Graz University of Technology
Graz, Austria

The Graz University of Technology is the second largest university in Styria, Austria, after the University of Graz. Austria has three universities of technology – in Graz, in Leoben, and in Vienna. The Graz University of Technology was founded in 1811 by Archduke John of Austria. TU Graz is a public university. In the academic year 2013/14, 15.9% of the students were from abroad and 22.6% of the students were female out of the 12,565 students enrolled at the TU Graz. Wikipedia.

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News Article | May 4, 2017

Light initiates many chemical reactions. Experiments at the Laser Centre of the Institute of Physical Chemistry of the Polish Academy of Sciences and the University of Warsaw's Faculty of Physics have for the first time demonstrated that increasing the intensity of illumination some reactions can be significantly faster. Here, acceleration was achieved using pairs of ultrashort laser pulses. Light-induced reactions can be accelerated by increasing the intensity of illumination -- this has been demonstrated in experiments carried out at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw. In order to thoroughly investigate the nature of the processes involved, ultra-short consecutive pairs of laser pulses were used, and an increase in the rate of reaction between the molecules was observed by up to several dozen percent. The observations of the Warsaw scientists have been reported in the well-known scientific journal Physical Chemistry Chemical Physics. "Our experiments provide fundamental knowledge about the physical processes that are important for the course of important light-induced reactions. This knowledge can potentially be used in many applications, especially when dealing with high intensity light sources. These include, among others, various microscopic imaging techniques, ultra-fast spectroscopy as well as photovoltaics, particularly if light-focusing devices such as solar collectors are used," says Dr. Gonzalo Angulo (IPC PAS). In light-induced reactions, a photon with the appropriate energy excites a molecule of dye. When there is a molecule of quencher near the excited molecule, an interaction takes place: there may be a transfer of energy, an electron or a proton, between the two reactants. Reactions of this type are common in nature. A good example is electron transfer in photosynthesis, which plays a key role in the formation of the Earth's ecosystem. It turns out that a factor that can influence the acceleration of reactions is the intensity of the light that initiates them. In order to study the nature of the processes taking place, the Warsaw chemists used laser pulses lasting femtoseconds instead of the traditional continuous stream of light. The energy of the impulses was adjusted so that, under their influence, the dye molecules moved into the excited energy state. The pulses were grouped in pairs. The interval between pulses in a pair was several dozen picoseconds (trillionths of a second) and was matched to the type of reacting molecules and the environment of the solution. "The theory and the experiments required care and attention, but the physical idea itself is quite simple here," notes Jadwiga Milkiewicz, a PhD student at IPC PAS, and explains: "In order for the reaction to occur, there must be a molecule of quencher near the light-excited dye molecule. So, if we have a pair of molecules that have already reacted with each other this means that they were close enough to each other. By increasing the number of photons in time, we thus increase the chance that if, after the reaction, both molecules have managed to return to their ground state, the absorption of a new photon by the dye has the potential to initiate another reaction before the molecules move away from each other in space." The course of reactions in solutions depends on many factors such as temperature, pressure, viscosity or the presence of an electric or magnetic field. The research at the IPC PAS has proved that these factors also influence the acceleration of the chemical reaction that occurs with an increased intensity of illumination. Under some conditions, the acceleration of the reaction was unnoticeable, in optimal conditions the rate of the reaction increased by up to 25-30%. "In our experiments so far, we have concentrated on light-induced electron transfer reactions, that is, those which change the electrical charge of the molecules. However, we do not see any reason why the mechanism we have observed could not function in other variations of these reactions. So, in the near future, we will try to confirm its efficacy in energy transfer reactions or in reactions involving also proton transfer," says Dr. Angulo. In addition to physicists and chemists from the IPC PAS and the Physics Faculty of the University of Warsaw, financed by the HARMONIA grant of the National Science Centre, a group headed by Prof. Gunther Grampp from Graz University of Technology participated in the experiments. In the Austrian laboratory, comparative experiments were carried out on samples illuminated in a continuous manner. Also involved in the team's theoretical work was Dr. Daniel Kattnig from the University of Oxford. This press release was prepared with funds from the European ERA Chairs grant under the Horizon 2020 programme. The Institute of Physical Chemistry of the Polish Academy of Sciences was established in 1955 as one of the first chemical institutes of the PAS. The Institute's scientific profile is strongly related to the newest global trends in the development of physical chemistry and chemical physics. Scientific research is conducted in nine scientific departments. CHEMIPAN R&D Laboratories, operating as part of the Institute, implement, produce and commercialise specialist chemicals to be used, in particular, in agriculture and pharmaceutical industry. The Institute publishes approximately 200 original research papers annually.

