Entity

Time filter

Source Type


Bauer G.,Albert Ludwigs University of Freiburg | Zarkovic N.,Ruder Boskovic Institute | Zarkovic N.,University of Applied science
Free Radical Biology and Medicine | Year: 2015

Tumor cells generate extracellular superoxide anions and are protected against superoxide anion-mediated intercellular apoptosis-inducing signaling by the expression of membrane-associated catalase. 4-Hydroxy-2-nonenal (4-HNE), a versatile second messenger generated during lipid peroxidation, has been shown to induce apoptosis selectively in malignant cells. The findings described in this paper reveal the strong, concentration-dependent potential of 4-HNE to specifically inactivate extracellular catalase of tumor cells both indirectly and directly and to consequently trigger apoptosis in malignant cells through superoxide anion-mediated intercellular apoptosis-inducing signaling. Namely, 4-HNE caused apoptosis selectively in NOX1-expressing tumor cells through inactivation of their membrane-associated catalase, thus reactivating subsequent intercellular signaling through the NO/peroxynitrite and HOCl pathways, followed by the mitochondrial pathway of apoptosis. Concentrations of 4-HNE of 1.2 μM and higher directly inactivated membrane-associated catalase of tumor cells, whereas at lower concentrations, 4-HNE triggered a complex amplificatory pathway based on initial singlet oxygen formation through H2O2 and peroxynitrite interaction. Singlet-oxygen-dependent activation of the FAS receptor and caspase-8 increased superoxide anion generation by NOX1 and amplification of singlet oxygen generation, which allowed singlet-oxygen-dependent inactivation of catalase. 4-HNE and singlet oxygen cooperate in complex autoamplificatory loops during this process. The finding of these novel anticancer pathways may be useful for understanding the role of 4-HNE in the control of malignant cells and for the optimization of ROS-dependent therapeutic approaches including antioxidant treatments. © 2015 Elsevier Inc. All rights reserved. Source


Cappon H.,University of Applied science | Cappon H.,Center of Excellence for Sustainable Water Technology | Keesman K.J.,Wageningen University
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2012

Design of ultrasonic equipment is frequently facilitated with numerical models. These numerical models, however, need a calibration step, because usually not all characteristics of the materials used are known. Characterization of material properties combined with numerical simulations and experimental data can be used to acquire valid estimates of the material parameters. In our design application, a finite element (FE) model of an ultrasonic particle separator, driven by an ultrasonic transducer in thickness mode, is required. A limited set of material parameters for the piezoelectric transducer were obtained from the manufacturer, thus preserving prior physical knowledge to a large extent. The remaining unknown parameters were estimated from impedance analysis with a simple experimental setup combined with a numerical optimization routine using 2-D and 3-D FE models. Thus, a full set of physically interpretable material parameters was obtained for our specific purpose. The approach provides adequate accuracy of the estimates of the material parameters, near 1%. These parameter estimates will subsequently be applied in future design simulations, without the need to go through an entire series of characterization experiments. Finally, a sensitivity study showed that small variations of 1% in the main parameters caused changes near 1% in the eigenfrequency, but changes up to 7% in the admittance peak, thus influencing the efficiency of the system. Temperature will already cause these small variations in response; thus, a frequency control unit is required when actually manufacturing an efficient ultrasonic separation system. © 2012 IEEE. Source


Kovacs T.,Hungarian Academy of Sciences | Kovacs T.,University of Applied science | Regaly Zs.,Hungarian Academy of Sciences
Astrophysical Journal Letters | Year: 2015

The circular restricted three-body problem is investigated in the context of accretion and scattering processes. In our model, a large number of identical non-interacting mass-less planetesimals are considered in the planar case orbiting a star-planet system. This description allows us to investigate the gravitational scattering and possible capture of the particles by the forming planetary embryo in a dynamical systems approach. Although the problem serves a large variety of complex motions, the results can be easily interpreted because of the low dimensionality of the phase space. We show that initial conditions define isolated regions of the disk, where planetesimals accrete or escape, which have, in fact, a fractal structure. The fractal geometry of these "basins" implies that the dynamics is very complex. Based on the calculated escape rates and escape times, it is also demonstrated that the planetary accretion rate is exponential for short times and follows a power law for longer integration. A new numerical calculation of the maximum mass that a planet can reach (described by the expression of the isolation mass) is also derived. © 2015. The American Astronomical Society. All rights reserved. Source


