Accurate prediction of melt pool shapes in laser powder bed fusion by the non-linear temperature equation including phase changes - isotropic versus anisotropic conductivity

In this contribution, we validate a physical model based on a transient temperature equation (including latent heat) w.r.t. the experimental set AMB2018-02 provided within the additive manufacturing benchmark series, established at the National Institute of Standards and Technology, USA. We aim at predicting the following quantities of interest: width, depth, and length of the melt pool by numerical simulation and report also on the obtainable numerical results of the cooling rate. We first assume the laser to posses a double ellipsoidal shape and demonstrate that a well calibrated, purely thermal model based on isotropic thermal conductivity is able to predict all the quantities of interest, up to a deviation of maximum 7.3\% from the experimentally measured values. However, it is interesting to observe that if we directly introduce, whenever available, the measured laser profile in the model (instead of the double ellipsoidal shape) the investigated model returns a deviation of 19.3\% from the experimental values. This motivates a model update by introducing anisotropic conductivity, which is intended to be a simplistic model for heat material convection inside the melt pool. Such an anisotropic model enables the prediction of all quantities of interest mentioned above with a maximum deviation from the experimental values of 6.5\%. We note that, although more predictive, the anisotropic model induces only a marginal increase in computational complexity

The role of FKBP5 in transcriptional regulation and in shaping cellular pathways of psychopharmaca action

FK506 binding protein 5 (FKBP5) has been linked to stress related diseases and treatment response in depression (Binder et al., 2004). The corresponding protein FKBP51 was first identified as co-chaperone of HSP90 in a complex with steroid hormone receptors, where it diminishes hormone affinity and nuclear translocation efficiency of the receptors (Pratt and Toft, 1997; Wochnik et al., 2005). With FKBP5 transcription being induced by glucocorticoid signalling, an ultra-short feedback loop is provided for regulation and termination of GR activity. Dysregulation of this ultra-short feedback loop interferes with the stress hormone regulation and likely contributes to the association of FKBP5 with stress-related psychiatric disorders. Recently, important actions of FKBP51 beyond glucocorticoid signalling have been characterised in shaping the posttranslational regulation of certain molecular pathways in response to treatment with particular psychopharmaca (Gassen et al., 2014, 2015). As a contribution to elucidating the role of FKBP5 in stress related diseases, a two-sided approach was taken in this study by analysing the role of FKBP5 in regulation of transcription and in calibrating the responsiveness of these pathways to psychopharmacological treatment. To elucidate the transcriptional effects of FKBP5 in an unbiased approach, the expression profile of mice with deleted FKBP5 and their litter mates with functional FKBP5 were compared. A marked difference in glyoxalase-1 (GLO1) transcription was observed with higher GLO1 transcription in mice with deleted FKBP5, which was reflected by about two-fold more GLO1 protein in these mice. The efforts in deciphering the role of FKBP5 in elevation of GLO1 expression led to the identification of a duplication of the GLO1 gene inherent to mice with deleted FKBP5; this likely explains the enhanced GLO1 expression in these mice. This observation exemplifies the flanking gene problem and is a note of caution for interpreting data from conventionally generated knock-out mice. Overall, deletion of FKBP5 did not markedly change gene expression. In the second part of this thesis, the molecular effects of psychopharmacologic drugs were profiled for their dependency on FKBP51 function to modulate intracellular pathways relevant for treatment outcome in a cellular FKBP5 knockout model. For this purpose, psychopharmaca from the classes of SSRIs, SSNRIs, TCAs, atypical antidepressants, mood stabilisers, and NMDA receptor antagonists were analysed. In addition to GSK3\ensuremath{β}} and AKT, which were reported to interact with and be targeted by FKBP51 recently (Gassen et al., 2015; Pei et al., 2009), ERK was identified as a novel kinase interacting with and being targeted by FKBP51 in this work. With GSK3{\ensuremath{β}, AKT, and ERK, three major kinases were observed to be regulated by psychopharmaca. The effects were not homogeneous across all psychopharmaca and only loosely followed drug classes. Moreover, regulation of these kinases as well as their downstream targets was non-uniformly influenced by FKBP51. With FKBP51 being a stress induced gene, this transcriptional mechanism efficiently links the stress response to the regulation of the targets analysed in this work. Moreover, markers of autophagy, a cellular degradation process which has been linked to neurotransmission, were detected to be regulated by valproic acid (VPA), a mood stabiliser with HDAC inhibitory activity. VPA, as well as a second HDAC inhibitor butyric acid (BUT) enhanced the transcription of late and delayed autophagy markers controlled by FOXO3 signalling. Considering the versatile action of FKBP51 on targets analysed in this work, the list of proteins modulated by FKBP5 seems by far not complete. The diversity of effects evoked by different psychopharmaca hints to superimposed molecular effects underlying treatment outcome. Better understanding of pathway responsiveness could yield molecular markers for personalised medication that could be utilised to improve treatment outcome in stress related psychiatric diseases

The Small World of Osteocytes: Connectomics of the Lacuno-Canalicular Network in Bone

Osteocytes and their cell processes reside in a large, interconnected network of voids pervading the mineralized bone matrix of most vertebrates. This osteocyte lacuno-canalicular network (OLCN) is believed to play important roles in mechanosensing, mineral homeostasis, and for the mechanical properties of bone. While the extracellular matrix structure of bone is extensively studied on ultrastructural and macroscopic scales, there is a lack of quantitative knowledge on how the cellular network is organized. Using a recently introduced imaging and quantification approach, we analyze the OLCN in different bone types from mouse and sheep that exhibit different degrees of structural organization not only of the cell network but also of the fibrous matrix deposited by the cells. We define a number of robust, quantitative measures that are derived from the theory of complex networks. These measures enable us to gain insights into how efficient the network is organized with regard to intercellular transport and communication. Our analysis shows that the cell network in regularly organized, slow-growing bone tissue from sheep is less connected, but more efficiently organized compared to irregular and fast-growing bone tissue from mice. On the level of statistical topological properties (edges per node, edge length and degree distribution), both network types are indistinguishable, highlighting that despite pronounced differences at the tissue level, the topological architecture of the osteocyte canalicular network at the subcellular level may be independent of species and bone type. Our results suggest a universal mechanism underlying the self-organization of individual cells into a large, interconnected network during bone formation and mineralization