Investigations regarding the pumping process of wet-mix shotcrete improvement and upgrading of underground traffic structures

Workability is a physical property of fresh concrete, which can’t be described with only one single parameter or measured with one single test method. Pumpability and sprayability plays an important role for wet-mix sprayed concrete. The material must be conveyed through the pipe without changing its properties and mix proportion. The mix should leave the nozzle in a uniform stream intermixed homogeneously with the accelerator. When concrete is pumped through a pipe, a thin layer of paste is lubricating the wall of the pipe. The interaction of the lubricating layer and the pipe wall is of great importance for pumpability. The shear of the layer allows the slipping of the concrete and leads to a reduction of the required pumping pressure. In this presentation a sliding pipe rheometer “Sliper” is used to determine the pumping capacity of concrete. The Sliper consists of a pipe and a guided piston which is standing on the ground. A pressure sensor is integrated onto the piston. When the pipe is sliding downwards, the pressure in the pipe as well as the speed of the pipe are recorded. Rheological parameters as well as the supposed pumping pressure may be estimated. The cohesiveness of concrete is important to avoid blockages in the conveying pipe. Blockages can occur, when the paste separates from the aggregate skeleton because of a high pressure in the pipe. The stability of the wet-mix was determined by a filter pressing test. Mixes tested by the Sliper and the filter press were then sprayed with a wet-mix shotcrete machine Sika PM 500. This machine was equipped with seven pressure sensors, which could monitor the pressure over time. The sensors measured the pressure of the hydraulic system, the mix at the beginning and end of the pumping line, the pressure of the accelerator shortly after the pump and at the end of the hose, the pressure of the air and finally the pressure in the aerosol converter. Simultaneously, the spraying was filmed by a high-speed camera. This slow-motion recording shows the homogeneity and pulsation of the spray jet. At its best, shotcrete should emerge from the nozzle in a steady, uninterrupted flow. Different durable and sustainable mixes, developed under the Austrian research project ASSpC, were sprayed at different output of the shotcrete machine. The results and lessons learned from the results will be final part of the presentation

Effect of second order piezoelectricity on excitonic structure of stress-tuned InGaAs/GaAs quantum dots

We study the effects of the nonlinear piezoelectricity and the In distribution on the exciton energy, the electron-hole electric dipole moment, and the fine-structure splitting in stress-tunable InGaAs/GaAs quantum dots integrated onto a piezoelectric actuator. In particular, we investigate in detail the contributions of various elements of the expansion of the electrical polarization in terms of externally induced elastic strain on the latter two important quantum dot properties. Based on the comparison of the effects of first- and second-order piezoelectricity we provide a simple relation to estimate the influence of applied anisotropic stress on the quantum dot dipole moment for quantum dots significantly lattice mismatched to the host crystal

Sarcopenia in Neurological Patients: Standard Values for Temporal Muscle Thickness and Muscle Strength Evaluation.

Temporal muscle thickness (TMT) was investigated as a novel surrogate marker on MRI examinations of the brain, to detect patients who may be at risk for sarcopenia. TMT was analyzed in a retrospective, normal collective cohort (n = 624), to establish standard reference values. These reference values were correlated with grip strength measurements and body mass index (BMI) in 422 healthy volunteers and validated in a prospective cohort (n = 130) of patients with various neurological disorders. Pearson correlation revealed a strong association between TMT and grip strength (retrospective cohort, ρ = 0.746; p < 0.001; prospective cohort, ρ = 0.649; p < 0.001). A low or no association was found between TMT and age (retrospective cohort, R2 correlation coefficient 0.20; p < 0.001; prospective cohort, ρ = -0.199; p = 0.023), or BMI (retrospective cohort, ρ = 0.116; p = 0.042; prospective cohort, ρ = 0.227; p = 0.009), respectively. Male patients with temporal wasting and unintended weight loss, respectively, showed significantly lower TMT values (p = 0.04 and p = 0.015, unpaired t-test). TMT showed a high correlation with muscle strength in healthy individuals and in patients with various neurological disorders. Therefore, TMT should be integrated into the diagnostic workup of neurological patients, to prevent, delay, or treat sarcopenia

Mechanism of KMT5B haploinsufficiency in neurodevelopment in humans and mice.

Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest (n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems

Neue Monomere für zähe Photopolymere

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersPhotopolymere stellen eine weitverbreitete Materialklasse dar und werden für eine Vielzahl an Anwendungen von Tinten und Beschichtungen, aber auch für medizinische Materialien und Additive Manufacturing (3D Druck) eingesetzt. Der Mangel an Zähigkeit verhindert jedoch nach wie vor eine breitere Verwendung in der Industrie. Um diese Nachteile zu überwinden, wurden in der Literatur bereits einige vielversprechende Konzepte veröffentlicht (z.B. Additive oder Modifizierung der Polymerstruktur). Diese Ansätze bringen aber andere Nachteile einher, wie hohe Viskosität, Verschlechterung verschiedener anderer (thermo)mechanischer Eigenschaften im Austausch für eine hohe Zähigkeit oder sind einfach zu teuer für viele Anwendungen.Daher war das Ziel dieser Arbeit, neue Ansätze zur Verringerung der Sprödigkeit in Photopolymeren zu finden. Dazu wurden zwei unterschiedliche Konzepte verfolgt und im Detail – beginnend bei Formulierungseigenschaften bis hin zu (thermo)mechanischen Eigenschaften des fertigen Materials – untersucht.Einerseits wurden neue vernetzende Monomere mit geblockten Isocyanaten hergestellt, die thermisch gespalten werden können. Dadurch gelang es, die Netzwerkarchitektur von einem stark vernetzten hin zu einem linearen thermoplastischen Polymer zu verändern.Andererseits wurde ein Konzept entwickelt, welches ABS als bekannten und zähen Kunststoff zum Vorbild nahm. Da ABS nicht photopolymerisiert werden kann, wurden neue Terpolymere basierend auf Maleimid, Styrol und Polybutadien entwickelt, um die Struktur und Eigenschaften von ABS nachzuahmen. Darüber hinaus wurden weitere Monomere synthetisiert, um verschiedene Monomer- und Materialeigenschaften zu optimieren und ein besseres Verständnis für diese neuartigen transparenten ABS-ähnlichen Photopolymere zu entwickeln. Schlussendlich konnten drei mögliche Anwendungen (Reaktivverdünner für kommerzielle hochviskose Harze, Frontalpolymerisation und 3D Druck) aufgezeigt werden, welche den Weg für diese neue vielversprechende Photopolymerklasse ebnen können.Photopolymers are a widely spread class of materials. They are utilised in thin layer applications such as inks and protective and decorative coatings to more sophisticated uses like medical applications or additive manufacturing technologies. Nevertheless, lack of toughness still limits utilisation of bulk materials in industry. For this purpose, several promising concepts were already published in literature to overcome these drawbacks (e.g. toughening additives or modification of the polymer network). However, they exhibit other disadvantages such as high viscosity, decrease of other (thermo)mechanical properties in exchange for toughness or are quite simply too expensive for many areas.Therefore, the aim of this thesis was to investigate new approaches to tackle brittleness in photopolymers. Thus, two different independent plans were pursued and studied in detail ranging from resin characterisation to determination of (thermo)mechanical properties of the final materials.On the one hand, new cross-linking monomers were synthesised containing blocked isocyanates, which could be cleaved thermally. So, a change in network architecture from highly cross-linked to linear thermoplastic polymers was achieved.On the other hand, a concept was developed, which was modelled on ABS as a very prominent and tough engineering plastic. Unfortunately, ABS cannot be photopolymerised. Thus, new terpolymers based on maleimide, styrene and polybutadiene were explored to mimic structure and properties of ABS. Furthermore, additional derivatives were synthesised to optimise monomer and material characteristics and to acquire a deeper understanding of these novel transparent ABS-like photopolymers. Finally, three different potential applications were shown (reactive diluent for commercial highly viscous resins, frontal polymerisation and 3D printing), which could pave the way for this new promising photopolymer class in research and industry.22