Cappon H.,University of Applied science | Keesman K.,Wageningen University
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2013

Our overall goal is to apply acoustic separation technology for the recovery of valuable particulate matter from wastewater in industry. Such large-scale separator systems require detailed design and evaluation to optimize the system performance at the earliest stage possible. Numerical models can facilitate and accelerate the design of this application; therefore, a finite element (FE) model of an ultrasonic particle separator is a prerequisite. In our application, the particle separator consists of a glass resonator chamber with a piezoelectric transducer attached to the glass by means of epoxy adhesive. Separation occurs most efficiently when the system is operated at its main eigenfrequency. The goal of the paper is to calibrate and validate a model of a demonstrator ultrasonic separator, preserving known physical parameters and estimating the remaining unknown or less-certain parameters to allow extrapolation of the model beyond the measured system. A two-step approach was applied to obtain a validated model of the separator. The first step involved the calibration of the piezoelectric transducer. The second step, the subject of this paper, involves the calibration and validation of the entire separator using nonlinear optimization techniques. The results show that the approach lead to a fully calibrated 2-D model of the empty separator, which was validated with experiments on a filled separator chamber. The large sensitivity of the separator to small variations indicated that such a system should either be made and operated within tight specifications to obtain the required performance or the operation of the system should be adaptable to cope with a slightly off-spec system, requiring a feedback controller. © 1986-2012 IEEE. Source


Jokimaki J.,University of Lapland | Jokimaki J.,University of Applied science | Kaisanlahti-Jokimaki M.-L.,University of Lapland
Ornis Fennica | Year: 2012

Wintertime ecological studies conducted in different kinds of residential areas over several winters have thus far been lacking. The objective of this study was to analyze if the between-winter variability of bird communities differs between urban residential habitat types. The study was conducted in five blocks of flats areas, five single-family house areas, and five villages inRovaniemi, northern Finland, during fivewinters.Birdswere surveyed using a single-visit study plot (30 ha) method. The average between-winter variation (CV%) in bird species richness was 27% and in bird abundance was 53%, and these values did not differ between the three types of residential areas. Temporal variation of species in residential areas was species-specific. The lowest between-winter variation was observed for omnivore or feeding table species such as the Great tit Parus major (50%),Magpie Pica pica (53%) and House Sparrow Passer domesticus (76%). The highest variation was observed for berry-eating species, such as the Bullfinch Pyrrhula pyrrhula (196%) andWaxwing Bombycilla garrulus (192%). The between-winter variation (CV%) of abundance ofmost species was greater in the blocks of flats areas than in the other residential-area types. The between-winter average qualitative similarity was 76.1% in the blocks of flats areas, 80.0% in the single-family house areas, and 78.0% in the villages, and these values did not differ between types of residential areas or between studywinters. Stability of winter communities decreased fromthe centre to the periphery of Rovaniemi.We suggest that the stabilizing, warmer microclimate near the urban core of the town partly explains this result. The average species turnover rate (%) in the block of flats areas was 22.8, in single-family house areas was 20.5, and in the villageswas 21.6. In general, the lowest between-winter similarities, highest species turnover rates, and the highest between-winter variation of abundance of individual species were observed in areas of blocks of flats. Our results suggest that single-family house and village areas are better overwintering areas forwintering birds than areas of blocks-of-flats. Intensivewinter feedingmight stabilize the between-winter variation of bird assemblages especially in single-family house areas. In addition, the warmer microclimate near the urban core might probably also stabilizes variation in residential bird assemblages. Source

Discover hidden collaborations