TY - JOUR A1 - Prume, Klaus A1 - Muralt, P. A1 - Calame, F. A1 - Schmitz-Kempen, T. T1 - Piezoelectric thin films: evaluation of electrical and electromechanical characteristics for MEMS devices / Prume, K. ; Muralt, P. ; Calame, F. ; Schmitz-Kempen, T. ; Tiedke, S. ; JF - IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. 54 (2007), H. 1 Y1 - 2007 SN - 0885-3010 SP - 81 EP - 14 ER - TY - JOUR A1 - Prume, Klaus A1 - Meyer, René A1 - Waser, Rainer A1 - Schmitz, Torsten T1 - Dynamic leakage current compensation in ferroelectric thin-film capacitor structures / Meyer, René ; Waser, Rainer ; Prume, Klaus ; Schmitz, Torsten ; Tiedke, Stephan JF - Applied Physics Letters . 86 (2005), H. 14 Y1 - 2005 SN - 0003-6951 SP - 142907-1 EP - 142907-3 ER - TY - JOUR A1 - Prume, Klaus A1 - Gerber, Peter A1 - Kügeler, Carsten A1 - Roelofs, Andreas T1 - Simulation and measurements of the piezoelectric properties response (d33) of piezoelectric layered thin film structures influenced by the top-electrode size / Prume, K. ; Gerber, P. ; Kügeler, C. ; Roelofs, A. ; Böttger, U. ; Waser, R. ; Schmitz-Kempen, Y1 - 2004 SN - 0-7803-8410-5 N1 - 14th IEEE International Symposium on Applications of Ferroelectrics, 2004. ISAF-04. 2004 SP - 7 EP - 10 ER - TY - JOUR A1 - Prume, Klaus A1 - Gerber, P. A1 - Roelofs, A. A1 - Kügeler, C. T1 - Effects of the top-electrode size on the piezoelectric properties (d33 and S) of lead zirconate titanate thin films / Gerber, P. ; Roelofs, A. ; Kügeler, C.; Böttger, U. ; Waser, R. ; Prume, K. ; JF - Journal of Applied Physics . 96 (2004), H. 5 Y1 - 2004 SN - 0021-8979 SP - 2800 EP - 2804 ER - TY - JOUR A1 - Prume, Klaus A1 - Franken, Klaus A1 - Maier, Horst R. A1 - Waser, Rainer T1 - Finite-Element Analysis of Ceramic Multilayer Capacitors: Failure Probability Caused by Wave Soldering and Bending Loads / Franken, Klaus ; Maier, Horst R. ; Prume, Klaus ; Waser, Rainer JF - Journal of the American Ceramic Society. 83 (2000), H. 6 Y1 - 2000 SN - 0002-7820 SP - 1433 EP - 1440 ER - TY - JOUR A1 - Prume, Klaus A1 - Franken, Klaus A1 - Böttger, Ulrich A1 - Waser, Rainer T1 - Modelling and numerical simulation of the electrical, mechanical, and thermal coupled behaviour of Multilayer capacitors (MLCs) / Prume, Klaus ; Franken, Klaus ; Böttger, Ulrich ; Waser, Rainer ; Maier, Horst R. JF - Journal of the European Ceramic Society. 22 (2002), H. 8 Y1 - 2002 SN - 0955-2219 SP - 1285 EP - 1296 ER - TY - JOUR A1 - Prume, Klaus A1 - Booij, W. E. A1 - Vogl, A. H. A1 - Wang, D. T. T1 - A simple and powerful analytical model for MEMS piezoelectric multimorphs / Booij, W. E. ; Vogl, A. H. ; Wang, D. T. ; Tyholdt, F. ; Ostbo, N. P. ; Raeder, H. ; Prume, K. JF - Journal of Electroceramics. 19 (2007), H. 4 Y1 - 2007 SN - 1385-3449 SP - 387 EP - 393 ER - TY - JOUR A1 - Prume, Klaus T1 - Electrical and electromechanical characterization of piezoelectric thin films in view of MEMS application / Tiedke, S. ; Prume, K. ; Schmitz-Kempen, T.; Y1 - 2007 N1 - ISAF 2007. Sixteenth IEEE International Symposium on Applications of Ferroelectrics, 2007 SP - 702 ER - TY - JOUR A1 - Prochnow, Nora A1 - Gebing, Tina A1 - Ladage, Kerstin A1 - Krause-Finkeldey, Dorothee A1 - Ourdi, Abessamad El A1 - Bitz, Andreas A1 - Streckert, Joachim A1 - Hansen, Volkert A1 - Dermietzel, Rolf T1 - Electromagnetic field effect or simply stress? Effects of UMTS exposure on hippocampal longterm plasticity in the context of procedure related hormone release JF - PLoS one N2 - Harmful effects of electromagnetic fields (EMF) on cognitive and behavioural features of humans and rodents have been controversially discussed and raised persistent concern about adverse effects of EMF on general brain functions. In the present study we applied radio-frequency (RF) signals of the Universal Mobile Telecommunications System (UMTS) to full brain exposed male Wistar rats in order to elaborate