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23 results on '"Heer, Rudolf"'

3. Fundamental switching field distribution of a single domain particle derived from the N\'eel-Brown model

Author

Breth, Leoni, Suess, Dieter, Vogler, Christoph, Bergmair, Bernhard, Fuger, Markus, Heer, Rudolf, and Brueckl, Hubert

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We present an analytical derivation of the switching field distribution for a single domain particle from the N\'eel-Brown model in the presence of a linearly swept magnetic field and influenced by thermal fluctuations. We show that the switching field distribution corresponds to a probability density function and can be obtained by solving a master equation for the not-switching probability together with the transition rate for the magnetization according to the Arrhenius-N\'eel Law. By calculating the first and second moments of the probability density function we succeed in modeling rate-dependent coercivity and the standard deviation of the coercive field. Complementary to the analytical approach, we also present a Monte Carlo simulation for the switching of a macrospin, which allows us to account for the field dependence of the attempt frequency. The results show excellent agreement with results from a Langevin dynamics simulation and therefore point out the importance to include the relevant dependencies in the attempt frequency. However, we conclude that the N\'eel-Brown model fails to predict switching fields correctly for common field rates and material parameters used in magnetic recording from the loss of normalization of the probability density function. Investigating the transition regime between thermally assisted and dynamic switching will be of future interest regarding the development of new magnetic recording technologies.

Published
2011

7. Cell imaging in microfluidic channels

Author

Schrittwieser, Stefan, Krieger, Sigurd, Geleff, Silvana, Scholz, Gregor, Bezshlyakh, Daria, Wasisto, Hutomo Suryo, Waag, Andreas, Schotter, Jörg, Heer, Rudolf, Neuhaus, Winfried, Brachner, Andreas, Kothe, Tim, Eggeling, Moritz, and Vogelbacher, Florian

Abstract

Talk at the ChipScope Symposium at the 4th international nanoFIS 2020 conference, held online.

Published
2020
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10. High-sensitivity plasmo-photonic interferometric sensors on a chip

Author

Chatzianagnostou, Evangelia, primary, Manolis, Athanasios, additional, Dabos, George, additional, Ketzaki, Dimitra, additional, Chmielak, Bartos, additional, Giesecke, Anna-Lena, additional, Porschatis, Caroline, additional, Cegielski, Piotr J., additional, Suckow, Stephan, additional, Markey, Laurent, additional, Weeber, Jean-Claude, additional, Dereux, Alain, additional, Schrittwieser, Stefan, additional, Heer, Rudolf, additional, Pleros, Nikos, additional, and Tsiokos, Dimitris, additional

Published
2020
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12. Acute Exercise Increases the Expression of KIR2DS4 by Promoter Demethylation in NK Cells

Author

Schenk, Alexander, Pulverer, Walter, Koliamitra, Christine, Bauer, Claus Juergen, Ilic, Suzana, Heer, Rudolf, Schier, Robert, Schick, Volker, Boettiger, Bernd W., Gerhaeuser, Clarissa, Bloch, Wilhelm, Zimmer, Philipp, Schenk, Alexander, Pulverer, Walter, Koliamitra, Christine, Bauer, Claus Juergen, Ilic, Suzana, Heer, Rudolf, Schier, Robert, Schick, Volker, Boettiger, Bernd W., Gerhaeuser, Clarissa, Bloch, Wilhelm, and Zimmer, Philipp

Abstract

Positive effects of exercise on cancer prevention and progression have been proposed to be mediated by stimulating natural killer (NK) cells. Because NK cell receptors are regulated by epigenetic modifications, we investigated whether acute aerobic exercise and training change promoter DNA methylation and gene expression of the activating KIR2DS4 and the inhibiting KIR3DL1 gene. Sixteen healthy women (50-60 years) performed a graded exercise test (GXT) and were randomized into either a passive control group or an intervention group performing a four-week endurance exercise intervention. Blood samples (pre-, post-GXT and post-training) were used for isolation of DNA/RNA of NK cells to assess DNA promoter methylation by targeted deep-amplicon sequencing and gene expression by qRT-PCR. Potential changes in NK cell subsets were determined by flow cytometry. Acute and chronic exercise did not provoke significant alterations of NK cell proportions. Promoter methylation decreased and gene expression increased for KIR2DS4 after acute exercise. A high gene expression correlated with a low methylation of CpGs that were altered by acute exercise. Chronic exercise resulted in a minor decrease of DNA methylation and did not alter gene expression. Acute exercise provokes epigenetic modifications, affecting the balance between the activating KIR2DS4 and the inhibiting KIR3DL1 , with potential benefits on NK cell function.

Published
2019

15. Towards Recycled Paper Based Impedance Biosensor with Wireless Readout

Author

Melnik, Eva, primary, Muschlin, Iris, additional, Wildauer, Agnes, additional, Raskovic, Mirco, additional, Schotter, Joerg, additional, Heilmann, Michael, additional, Ide, Dirk, additional, Borinski, Michael, additional, Lieberzeit, Peter, additional, Kataeva, Nadezhda, additional, Mutinati, Giorgio C., additional, Heer, Rudolf, additional, and Hainberger, Rainer, additional

Published
2017
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23. Signal Generator for Wireless Impedance Monitoring of Microbiological Systems.

Author

Wissenwasser, Jürgen, Vellekoop, Michael J., and Heer, Rudolf

Subjects
SIGNAL generators, WIRELESS communications, ELECTRIC impedance, MICROBIOLOGY, MICROCONTROLLERS, FORCE & energy, HARMONIC analysis (Mathematics)
Abstract

This paper presents a small microcontroller-based sine-wave generator for probe signals of a wide range of amplitudes and frequencies, which requires very little energy so that it can be used for wireless applications in biosensing. The presented realization generates a 10-kHz sine wave with a 100-mV peak-to-peak voltage. Its total harmonic distortion is less than 0.15%, and the spurious free dynamic range excluding harmonics is about 85 dB. The generator's total power consumption at a 3.3-V supply voltage and without output buffers is less than 3.5 mW. This value includes the power requirement of the microcontroller's internal 8-MHz clock generator and is below the power needs of current direct-digital-synthesis-based signal generators. The presented concept bases on commercially available electronic components and is implemented for probe signal generation in wireless batteryless tags for long-term impedance measurements on standard microbiological cell cultures. The included microcontroller enables the use of a phase-controlled trigger signal and other simultaneous control functions, e.g., for peripheral components and data communication. [ABSTRACT FROM AUTHOR]

Published
2011
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