Ruckert E.,Graz University of Technology | d'Avella A.,Laboratory of Neuromotor Physiology
Frontiers in Computational Neuroscience | Year: 2013

A salient feature of human motor skill learning is the ability to exploit similarities across related tasks. In biological motor control, it has been hypothesized that muscle synergies, coherent activations of groups of muscles, allow for exploiting shared knowledge. Recent studies have shown that a rich set of complex motor skills can be generated by a combination of a small number of muscle synergies. In robotics, dynamic movement primitives are commonly used for motor skill learning. This machine learning approach implements a stable attractor system that facilitates learning and it can be used in high-dimensional continuous spaces. However, it does not allow for reusing shared knowledge, i.e., for each task an individual set of parameters has to be learned. We propose a novel movement primitive representation that employs parametrized basis functions, which combines the benefits of muscle synergies and dynamic movement primitives. For each task a superposition of synergies modulates a stable attractor system. This approach leads to a compact representation of multiple motor skills and at the same time enables efficient learning in high-dimensional continuous systems. The movement representation supports discrete and rhythmic movements and in particular includes the dynamic movement primitive approach as a special case. We demonstrate the feasibility of the movement representation in three multi-task learning simulated scenarios. First, the characteristics of the proposed representation are illustrated in a point-mass task. Second, in complex humanoid walking experiments, multiple walking patterns with different step heights are learned robustly and efficiently. Finally, in a multi-directional reaching task simulated with a musculoskeletal model of the human arm, we show how the proposed movement primitives can be used to learn appropriate muscle excitation patterns and to generalize effectively to new reaching skills. © 2013 Rückert and d'Avella.

News Article | December 15, 2016

The porous crystals known as metal-organic frameworks (MOFs) consist of metallic intersections connected by organic molecules. Thanks to their high porosity, MOFs have an extremely large surface area: a teaspoonful of MOF has the same surface area as a football pitch. The large number of pores situated in an extremely small space offer room for ‘guests’, allowing MOFS to be used for gas storage or as a ‘molecular gate’ for separating chemicals. But MOFs have a much greater potential, and this is what Paolo Falcaro from the Institute of Physical and Theoretical Chemistry (PTC) at the Graz University of Technology (TU Graz) in Austria wants to unlock. “MOFs are prepared by self-organization,” Falcaro explains. “We don’t have to do anything other than mix the components, and the crystals will grow by themselves. However, crystals grow with random orientation and position, and thus their pores. Now, we can control this growth, and new properties of MOFs will be explored for multifunctional use in microelectronics, optics, sensors and biotechnology.” In a paper in Nature Materials, Falcaro and his team report a method for growing MOFs on a comparatively large surface area of 1cm2 that offers an unprecedented level of control over the orientation and alignment of the crystals. Other members of the team include Masahide Takahashi from Osaka Prefecture University in Japan and researchers from the University of Adelaide, Monash University and the Commonwealth Scientific and Industrial Research Organisation (CSIRO), all in Australia. Incorporating functional materials into these precisely-oriented crystals allows the creation of anisotropic materials, which are materials with directionally-dependent properties. In the paper, the research team describes incorporating fluorescent molecules into a precisely-oriented MOF. Just by rotating the film, the fluorescent signal can be turned ‘on’ or ‘off’, producing an optically-active switch. “This has many conceivable applications and we’re going to try many of them with a variety of different functionalities,” says Falcaro. “One and the same material can show different properties through different orientations and alignments. Intentional growth of MOFs on this scale opens up a whole range of promising applications which we’re going to explore step by step.” A major aim of Falcaro and his team at TU Graz is developing MOFs for biotechnological applications. “We are trying to encapsulate enzymes, proteins and even DNA in MOFs and to immunize their activity against fluctuations in temperature,” he says. “The crystalline structure surrounding the ‘guest’ in the pore has a protective effect, like a tough jacket. We want to check out the possibilities more accurately.” This story is adapted from material from TU Graz, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

