118 research outputs found
Frenet-Cartesian Model Representations for Automotive Obstacle Avoidance within Nonlinear MPC
In recent years, nonlinear model predictive control (NMPC) has been
extensively used for solving automotive motion control and planning tasks. In
order to formulate the NMPC problem, different coordinate systems can be used
with different advantages. We propose and compare formulations for the NMPC
related optimization problem, involving a Cartesian and a Frenet coordinate
frame (CCF/ FCF) in a single nonlinear program (NLP). We specify costs and
collision avoidance constraints in the more advantageous coordinate frame,
derive appropriate formulations and compare different obstacle constraints.
With this approach, we exploit the simpler formulation of opponent vehicle
constraints in the CCF, as well as road aligned costs and constraints related
to the FCF. Comparisons to other approaches in a simulation framework highlight
the advantages of the proposed approaches
Increased expression of 5-hydroxytryptamine(2A/B) receptors in idiopathic pulmonary fibrosis: a rationale for therapeutic intervention
Background
Idiopathic pulmonary fibrosis (IPF) has a poor prognosis and limited responsiveness to available treatments. It is characterised by epithelial cell injury, fibroblast activation and proliferation and extracellular matrix deposition. Serotonin (5-hydroxytryptamine; 5-HT) induces fibroblast proliferation via the 5-HTR2A and 5-HTR2B receptors, but its pathophysiological role in IPF remains unclear. A study was undertaken to determine the expression of 5-HT receptors in IPF and experimental lung fibrosis and to investigate the effects of therapeutic inhibition of 5-HTR2A/B signalling on lung fibrosis in vivo and in vitro.
Methods and results
Quantitative RT-PCR showed that the expression of 5-HTR1A/B and 5-HTR2B was significantly increased in the lungs of patients with IPF (n = 12) and in those with non-specific interstitial pneumonia (NSIP, n = 6) compared with transplant donors (n = 12). The expression of 5-HTR2A was increased specifically in IPF lungs but not in NSIP lungs. While 5-HTR2A protein largely localised to fibroblasts, 5-HTR2B localised to the epithelium. To assess the effects of 5HTR(2A/B) inhibition on fibrogenesis in vivo, mice were subjected to bleomycin-induced lung fibrosis and treated with the 5-HTR2A/B antagonist terguride (or vehicle) in a therapeutic approach (days 14-28 after bleomycin). Terguride-treated mice had significantly improved lung function and histology and decreased collagen content compared with vehicle-treated mice. Functional in vitro studies showed that terguride is a potent inhibitor of transforming growth factor beta(1)- or WNT3a-induced collagen production.
Conclusion
The studies revealed an increased expression of 5-HTR2A specifically in IPF. Blockade of 5-HTR2A/B signalling by terguride reversed lung fibrosis and is thus a promising therapeutic approach for IPF
An Inverse Optimal Control Approach for Trajectory Prediction of Autonomous Race Cars
This paper proposes an optimization-based approach to predict trajectories of
autonomous race cars. We assume that the observed trajectory is the result of
an optimization problem that trades off path progress against acceleration and
jerk smoothness, and which is restricted by constraints. The algorithm predicts
a trajectory by solving a parameterized nonlinear program (NLP) which contains
path progress and smoothness in cost terms. By observing the actual motion of a
vehicle, the parameters of prediction are updated by means of solving an
inverse optimal control problem that contains the parameters of the predicting
NLP as optimization variables. The algorithm therefore learns to predict the
observed vehicle trajectory in a least-squares relation to measurement data and
to the presumed structure of the predicting NLP. This work contributes with an
algorithm that allows for accurate and interpretable predictions with sparse
data. The algorithm is implemented on embedded hardware in an autonomous
real-world race car that is competing in the challenge Roborace and analyzed
with respect to recorded data.Comment: ECC 202
Safe Imitation Learning of Nonlinear Model Predictive Control for Flexible Robots
Flexible robots may overcome some of the industry's major challenges, such as
enabling intrinsically safe human-robot collaboration and achieving a higher
load-to-mass ratio. However, controlling flexible robots is complicated due to
their complex dynamics, which include oscillatory behavior and a
high-dimensional state space. NMPC offers an effective means to control such
robots, but its extensive computational demands often limit its application in
real-time scenarios. To enable fast control of flexible robots, we propose a
framework for a safe approximation of NMPC using imitation learning and a
predictive safety filter. Our framework significantly reduces computation time
while incurring a slight loss in performance. Compared to NMPC, our framework
shows more than a eightfold improvement in computation time when controlling a
three-dimensional flexible robot arm in simulation, all while guaranteeing
safety constraints. Notably, our approach outperforms conventional
reinforcement learning methods. The development of fast and safe approximate
NMPC holds the potential to accelerate the adoption of flexible robots in
industry.Comment: Submitted to ICRA 202
The monumental landscape transformation of the Island of Babeldaob (Republic of Palau)
Babeldaob is the largest island of Palau. The landscape of this mostly volcanic island is dominated by monumental earthworks, like terraced hills, crown and moat constructions, and modified ridgelines. The majority of the Palau earthworks were built between 2400 and 1200 BP, making them the oldest examples of monumentality in Oceania according to the current state of research. Despite the degree of landscape transformation on Babeldaob, the monumental aspect of the earthworks, and the fact that oral traditions are of utmost importance in the Palauan society, little information about the construction, the function, and significance of them has been passed down. Notwithstanding several archaeological investigations in the last years, questions about the chronology, genesis, function, and use of the earthworks are still open. Did the terraces serve as settlement areas? Have they been used for horticulture? Did they have a ritual or political significance? Or were they used for defence? Using aerial photogrammetry, we generated 3D-models of 14 earthworks that served as a basis for placing test trenches to investigate the construction methods and function of the monuments. Detailed geoarchaeological, geomorphological, pedological, and sedimentological analysis showed many aspects of building techniques, ancient land use, and the high stability of the earthworks
Glycosylated proteins preserved over millennia: N-glycan analysis of Tyrolean Iceman, Scythian Princess and Warrior.
An improved understanding of glycosylation will provide new insights into many biological processes. In the analysis of oligosaccharides from biological samples, a strict regime is typically followed to ensure sample integrity. However, the fate of glycans that have been exposed to environmental conditions over millennia has not yet been investigated. This is also true for understanding the evolution of the glycosylation machinery in humans as well as in any other biological systems. In this study, we examined the glycosylation of tissue samples derived from four mummies which have been naturally preserved: - the 5,300 year old "Iceman called Oetzi", found in the Tyrolean Alps; the 2,400 year old "Scythian warrior" and "Scythian Princess", found in the Altai Mountains; and a 4 year old apartment mummy, found in Vienna/Austria. The number of N-glycans that were identified varied both with the age and the preservation status of the mummies. More glycan structures were discovered in the contemporary sample, as expected, however it is significant that glycan still exists in the ancient tissue samples. This discovery clearly shows that glycans persist for thousands of years, and these samples provide a vital insight into ancient glycosylation, offering us a window into the distant past
Epstein-Barr virus infection is strictly associated with the metastatic spread of sinonasal squamous-cell carcinomas
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