putative influences on stress hormone release (corticosteron; CORT and adrenocorticotropic hormone; ACTH) and on hippocampal derived synaptic long-term plasticity (LTP) and depression (LTD) as electrophysiological hallmarks for memory storage and memory consolidation. Exposure was computer controlled providing blind conditions. Nominal brain-averaged specific absorption rates (SAR) as a measure of applied mass-related dissipated RF power were 0, 2, and 10 W/kg over a period of 120 min. Comparison of cage exposed animals revealed, regardless of EMF exposure, significantly increased CORT and ACTH levels which corresponded with generally decreased field potential slopes and amplitudes in hippocampal LTP and LTD. Animals following SAR exposure of 2 W/kg (averaged over the whole brain of 2.3 g tissue mass) did not differ from the sham-exposed group in LTP and LTD experiments. In contrast, a significant reduction in LTP and LTD was observed at the high power rate of SAR (10 W/kg). The results demonstrate that a rate of 2 W/kg displays no adverse impact on LTP and LTD, while 10 W/kg leads to significant effects on the electrophysiological parameters, which can be clearly distinguished from the stress derived background. Our findings suggest that UMTS exposure with SAR in the range of 2 W/kg is not harmful to critical markers for memory storage and memory consolidation, however, an influence of UMTS at high energy absorption rates (10 W/kg) cannot be excluded. Y1 - 2011 U6 - http://dx.doi.org/10.1371/journal.pone.0019437 VL - 6 IS - 5 PB - PLOS CY - San Francisco ER - TY - JOUR A1 - Oßmann, Martin A1 - Kazay, B. T1 - Simple circuit provides high-side current sensing / Ossmann, M ; Kazay, B. JF - EDN. 45 (2000), H. 21 Y1 - 2000 SN - 0012-7515 SP - 200 EP - 200 ER - TY - JOUR A1 - Oßmann, Martin A1 - Kazay, B. T1 - Single mu C pin makes half-duplex RS-232C / Ossmann, M JF - EDN. 44 (1999), H. 16 Y1 - 1999 SN - 0012-7515 SP - 118 ER - TY - JOUR A1 - Oßmann, Martin A1 - Hattrup, C. A1 - Broeck, H. W. van der T1 - Fast estimation techniques for digital control of resonant converters / Hattrup, C.; van der Broeck, H.W.; Ossmann, M.; JF - IEEE Transaction on Power Electronics. 18 (2003), H. 1 Y1 - 2003 SN - 0885-8993 N1 - Part 2 SP - 365 EP - 372 ER - TY - JOUR A1 - Orzada, Stephan A1 - Solbach, Klaus A1 - Gratz, Marcel A1 - Brunheim, Sascha A1 - Fiedler, Thomas M. A1 - Johst, Sören A1 - Bitz, Andreas A1 - Shooshtary, Samaneh A1 - Abuelhaija, Asjraf A1 - Voelker, Maximilian N. A1 - Rietsch, Stefan H. G. A1 - Kraff, Oliver A1 - Maderwald, Stefan A1 - Flöser, Martina A1 - Oehmingen, Mark A1 - Quick, Harald H. A1 - Ladd, Mark E. T1 - A 32-channel parallel transmit system add-on for 7T MRI JF - Plos one Y1 - 2019 U6 - http://dx.doi.org/10.1371/journal.pone.0222452 ER - TY - JOUR A1 - Orzada, Stephan A1 - Maderwald, Stefan A1 - Poser, Benedikt Andreas A1 - Bitz, Andreas A1 - Quick, Harald H. A1 - Ladd, Mark E. T1 - RF excitation using time interleaved acquisition of modes (TIAMO) to address B1 inhomogeneity in high-field MRI JF - Magnetic Resonance in Medicine N2 - As the field strength and, therefore, the operational frequency in MRI is increased, the wavelength approaches the size of the human head/body, resulting in wave effects, which cause signal decreases and dropouts. Several multichannel approaches have been proposed to try to tackle these problems, including RF shimming, where each element in an array is driven by its own amplifier and modulated with a certain (constant) amplitude and phase relative to the other elements, and Transmit SENSE, where spatially tailored RF pulses are used. In this article, a relatively inexpensive and easy to use imaging scheme for 7 Tesla imaging is proposed to mitigate signal voids due to B1 field inhomogeneity. Two time-interleaved images are acquired using a different excitation mode for each. By forming