstructure has been determined by comparison of LEED intensities with model calculations. The missing row model is the most probable model. A minimum of the averaged r-factor, , has been found for 15% contraction of the first layer spacing without atomic displacements in the second layer

All-Atom Modeling of Protein Folding and Aggregation

Theoretical investigations of biorelevant processes in the life-science research require highly optimized simulation methods. Therefore, massively parallel Monte Carlo algorithms, namely MTM, were successfully developed and applied to the field of reversible protein folding allowing the thermodynamic characterization of proteins on an atomistic level. Further, the formation process of trans-membrane pores in the TatA system could be elucidated and the structure of the complex could be predicted

Züchtung von orientierten lithiumflourid-einkristallen aus der dampfphase

A high vacuum oven was constructed to grow LiF single crystals from the vapor phase by the vertical pulling method. Using a special crucible top it is possible to grow oriented single crystals of 23 mm diameter and 70 mm length. At a temperature of about 150 °C above the melting point the maximum pulling rate was found to be 8 mm/h. The purification effect of the sublimation was investigated for Na+-, K+-, Ca++-ions and it was found that the concentration of these impurities is of the order of 10-6, except for sodium for which the purification is much less effective

Mammalian cell perfusion cultures: “Intensification by growth inhibition”

Mammalian cell perfusion processes have regained the focus of attraction for the production of therapeutic proteins, especially as a part of an end-to-end integrated production facility. Besides reduced equipment size, higher volumetric productivities, and enhanced cost efficiency, continuous processes enable stable and steady state operation giving more homogeneous and even improved product quality. However, the knowledge on time and cost effective development and scale-up procedures to obtain a stable process operation and desired product quality control is still limited. The combination of long process duration and the lack of automated high-throughput systems for perfusion demand for an optimized strategy regarding the development and control of these processes. In this study, mammalian cell perfusion cultures have been performed targeting high volumetric productivities and enhanced process and product quality control. Shake tube cultures revealed suitable starting conditions (cell specific perfusion rate, media composition, flow rates) for process design and control. Different strategies for minimizing cellular growth were tested: a) minimizing cell specific perfusion rate, b) chemical growth inhibition c) environmental growth inhibition by lowering the culture temperature. Active growth inhibition targeted cell cycle arrest to reduce cellular growth and to trigger higher productivities. The loss of product in the bleed was effectively reduced by all strategies. Especially, lower culture temperatures were an effective tool for process intensification leading to increased cellular productivities and reduced cellular growth, while the use of a chemical inhibitor did not lead to higher protein quantities. Flow cytometry revealed that more cells were arrested in the G1 phase, leading to lower cell proliferation. Resulting product quality patterns remained constant within each operation set point and indicated the possibility of enhanced product quality during perfusion cell cultures. A variety of tools can be used to intensify continuous cultures. A temperature down-shift at the start of the production phase represents the most promising tool for process intensification. The different steps present a systematic and efficient procedure for the development of perfusion cell cultures targeting optimal process performance and tunable product quality control