Limit cycles at oversteer vehicle

Handling and stability properties of automobiles are most often studied from a practical point of view by applying a reduced set of equations, where the forward velocity is kept constant. At studying the full set of equations of a basic nonlinear two-wheel vehicle model, a supercritical Hopf bifurcation is found for an oversteer vehicle. All state variables of the vehicle are involved at small amplitude limit cycles in the vicinity of the Hopf bifurcation point with the steering angle (drive torque) as bifurcation parameter. At the transition to large amplitude relaxation cycles, the cyclic motion of the vehicle may be separated into ‘slow’ longitudinal velocity-related segments, and ‘fast’ vehicle yaw and side slip-related segments, indicating a singular perturbed system. Moreover, Canard phenomenon is observed for both steering angle and drive torque bifurcation parameters

Microstructural PALS study of regulated dimethacrylates: Thiol- versus β-allyl sulfone-based networks

The final publication is available via https://doi.org/10.1002/polb.24240.Radical photocuring of multifunctional (meth)acrylates is lacking control over the irregular chain growth process yielding highly crosslinked, inhomogeneous networks. Chain transfer agents (CTAs, e.g. thiols or β-allyl sulfones) have been widely used to modify this curing process, thus reducing shrinkage stress and increasing the toughness of the formed photopolymers. Resulting photopolymer networks exhibit higher bulk density, lower crosslinking density and narrow glass transitions. Consequently, a more homogeneous network structure was postulated for those networks. Whereas macroscopic properties of the modified final materials have already been studied, herein the microstructural arrangement of such modified networks has also been evaluated with the help of positron annihilation lifetime spectroscopy (PALS). A more homogenous network structure with a decreased free-volume void size was confirmed for CTA-based dimethacrylate networks. A sharper distribution of the orthopositronium (o-Ps) lifetime, mainly for the β-allyl sulfone-based photopolymers, hints towards a more regulated network structure. Moreover, the combination of PALS, DMTA, density and swelling experiments elucidates relations between void formation, crosslinking density and macroscopic characteristics such as shrinkage stress and mechanical properties.Austrian Science Funds (FWF

Light-triggered radical silane-ene chemistry using a monoalkyl substituted bis(trimethylsilyl)silane

The final publication is available via https://doi.org/10.1002/macp.201600563.Chain transfer agents (e.g., thiols) enrich radical photopolymerization for use in advanced applications such as stereolithography, optical materials, and biomedicine. Resulting thiolene-based photopolymers exhibit numerous benefits such as tunable thermomechanical properties, and give access to spatially resolved functional materials. Silane-ene chemistry could serve as alternative to this popular thiol-ene approach. A monosubstituted bis(trimethylsilyl)silane (MSiH) is synthesized by a simple one pot procedure. Photoinitiated radical silane-ene chemistry has been performed with multiple enes and the conversions are assessed by 1H NMR spectroscopy. Compared to the most reactive silane from literature, tris(trimethylsilyl)silane (TTMSSiH), the radical reactivity of MSiH is reduced in all tested formulations, but the possibility for further functionalization and accessibility of multifunctional MSiH-derivatives is upheld. A silane-acrylate formulation is found to be most promising. In comparison to a thiolacrylate system, a more uniform conversion of the chain transfer agent and acrylate is shown for the silaneacrylate formulation with MSiH. The promising results for the silane-acrylate system are confirmed by further tests (i.e., NMR spectroscopy, GPC, and MALDI MS), giving additional information on molecular weight regulation and radical mechanism. First MSiH-based photopolymer networks have been fabricated and analyzed via DMTA, thus paving the way for future silane-acrylate networks.Austrian Science Funds (FWF