Bill J.,Graz University of Technology | Legenstein R.,Graz University of Technology
Frontiers in Neuroscience | Year: 2014

Memristors have recently emerged as promising circuit elements to mimic the function of biological synapses in neuromorphic computing. The fabrication of reliable nanoscale memristive synapses, that feature continuous conductance changes based on the timing of pre- and postsynaptic spikes, has however turned out to be challenging. In this article, we propose an alternative approach, the compound memristive synapse, that circumvents this problem by the use of memristors with binary memristive states. A compound memristive synapse employs multiple bistable memristors in parallel to jointly form one synapse, thereby providing a spectrum of synaptic efficacies. We investigate the computational implications of synaptic plasticity in the compound synapse by integrating the recently observed phenomenon of stochastic filament formation into an abstract model of stochastic switching. Using this abstract model, we first show how standard pulsing schemes give rise to spike-timing dependent plasticity (STDP) with a stabilizing weight dependence in compound synapses. In a next step, we study unsupervised learning with compound synapses in networks of spiking neurons organized in a winner-take-all architecture. Our theoretical analysis reveals that compound-synapse STDP implements generalized Expectation-Maximization in the spiking network. Specifically, the emergent synapse configuration represents the most salient features of the input distribution in a Mixture-of-Gaussians generative model. Furthermore, the network's spike response to spiking input streams approximates a well-defined Bayesian posterior distribution. We show in computer simulations how such networks learn to represent high-dimensional distributions over images of handwritten digits with high fidelity even in presence of substantial device variations and under severe noise conditions. Therefore, the compound memristive synapse may provide a synaptic design principle for future neuromorphic architectures. © 2014 Bill and Legenstein.

Pock T.,Graz University of Technology | Chambolle A.,French National Center for Scientific Research
Proceedings of the IEEE International Conference on Computer Vision | Year: 2011

In this paper we study preconditioning techniques for the first-order primal-dual algorithm proposed in [5]. In particular, we propose simple and easy to compute diagonal preconditioners for which convergence of the algorithm is guaranteed without the need to compute any step size parameters. As a by-product, we show that for a certain instance of the preconditioning, the proposed algorithm is equivalent to the old and widely unknown alternating step method for monotropic programming [7]. We show numerical results on general linear programming problems and a few standard computer vision problems. In all examples, the preconditioned algorithm significantly outperforms the algorithm of [5]. © 2011 IEEE.

Wieser B.,Graz University of Technology
Social Science and Medicine | Year: 2010

A number of European countries have expanded their screening programme considerably during the last decade. Other countries have, however, not expanded their programme substantially. In this paper, I will compare UK and Austria, two countries representing two ends of the European spectrum. Focussing on the decision-making processes behind the design and expansion of newborn screening, I draw on Sheila Jasanoff's concept of " civic epistemology"(Jasanoff, S. (2005). Designs on Nature. Princeton and Oxford: Princeton University Press.) to investigate how the chosen countries provide information in order to give account for their respective screening policies. In particular, I analyse how key institutions in the UK and Austria use scientific expertise to explain and justify national screening programmes. For this purpose, I compare the material that is made available to the public, including policy documents, scientific studies, medical guidelines, legal regulation, advisory committee reports and public engagement exercises. It was found that the observed differences in the accountability practices are rooted in nationally traditional forms of policy making. However, whether or not these repertoires become indeed realised is a more contingent matter and is often triggered by events which evoke a response from the medical and policy-making actors. © 2010 Elsevier Ltd.

