IST Austria: PubRep (Institute of Science and Technology)
Not a member yet
6140 research outputs found
Sort by
Stopping criteria for value iteration on concurrent stochastic reachability and safety games
No full textWe consider two-player zero-sum concurrent stochastic games (CSGs) played on graphs with reachability and safety objectives. These include degenerate classes such as Markov decision processes or turn-based stochastic games, which can be solved by linear or quadratic programming; however, in practice, value iteration (VI) outperforms the other approaches and is the most implemented method. Similarly, for CSGs, this practical performance makes VI an attractive alternative to the standard theoretical solution via the existential theory of reals.VI starts with an under-approximation of the sought values for each state and iteratively updates them, traditionally terminating once two consecutive approximations are ϵ-close. However, this stopping criterion lacks guarantees on the precision of the approximation, which is the goal of this work. We provide bounded (a.k.a. interval) VI for CSGs: it complements standard VI with a converging sequence of over-approximations and terminates once the over- and under-approximations are ϵ-close
Photochemical cross-couplings using semiconducting materials
No full textIn this personal account, I describe the work performed in my research group on the development of methods that harness heterogeneous photocatalysts for light-mediated nickel-catalyzed cross-couplings. This includes catalytic systems using carbon nitride materials, dye-sensitized TiO₂, covalent organic frameworks (COFs), and conjugated polymers. The rationale behind the selection of materials and how their use led to the identification of catalyst deactivation, structure–activity relationships, and future opportunities is discussed
Beyond the Nyquist frequency
No full textSubgiants and early red giants are crucial for studying the first dredge-up, a key evolutionary phase in which the convective envelope deepens, mixing previously interior-processed material and bringing it to the surface. Yet, very few have been seismically characterized with Kepler because their oscillation frequencies are close to the 30 minute sampling frequency of the mission. We developed a new method as part of the new PyA2Z code of identifying super-Nyquist oscillators and inferring their global seismic parameters, νmax and large separation, Δν.
Applying PyA2Z to 2065 Kepler targets, we seismically characterize 285 super-Nyquist and 168 close-to-Nyquist stars with masses from 0.8 to 1.6 M⊙. In combination with APOGEE spectroscopy, Gaia spectrophotometry, and stellar models, we derive stellar ages for the sample. There is good agreement between the predicted and actual positions of stars on the HR diagram (luminosity vs. effective temperature) as a function of mass and composition. While the timing of dredge-up is consistent with predictions, the magnitude and mass dependence show discrepancies with models, possibly due to uncertainties in model physics or calibration issues in observed abundance scales
Surpassing the loss-noise robustness trade-off in quantum key distribution
No full textQuantum key distribution (QKD) offers a theoretically secure method to share secret keys, yet practical implementations face challenges due to noise and loss over long-distance channels. Traditional QKD protocols require extensive noise compensation, hindering their industrial scalability and lowering the achievable key rates. Alternative protocols encode logical qubits in noise-resilient states but at the cost of using many physical qubits, increasing susceptibility to loss and limiting transmission distance. In this work, we introduce a logical-qubit encoding that uses antisymmetric Bell states in the continuous photonic degrees of freedom, frequency and time. By leveraging the continuous space, we overcome this noise-loss robustness trade-off by minimizing the number of photons per logical qubit while optimizing the encoding resilience over noise fluctuations. We analyze the security of our encoding and demonstrate its robustness compared to existing state-of-the-art protocols. This approach provides a path toward scalable, efficient QKD implementations under realistic noise conditions
Cavity based sensing of antiferromagnetic canting and nonzero-momentum spin waves in a van der Waals cavity-magnon-polariton system
No full textCavity-magnon polaritons are hybrid excitations from the interaction between cavity photons and magnons, the quanta of collective spin oscillations. Along with the tunability of the magnon-photon coupling strength, fast information transfer and conversion speed are desired in hybrid devices. This can be achieved utilizing the propagating nature of spin waves with nonzero momentum for their ultrafast time dynamics and reduced ohmic dissipation. Antiferromagnets are particularly interesting as hosts for magnons since stray-field interactions are minimized and they support multiple modes with distinctive magnetic-field behavior across the phase diagram. Chromium trichloride (CrCl3) is a van der Waals layered antiferromagnet having a strong easy-plane anisotropy and a weak in-plane easy-axis anisotropy. Despite some magnetic resonance studies, the impact of magnetic reorientation of spins in CrCl3 on the cavity-magnon-polariton interaction strength as a function of magnetic field remains largely unexplored. In this study, we investigate the coupling between magnons in CrCl3 and photons in a coplanar waveguide resonator as a function of magnetic field. In particular, we find that the magnon-photon coupling strength varies nonmonotonically and distinctly with the magnetic field for the acoustic and the optical magnons, which can be utilized to tune the magnon-photon coupling strength using an external magnetic field as a knob. We find the signature of spin-flop transition in the two harmonics of the cavity due to a stronger dispersive coupling between optical magnons and cavity photons at lower fields. Additionally, we find standing modes formed by spin waves with nonzero momentum associated with the two hybrid magnons when the external field is applied at an angle with the crystal plane. These modes do not undergo substantial coupling with the cavity mode unlike the antiferromagnetic modes and can be used as low-loss propagation channels in hybrid devices
Essentials of transcriptomic methods: Navigating through RNA sequencing and beyond
