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Wird einem Patienten im Notfall keine sofortige Behandlung zuteil, kann dies schwere Schäden oder gar den Tod zur Folge haben. Auch eine angemessene medizinische Versorgung kann an ihre Grenzen stoßen, wenn die Bewältigung psychosozialer Probleme nach einem Notfall nicht ausreichend beachtet wird. Der Zugang zu psychologischen Unterstützungsangeboten nach Notfällen ist teils unzureichend, neue Versorgungsabläufe und -systeme müssen dringend etabliert werden.

In this study, cylindrical grinding of a 42CrMo4 (AISI 4140) steel with varied grinding sequence stages is analyzed regarding the effect of the different loads during multistage grinding up to the resulting final residual stress state and material structure. The grinding process was adjusted in a way to enhance the mechanical load with varying intensity and generate a pronounced compressive residual stress state in the final grinding step. Furthermore, consecutive multistage grinding processes were carried out and investigated. Using a mobile XRD system with a cos α method mounted on a robotic positioning arm, repetitive measurements of the ground surfaces were performed in the machine tool without sample removal, giving information about the surface residual stress development for each step of the process sequence. The information about the surface integrity development and possible effects of the grinding process during each step is relevant for the contact conditions and modification mechanisms which lead to the final surface integrity. It is shown that the final material state, normally accessible in post-process investigations, can also be achieved reliably by sequencing the process into several steps of a regular grinding process and depends strongly on the contact parameters in a non-linear way. It could be shown, that even the spark out step can lead to significant changes in the surface residual stress state.

Laser hardening is a process that modifies not only hardness, but also residual stresses near the surface. However, limited information is available on the effect of multi-cycle phase transformation on the hardness and residual stresses, which could be a possibility to achieve different material modifications. In this paper, the effects of multi-pass laser hardening on the material modifications of quenched and tempered as well as ferrite/pearlite AISI 4140 steel have been investigated. The multi-cycle phase transformation process has been carried out using a continuous wave laser with a rectangular beam shape using different schemes, without heat accumulation between each cycle. Results showed that material properties were modified with accumulation effects within the given pass up to 16 cycles. With increasing passes, it was found that the induced compressive residual stress at the surface decreased despite of the initial material state, while the hardness in the subsurface area and hardening depth increased differently, which depended on the initial heat treatment condition. These results indicated the possibility of tailoring the material hardness and surface residual stress by the given heat treatment condition, laser process and cycle number in the multi-pass laser hardening.

The newly proposed concept of Process Signatures enables the comparison of seemingly different manufacturing processes via a process-independent approach based on the analysis of the loading condition and resulting material modification. This contribution compares the recently published results, based on numerically achieved data for the development of Process Signatures for sole surface and volume heatings without phase transformations, with the experimental data. The numerical approach applies the moving heat source theory in combination with energetic quantities. The external thermal loadings of both processes were characterized by the resulting temperature development, which correlates with a change in the residual stress state. The numerical investigations show that surface and volume heatings are interchangeable for certain parameter regimes regarding the changes in the residual stress state. Mainly, temperature gradients and thermal diffusion are responsible for the considered modifications. The applied surface- and volume-heating models are used in shallow cut grinding and induction heating, respectively. The comparison of numerical and experimental data reveals similarities, but also some systematic deviations of the residual stresses at the surface. The evaluation and final discussion support the assertion for very fast stress relaxation processes within the subsurface region. A consequence would be that the stress relaxation processes, which are not yet included in the numerical models, must be included in the Process Signatures for sole thermal impacts.

Plastic deformations induced by the rolling contact in the deep rolling process are the origin of the formation of residual stress fields and increased dislocation density in the material. The near surface material modification achieved through the process, like a compressive residual stress field, improved hardness and reduced surface roughness, give rise to improved component performance during operation. For a general understanding of the generated surface-near properties, an analysis of single tracks contributing to surface integrity is required. In the present study, a detailed investigation of the achieved residual stress state distribution as well as the local dislocation density of single processed tracks was performed through high spatial resolution X-ray diffraction analyses. Using two spherical deep rolling tools of 6 mm and 13 mm diameter, single tracks were processed with different parameters on samples of steel AISI 4140H. It could be observed that residual stress fields at the surface reach much larger lateral expansion than the plastically deformed track which can be determined by optical measurements, while a correlation with the dislocation density distribution was found. For the maximum dislocation density in the tracks, a correlation with the theoretical maximum equivalent stress was determined. Furthermore, a method to connect the measured dislocation density to the localized plastic strains during processing was applied to exemplary distributions.

The functional performance of workpieces is strongly influenced by the surface and subsurface properties which are affected and can be adjusted by manufacturing processes. The finishing process determines the final form and the surface roughness of a machined component. Nonetheless, the final surface integrity is a result of the total material modification along the whole process chain. Previous manufacturing processes affect the initial residual stress state and the work hardening in the subsurface layers. Furthermore, the resulting material modifications may vary depending on the initial or pre-machined material state. In this paper, the influence of pre-machining processes on the resulting surface integrity after mechanical finishing processes is analyzed. As finishing processes, deep rolling and so called “grind-strengthening” with varied process parameters are chosen. The initial material state is generated by heat treatment followed by pre-machining using three different processes: turning, grinding and electrochemical etching leading to strong variations in the surface-near properties. For the analysis of the influence of initial material state residual stresses as well as the shear stress were considered. Both processes, deep rolling and grind-strengthening, achieve comparable compressive stresses at the surface, whereby the residual stress states can deviate for constant parameters under variation of pre-machining. The residual stress depth profiles show a significant influence of the initial state for the grinding process but minor influence for deep rolling. The investigations contribute to a better understanding of mechanisms causing material modification during mechanical surface treatment and along the process chain.