virtual receive elements, both images are reconstructed together using GRAPPA to achieve a more homogeneous image, with only small SNR and SAR penalty in head and body imaging at 7 Tesla. Y1 - 2010 U6 - http://dx.doi.org/10.1002/mrm.22527 SN - 1522-2594 VL - 64 IS - 2 SP - 327 EP - 333 PB - Wiley-Liss CY - New York ER - TY - JOUR A1 - Orzada, Stephan A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - A method to approximate maximum local SAR in multichannel transmit MR systems without transmit phase information JF - Magnetic Resonance in Medicine N2 - Purpose To calculate local specific absorption rate (SAR) correctly, both the amplitude and phase of the signal in each transmit channel have to be known. In this work, we propose a method to derive a conservative upper bound for the local SAR, with a reasonable safety margin without knowledge of the transmit phases of the channels. Methods The proposed method uses virtual observation points (VOPs). Correction factors are calculated for each set of VOPs that prevent underestimation of local SAR when the VOPs are applied with the correct amplitudes but fixed phases. Results The proposed method proved to be superior to the worst-case calculation based on the maximum eigenvalue of the VOPs. The mean overestimation for six coil setups could be reduced, whereas no underestimation of the maximum local SAR occurred. In the best investigated case, the overestimation could be reduced from a factor of 3.3 to a factor of 1.7. Conclusion The upper bound for the local SAR calculated with the proposed method allows a fast estimation of the local SAR based on power measurements in the transmit channels and facilitates SAR monitoring in systems that do not have the capability to monitor transmit phases Y1 - 2016 U6 - http://dx.doi.org/10.1002/mrm.26398 SN - 1522-2594 VL - 78 IS - 2 SP - 805 EP - 811 PB - International Society for Magnetic Resonance in Medicine ER - TY - JOUR A1 - Orzada, Stephan A1 - Johst, Sören A1 - Maderwald, Stefan A1 - Bitz, Andreas A1 - Solbach, Klaus A1 - Ladd, Mark E. T1 - Mitigation of B1(+) inhomogeneity on single-channel transmit systems with TIAMO JF - Magnetic Resonance in Medicine Y1 - 2013 U6 - http://dx.doi.org/10.1002/mrm.24453 SN - 1522-2594 VL - 70 IS - 1 SP - 290 EP - 294 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Orzada, Stephan A1 - Fiedler, Thomas M. A1 - Bitz, Andreas A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - Local SAR compression with overestimation control to reduce maximum relative SAR overestimation and improve multi-channel RF array performance JF - Magnetic Resonance Materials in Physics, Biology and Medicine N2 - Objective In local SAR compression algorithms, the overestimation is generally not linearly dependent on actual local SAR. This can lead to large relative overestimation at low actual SAR values, unnecessarily constraining transmit array performance. Method Two strategies are proposed to reduce maximum relative overestimation for a given number of VOPs. The first strategy uses an overestimation matrix that roughly approximates actual local SAR; the second strategy uses a small set of pre-calculated VOPs as the overestimation term for the compression. Result Comparison with a previous method shows that for a given maximum relative overestimation the number of VOPs can be reduced by around 20% at the cost of a higher absolute overestimation at high actual local SAR values. Conclusion The proposed strategies outperform a previously published strategy and can improve the SAR compression where maximum relative overestimation constrains the performance of parallel transmission. Y1 - 2020 SN - 1352-8661 U6 - http://dx.doi.org/10.1007/s10334-020-00890-0 IS - 34 (2021) SP - 153 EP - 164 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Orzada, Stephan A1 - Bitz, Andreas A1 - Schäfer, Lena C. A1 - Ladd, Susanne C. A1 - Ladd, Mark E. A1 - Maderwald, Stefan T1 - Open design eight-channel transmit/receive coil for high-resolution and real-time ankle imaging at 7 T JF - Medical Physics N2 - Purpose: At 1.5 T, real-time MRI of joint movement has been shown to be feasible. However, 7 T, provides higher SNR and thus an improved potential for parallel imaging acceleration. The purpose of this work was to build an open, U-shaped eight-channel transmit/receive microstrip coil for 7 T MRI to enable high-resolution and real-time imaging of the moving ankle joint. Methods: A U-shaped eight-channel transmit/receive array for the human ankle was built.urn:x-wiley:00942405:mp3399:equation:mp3399-math-0001-parameters and urn:x-wiley:00942405:mp3399:equation:mp3399-math-0002-factor were measured. SAR calculations of different ankle postures were performed to ensure patient safety. Inhomogeneities in the transmit field consequent to the open design were compensated for by the use of static RF shimming. High-resolution and real-time imaging was performed in human volunteers. Results: The presented array showed good performance with regard to patient comfort and image quality. High acceleration factors of up to 4 are feasible without visible acceleration artifacts. Reasonable image homogeneity was achieved with RF shimming. Conclusions: Open, noncylindrical designs for transmit/receive coils are practical at 7 T and real-time imaging of the moving joint is feasible with the presented coil design. Y1 - 2011 U6 - http://dx.doi.org/10.1118/1.3553399 SN - 2473-4209 VL - 38 IS - 3 SP - 1162 EP - 1167 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Orzada, Stephan A1 - Bitz, Andreas A1 - Johst, Sören A1 - Gratz, Marcel A1 - Völker, Maximilian N. A1 - Kraff, Oliver A1 - Abuelhaija, Ashraf A1 - Fiedler, Thomas M. A1 - Solbach, Klaus A1 - Quick, Harald H. A1 - Ladd, Mark E. T1 - Analysis of an integrated 8-Channel Tx/Rx body array for use as a body coil in 7-Tesla MRI JF - Frontiers in Physics Y1 - 2017 U6 - http://dx.doi.org/10.3389/fphy.2017.00017 SN - 2296-424X N1 - Article number 17 VL - 5 IS - Jun ER - TY - JOUR A1 - Orzada, S. A1 - Maderwald, S. A1 - Poser, B. A. A1 - Johst, S. A1 - Kannengiesser, S. A1 - Ladd, M. E. A1 - Bitz, Andreas T1 - Time-interleaved acquisition of modes: an analysis of SAR and image contrast implications JF - Magnetic Resonance in Medicine N2 - s the magnetic field strength and therefore the operational frequency in MRI are increased, the radiofrequency wavelength approaches the size of the human head/body, resulting in wave effects which cause signal decreases and dropouts. Especially, whole-body imaging at 7 T and higher is therefore challenging. Recently, an acquisition scheme called time-interleaved acquisition of modes has been proposed to tackle the inhomogeneity problems in high-field MRI. The basic premise is to excite two (or more) different Burn:x-wiley:07403194:media:MRM23081:tex2gif-stack-1 modes using static radiofrequency shimming in an interleaved acquisition, where the complementary radiofrequency patterns of the two modes can be exploited to improve overall signal homogeneity. In this work, the impact of time-interleaved acquisition of mode on image contrast as well as on time-averaged specific absorption rate is addressed in detail. Time-interleaved acquisition of mode is superior in Burn:x-wiley:07403194:media:MRM23081:tex2gif-stack-2 homogeneity compared with conventional radiofrequency shimming while being highly specific absorption rate efficient. Time-interleaved acquisition of modes can enable almost homogeneous high-field imaging throughout the entire field of view in PD, T2, and T2*-weighted imaging and, if a specified homogeneity criterion is met, in T1-weighted imaging as well. Y1 - 2012 U6 - http://dx.doi.org/10.1002/mrm.23081 SN - 1522-2594 VL - 67 IS - 4 SP - 1033 EP - 1041 PB - Wiley-Liss CY - New York ER -