No full textRNA sequencing (RNA-seq) methodologies have evolved rapidly, offering powerful tools to study gene expression, transcriptome dynamics, and molecular mechanisms in various biological contexts. However, the complexity of these approaches poses challenges in data interpretation, sensitivity, and applicability. This chapter provides a comprehensive overview of RNA-seq methodologies, highlighting their advantages, limitations, and applications, particularly in cardiovascular research. Bulk RNA sequencing enables high-throughput gene expression profiling but lacks the resolution to capture cellular heterogeneity and spatial context. Direct RNA sequencing preserves native RNA modifications, offering insights into post-transcriptional regulation, though it remains technically challenging. Single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) bridge these gaps by resolving transcriptomic complexity at the cellular level and within tissue architecture, providing crucial insights into disease mechanisms such as atherosclerosis. By summarizing the strengths and limitations of these methodologies, this chapter aims to guide researchers in selecting the most suitable transcriptomic approach for their studies, ultimately advancing precision medicine and biomarker discovery in cardiovascular disease
TXNIP mediates LAT1/SLC7A5 endocytosis to limit amino acid uptake in cells entering quiescence
No full textEntry into and exit from cellular quiescence require dynamic adjustments in nutrient acquisition, yet the mechanisms by which quiescent cells downregulate amino acid (AA) transport remain poorly understood. Here we show that cells entering quiescence selectively target plasma membrane-resident amino acid transporters for endocytosis and lysosomal degradation. This process matches amino acid uptake with reduced translational demand and promotes survival during extended periods of quiescence. Mechanistically, we identify the α-arrestin TXNIP as a key regulator of this metabolic adaptation, since it mediates the endocytosis of the SLC7A5-SLC3A2 (LAT1-4F2hc) AA transporter complex in response to reduced AKT signaling. To promote transporter ubiquitination, TXNIP interacts with NEDD4L and other HECT-type ubiquitin ligases. Loss of TXNIP disrupts this regulation, resulting in dysregulated amino acid uptake, sustained mTORC1 signaling, and ultimately cell death under prolonged quiescence. The characterization of a novel TXNIP loss-of-function variant in a patient with a severe metabolic disease further supports its role in nutrient homeostasis and human health. Together, these findings highlight TXNIP’s central role in controlling nutrient acquisition and metabolic plasticity with implications for quiescence biology and diseases
The role of institutional ethics committees in Austria: Report of the Commission on Ethics and Scientific Integrity of the Karl Landsteiner University of Health Sciences 2018–2023
No full textResearch involving human subjects or identifiable human material and data must be assessed by an ethics committee. The Karl Landsteiner University of Health Sciences has established a Commission on Ethics and Scientific Integrity to evaluate medical research conducted by its faculty and students and at its affiliated hospitals.
All projects submitted to the Commission on Ethics and Scientific Integrity between 2018 and 2023 were analyzed regarding their major characteristics, the duration of the evaluation process, and votes issued.
A total of 520 applications were electronically submitted during the observation period. Most of the studies were retrospective data analyses in the field of oncology, psychology and surgery. Most studies included less than 100 volunteers. Of the applications 50% received a final vote within 5 months, during which several revision rounds took place. Overall, about 77% of votes issued during the observation period were positive and 2% were rejections. In 11% files were closed due to withdrawal. In 11% final votes were pending at the end of the observation period due to requests for revisions.
Our results emphasize the importance of institutional ethics committees using the example of the Commission on Ethics and Scientific Integrity at the Karl Landsteiner University. Such committees fill a gap in evaluating research not covered by Austrian legal regulations. Continuous development of standards, operating procedures, and national and international collaborations are required to assess and minimize risks to trial subjects and to provide a safe and productive environment for research in human medicine and related fields
ISTA Thesis
No full textRotations are found in physics problems at all scales: from spatial motion of celestial bodies, to transitions between quantum states of atoms and molecules. Mathematically, they represent a fundamental class of transformations and symmetries. Unlike spatial displacements, rotational transformations in three-dimensional space are non-commutative: the result of applying a sequence of rotations depends on the order of these operations. This feature makes the emergent physics that involves rotations rather intricate, but instrumental for studies of highly-interconnected many-body systems. In the presence of an environment, rotational properties of an object change, due to the interaction with particles of the environment. Owing to the complexity of this interaction, it can be engineered to exhibit certain properties of interest. In this Thesis, we examine several scenarios of how the rotational behavior of an impurity can be modified by interactions with its environment
Constraining differential rotation in γ Doradus stars from the properties of inertial dips
No full textContext. The presence of dips in the gravity mode period spacing versus period diagram of γ Doradus stars is now well established thanks to recent asteroseismic studies. Such Lorentzian-shaped inertial dips arise from the interaction of gravito-inertial modes in the radiative envelope of intermediate-mass main sequence stars with pure inertial modes in their convective core, and allow us to study stellar internal properties. This window onto stellar internal dynamics is extremely valuable in the context of the understanding of angular-momentum transport inside stars, as it allows us to probe rotation in their core.
Aims. We investigate the signature and the detectability of a differential rotation between the convective core and the near-core region inside γ Doradus stars from the properties of inertial dips.
Methods. We studied the coupling between gravito-inertial modes in the radiative zone and pure inertial modes in the convective core in the sub-inertial regime, allowing for a two-zone differential rotation from the two sides of the core-to-envelope boundary. We solved the coupling equation numerically and matched the result to an analytical derivation of the Lorentzian dip properties. We then used typical values of measured near-core rotation and buoyancy travel time to infer ranges of parameters for which differential core to near-core rotation would be detectable in current Kepler data.
Results. We show that increasing the convective core rotation with respect to the near-core rotation leads to a shift of the period of the observed dip to lower periods. In addition, the dip gets deeper and thinner as the convective core rotation increases. We demonstrate that such a signature is detectable in Kepler data, given appropriate dip-parameter ranges and near-core structural properties.
Conclusions. Studying the dip properties in asteroseismic data thus allows us to access core to near-core radial differential rotation and to better understand the transport of angular momentum at convective–radiative interfaces in intermediate-mass main sequence stars