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This study discusses the effects of surface topographies on the frictional behavior of 100Cr6 bearing steel. A solid state laser with nanosecond pulses is used to produce one- and two-dimensional periodic micropatterns using direct laser interference patterning. Line-, cross-, and dot-like patterns with pitches of 5m, and aspect ratios (AR) between 0.02 and 0.17 are fabricated. The friction tests of the surface textured samples are performed under lubricating conditions using a ball-on-disk configuration in rotating mode. The results show that through the surface structure a reduction of the friction coefficient from 25 to 65% can be achieved compared to unstructured surfaces. The smallest coefficients of friction are obtained for ARs between 0.07 and 0.11.

A two-dimensional thermal model for the calculation of temperature distributions, including heat conduction and phase change, for single-pulsed direct laser interference patterning (DLIP) was described. The numerical model was solved by the meshfree smoothed particle hydrodynamics (SPH) method. To obtain a good computational accuracy, the chosen particle distribution must permit several particles within the very short absorption length of the material. The observed influence of the smoothing length on the model accuracy leads to the conclusion that a 21 particle neighbourhood in the particle approximation is suitable. This corresponds to a kernel smoothing length of the 2.4-fold particle spacing in case of an equidistant rectangular particle distribution. Numerical tests provide evidence that a particle discretisation by a local refinement approach is comparable to a fine equidistant discretisation in terms of accuracy. However, employing the locally refined particle distribution leads to a strong reduction of both computation time and memory capacity requirement. The obtained results are in good agreement with results computed using a previous finite element model. An advantage of the SPH thermal model is that the enthalpy discontinuity at the phase transition point is considered. In contrast, existing FEM models of single-pulsed DLIP spread the enthalpy of phase transition over a broader temperature interval, and therefore differences in computed temperature distributions become particularly apparent close to the vaporisation point. Experimental investigations of DLIP were performed on stainless steel substrates. The computations of the adapted model correspond very well to the molten pool dimensions measured and estimated on the basis of the experiments. It is uncertain, though, whether the evaporation noticed in the computational model actually takes place as convection in the molten bath is able to reduce the temperature of the melt considerably. To assess the extent of evaporation and hence the support of the melt displacement by the evaporation-induced recoil pressure the fluid flow in the molten bath has to be accounted for in the model. A noticeable benefit of the meshfree SPH method in contrast to conventional numerical methods is that deformations, tangling and even disintegration of the computational domain do not pose a serious problem. Therefore, the developed model is extendable to investigate the molten bath convection and evaporation during the DLIP process. Considering moderate fluence, the convection is of thermo-capillary nature, that is, strong thermal gradients at the surface of the substrate cause surface tension gradients that induce shear stresses leading to convection. At high fluence, convection is dominated by the evaporation-induced recoil pressure. To understand the mechanisms involved in single-pulsed DLIP of metallic substrates, the effects of molten bath convection and even ablation by material evaporation have to be assessed. Thus, future investigations on modelling DLIP using SPH will include the discussion of fluid flow and evaporation.

Orientation Microscopy in the Transmission Electron Microscope - Investigations of Small Orientations Changes by Means of Orientation Mapping in TEM

Objective. 1H MR spectroscopy (MRS) is widely performed for assessment of brain tumours and is considered a highly sensitive technique capable of differentiating benign from malignant conditions and tumour grading. Method. We present a case of a 69 year old woman who was suspected to have gliomatosis on MRI. Results. MRS performed using single voxel and chemical shift/multivoxel techniques was within normal limits. A repeat scan 6 months later showed progressive disease, and biopsy was performed that proved the diagnosis of glioblastoma. Conclusion. Normal MRS in a patient with suspicion of gliomatosis on MRI should not reassure clinicians into assuming a benign aetiology or a good prognosis in short term.

The most widely used method for detecting genome-wide protein–DNA interactions is chromatin immunoprecipitation on tiling microarrays, commonly known as ChIP-chip. Here, we conducted the first objective analysis of tiling array platforms, amplification procedures, and signal detection algorithms in a simulated ChIP-chip experiment. Mixtures of human genomic DNA and “spike-ins” comprised of nearly 100 human sequences at various concentrations were hybridized to four tiling array platforms by eight independent groups. Blind to the number of spike-ins, their locations, and the range of concentrations, each group made predictions of the spike-in locations. We found that microarray platform choice is not the primary determinant of overall performance. In fact, variation in performance between labs, protocols, and algorithms within the same array platform was greater than the variation in performance between array platforms. However, each array platform had unique performance characteristics that varied with tiling resolution and the number of replicates, which have implications for cost versus detection power. Long oligonucleotide arrays were slightly more sensitive at detecting very low enrichment. On all platforms, simple sequence repeats and genome redundancy tended to result in false positives. LM-PCR and WGA, the most popular sample amplification techniques, reproduced relative enrichment levels with high fidelity. Performance among signal detection algorithms was heavily dependent on array platform. The spike-in DNA samples and the data presented here provide a stable benchmark against which future ChIP platforms, protocol improvements, and analysis methods can be evaluated.