Donoser M.,Graz University of Technology | Bischof H.,Graz University of Technology
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2013

In this paper we revisit diffusion processes on affinity graphs for capturing the intrinsic manifold structure defined by pair wise affinity matrices. Such diffusion processes have already proved the ability to significantly improve subsequent applications like retrieval. We give a thorough overview of the state-of-the-art in this field and discuss obvious similarities and differences. Based on our observations, we are then able to derive a generic framework for diffusion processes in the scope of retrieval applications, where the related work represents specific instances of our generic formulation. We evaluate our framework on several retrieval tasks and are able to derive algorithms that e., g. a 100% bulls eye score on the popular MPEG7 shape retrieval data set. © 2013 IEEE.

Wriessnegger T.,Acib Austrian Center of Industrial Biotechnology | Pichler H.,Acib Austrian Center of Industrial Biotechnology | Pichler H.,Graz University of Technology
Progress in Lipid Research | Year: 2013

Terpenoids comprise various structures conferring versatile functions to eukaryotes, for example in the form of prenyl-anchors they attach proteins to membranes. The physiology of eukaryotic membranes is fine-tuned by another terpenoid class, namely sterols. Evidence is accumulating that numerous membrane proteins require specific sterol structural features for function. Moreover, sterols are intermediates in the synthesis of steroids serving as hormones in higher eukaryotes. Like steroids many compounds of the terpenoid family do not contribute to membrane architecture, but serve as signalling, protective or attractant/repellent molecules. Particularly plants have developed a plenitude of terpenoid biosynthetic routes branching off early in the sterol biosynthesis pathway and, thereby, forming one of the largest groups of naturally occurring organic compounds. Many of these aromatic and volatile molecules are interesting for industrial application ranging from foods to pharmaceuticals. Combining the fortunate situation that sterol biosynthesis is highly conserved in eukaryotes with the amenability of yeasts to genetic and metabolic engineering, basically all naturally occurring terpenoids might be produced involving yeasts. Such engineered yeasts are useful for the study of biological functions and molecular interactions of terpenoids as well as for the large-scale production of high-value compounds, which are unavailable in sufficient amounts from natural sources due to their low abundance. © 2013 Elsevier Ltd. All rights reserved.

Morandi O.,Graz University of Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The femtosecond laser excitation of the spin configuration in a low-dimensional magnetic semiconductor is investigated. An atomistic Schrödinger model is developed in which trapped electrons and ionic impurities are coupled via exchange interactions. By defining a suitable set of non-Hermitian operators, the microscopic Schrödinger description of the particles is combined with the more phenomenological Landau-Bloch relaxation mechanism. Differing from the standard approaches, in this model the statistical widths of the wave functions become time-dependent. This enables the study of decoherence effects where the evolution of the system, from an initial pure state to a final mixed state, is induced by the spin interaction. Simulations reproduce the out-of-equilibrium spin evolution observed in ZnCdSe devices. The effects of quantum confinement and multimode excitation are discussed. © 2011 American Physical Society.

Lehner F.,Graz University of Technology
Journal of Combinatorial Theory. Series B | Year: 2014

We prove a refinement of the tree packing theorem by Tutte/Nash-Williams for finite graphs. This result is used to obtain a similar result for end faithful spanning tree packings in certain infinite graphs and consequently to establish a sufficient Hamiltonicity condition for the line graphs of such graphs. © 2014 Elsevier Inc.

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