Stainless steels like X210Cr12 consist of metastable austenite that transforms into martensite when a critical temperature or critical strain is reached. However, the mechanism of martensite formation and the shape and appearance of martensite can differ significantly depending on the used mechanical or thermal pathway. This necessitates a systematic study on the martensitic transformation and twinning of metastable austenite in X210Cr12 after liquid nitrogen cooling, deep rolling and their sequential combinations. The thereby obtained surface modifications were characterized by hardness penetration measurements, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and orientation and phase mapping using automated scanning electron nano-diffraction (SEND). X-Ray diffraction (XRD) was performed to measure residual stresses in the surface near regions of the samples. The here obtained results show that liquid nitrogen cooling yields formation of coarse grained martensite with grain sizes between 1 and 10 μm and deep rolling causes formation of a nanosized microstructure containing martensite and twins. Moreover, the here obtained results suggest that compressive residual stresses of up to −750 MPa together with the martensite/twin nanostructure stabilizes metastable austenite and prevents the formation of large martensite grains in the surface zone during subsequent liquid nitrogen cooling. A substantial hardness increase ranging from 355 HV0.1 up to about 850 HV0.1 was measured for all treatments. The highest value of about 950 HV0.1 was measured after martensite transformation induced by liquid nitrogen cooling.

The deep rolling process is widely used as a finishing step, improving the surface properties through cold working and creation of residual strains. In the present investigations, in situ X-ray diffraction experiments were performed with a self-built deep rolling device at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The measurements were performed with a cylindrical roller-tool on steel samples at beamline ID11 with a monochromatic beam of 50 × 50 µm in transmission. Several properties could be investigated based on the diffraction data. In particular, 2D-strain maps were determined in the range of several millimeters around the deep rolling tool. Based on the data collected during loading and after unloading, knowledge about the transient state leading to the resulting remaining property modifications like residual strains and plastic deformation were generated.

A deep rolling process was applied on 4140H steel specimens with a self-built loading frame and investigated in situ with neutron radiation using the SALSA instrument at the Institut Laue-Langevin (ILL). A neutron diffraction stress imaging approach was developed and used to determine material changes from the surface up to several millimeters inside the material by single expositions. The strains could be evaluated as deviations of the diffraction signal along the height of an area detector, and the theoretical maximum depth resolution was given by geometrical magnification together with the detector pixel size. The results of these experiments together with complementary post-process investigations could be used to link the internal load during the process with resulting material modifications such as the generated residual strains.

30,000 transgenic petunia plants carrying a single copy of the maize A1 gene, encoding a dihydroflavonol reductase, which confers a salmon red flower colour phenotype on the petunia plant, were grown in a field test. During the growing season plants with flowers deviating from this salmon red colour, such as those showing white or variegated phenotypes and plants with flowers exhibiting only weak pigmentation were observed with varying frequencies. While four white flowering plants were shown at the molecular level to be mutants in which part of the A1 gene had been deleted, other white flowering plants, as well as 13 representative plants tested out of a total of 57 variegated individuals were not mutants but rather showed hypermethylation of the 35S promoter directing A1 gene expression. This was in contrast to the homogeneous fully red flowering plants in which no methylation of the 35S promoter was observed. While blossoms on plants flowering early in the season were predominantly red, later flowers on the same plants showed weaker coloration. Once again the reduction of the A1-specific phenotype correlated with the methylation of the 35S promoter. This variation in coloration seems to be dependent not only on exogenous but also on endogenous factors such as the age of the parental plant from which the seed was derived or the time at which crosses were made.

Biological nitrogen fixation is an extremely energy intensive process. Under ideal conditions the reduction of one molecule of dinitrogen (N2), catalysed by the nitrogenase enzyme complex, requires 16 molecules of ATP. However, in vivo ATP requirements of up to 42 per N2 reduced have been measured (80; see 66). It is therefore not surprising that free-living nitrogen-fixing bacteria, such as Klebsiella pneumoniae, only reduce N2 when nitrogen (N-) starved and tightly regulate their nitrogen-fixation (nif) genes in response to the intracellular concentration of combined nitrogen (N-regulation). In the case of symbiotic nitrogen fixing bacteria such as rhizobia, the situation is different. As docile endosymbionts in nodules, having differentiated into a clearly different physiological state (bacteroids), they are provided by the plant host with (ample) carbon (C-) source(s) for the production of ATP and reducing equivalents, to facilitate nitrogen fixation for the plant’s benefit (see 66). Therefore, the nif/fix genes of these bacteria may not need to be subject to N-regulation.

Summary Translational fusions of nitrogen fixation ( nif ) genes to the β-galactosidase ( lacZ ) gene are used to investigate nif gene regulation, in response to different nitrogen sources and oxygen concentrations, to free living nitrogen fixing cultures of Azorhizobium caulinodans ORS571. Derepression of nif gene promoters is also examined in nitrogen fixing stem- and root nodules induced on Sesbania rostrata . The effect of increasing nitrate concentrations on nodulation and nitrogen fixation is determined. These results are reviewed in the light of recent progress in understanding the structure, function and regulation of nitrogen fixation and assimilation genes of A. caulinodans ORS571.