Complex Mechanisms of Antimony Genotoxicity in Budding Yeast Involves Replication and Topoisomerase I-Associated DNA Lesions,Telomere Dysfunction and Inhibition of DNA Repair

Antimony is a toxic metalloid with poorly understood mechanisms of toxicity and uncertain carcinogenic properties. By using a combination of genetic, biochemical and DNA damage assays, we investigated the genotoxic potential of trivalent antimony in the model organism Saccharomyces cerevisiae. We found that low doses of Sb(III) generate various forms of DNA damage including replication and topoisomerase I-dependent DNA lesions as well as oxidative stress and replication-independent DNA breaks accompanied by activation of DNA damage checkpoints and formation of recombination repair centers. At higher concentrations of Sb(III), moderately increased oxidative DNA damage is also observed. Consistently, base excision, DNA damage tolerance and homologous recombination repair pathways contribute to Sb(III) tolerance. In addition, we provided evidence suggesting that Sb(III) causes telomere dysfunction. Finally, we showed that Sb(III) negatively effects repair of double-strand DNA breaks and distorts actin and microtubule cytoskeleton. In sum, our results indicate that Sb(III) exhibits a significant genotoxic activity in budding yeast.     

Control System for Free-Floating Space Manipulator Based on Nonlinear Model Predictive Control (NMPC)

Manipulator mounted on an unmanned satellite could be used for performing orbital capture maneuver in order to repair satellites or remove space debris from orbit. Use of manipulators for such purposes presents unique challenges, as high level of autonomy is required and the motion of the manipulator influences the position and orientation of the manipulator-equipped satellite. This paper presents a new control system that consists of two modules: trajectory planning module (based on trajectory optimization algorithm) and Model Predictive Controller. Both modules take into account the free-floating nature of the satellite-manipulator system. Proposed control system was tested in numerical simulations performed for a simplified planar case. In the first set of simulations Nonlinear Model Predictive Control (NMPC) was used to ensure realization of a square reference end-effector trajectory, while in the second set control system was used for optimizing and then ensuring realization of the trajectory that leads to grasping of the rotating target satellite. Simulations were performed with disturbances and with the assumed non-perfect knowledge of parameters of the satellite-manipulator system. Results obtained with NMPC are better than results obtained with the controller based on the Dynamic Jacobian inverse and with the Modified Simple Adaptive Control (MSAC).     

Ermüdungsfestigkeit von hochfestem Beton unter Druckbeanspruchung

Fatigue behaviour of high strength concrete under compression. The fatigue strength of high performance concrete (HPC) was experimentally investigated with ca. 170 specimens. The results show that the fatigue behaviour of HPC differs from that of the normal strength concrete (NSC). In the regions of maximum compressive stress level higher than the elasticity limit, the fatigue strength of HPC seems smaller than those of NSC. In the remaining regions the behaviour of HPC is comparable with the behaviour of NSC. The stress redistribution within the compression zone with different stress amplitude seems also smaller than those of NSC. Additional investigations are necessary in order to formulate design rules for constructions made of HPC.     

Phase studies on the quasi-binary thallium(I) selenide-thallium(I) telluride system

The phase diagram for the system Tl₂Te-Tl₂Se has been determined on the basis of the results of studies by means of common thermal analysis. The diagram has been compared with diagrams published earlier. Some regularities have been presented for the quasi-binary chalcogenide systems with common cation.     

Analysis of experimental conditions for simultaneous measurements of transport and magnetotransport coefficients of high temperature superconductors

Experimental conditions for simultaneous measurements of transport coefficients of high temperature superconductors in zero and non-zero magnetic fields are analysed. Test measurements of the thermal conductivity, the thermoelectric power and the Nernst-Ettingshausen effect of a textured Bi2212 sample are reported in an external magnetic field of 2 T. Errors related to parameters of the thermocouple used and to the spurious heat flows are discussed for a new experimental set-up built based on a closed cycle helium refrigerator. Possible optimising of experimental conditions is suggested.