@article{OlbertzThiergart2010, author = {Olbertz, Klaus and Thiergart, Kirsten}, title = {B{\"o}rsengang leicht gemacht? Gesellschafts- und arbeitsrechtliche Aspekte bei {\"U}bernahme und Verschmelzung eines Zielunternehmens auf die SPAC in der Rechtsform der SE}, series = {Betriebs-Berater: BB ; Recht, Wirtschaft, Steuern}, journal = {Betriebs-Berater: BB ; Recht, Wirtschaft, Steuern}, publisher = {Beck}, address = {M{\"u}nchen}, issn = {0340-7918}, pages = {1547}, year = {2010}, abstract = {Die SPAC-SE ist b{\"o}rsenf{\"a}hig und damit eine f{\"u}r eine SPAC grunds{\"a}tzlich geeignete Rechtsform. Die Tatsache, dass es sich hierbei (zun{\"a}chst) um eine leere, arbeitnehmerlose H{\"u}lle handelt, {\"a}ndert hieran nichts. Die Gr{\"u}ndung einer solchen Vorrats-SE ist trotz fehlender Arbeitnehmerbeteiligung unter teleologischer Reduktion von Art. 12 II SE-VO zul{\"a}ssig. Im Gegenzug muss die Arbeitnehmerbeteiligung gemaß \S 18 III SEBG analog nachgeholt werden, wenn das sp{\"a}ter erworbene Zielunternehmen auf die SPAC-SE verschmolzen werden soll. Aus gesellschaftsrechtlicher Sicht ist zu beachten, dass die SPAC-SE mit Sitz in Deutschland, welche auch den deutschen, aktienrechtlichen Bestimmungen unterliegt, nur bedingt f{\"u}r eine SPAC geeignet erscheint. Das deutsche Aktienrecht enth{\"a}lt strenge Regelungen, die der f{\"u}r eine SPAC-SE erforderlichen Flexibilit{\"a}t entgegenstehen k{\"o}nnen. Dies gilt insbesondere f{\"u}r das Erfordernis der Zustimmung der Hauptversammlung zur Akquisition des Zielunternehmens, die R{\"u}ckzahlung des Treuhandverm{\"o}gens an Aktion{\"a}re, die der Akquisition nicht zugestimmt haben und die Liquidation der SPAC-SE im Falle des Scheiterns des Erwerbs des Zielobjektes.}, language = {de} } @inproceedings{OlderogMohrBegingetal.2021, author = {Olderog, M. and Mohr, P. and Beging, Stefan and Tsoumpas, C. and Ziemons, Karl}, title = {Simulation study on the role of tissue-scattered events in improving sensitivity for a compact time of flight compton positron emission tomograph}, series = {2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)}, booktitle = {2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)}, publisher = {IEEE}, address = {New York, NY}, isbn = {978-1-7281-7693-2}, doi = {10.1109/NSS/MIC42677.2020.9507901}, pages = {4 Seiten}, year = {2021}, abstract = {In positron emission tomography improving time, energy and spatial detector resolutions and using Compton kinematics introduces the possibility to reconstruct a radioactivity distribution image from scatter coincidences, thereby enhancing image quality. The number of single scattered coincidences alone is in the same order of magnitude as true coincidences. In this work, a compact Compton camera module based on monolithic scintillation material is investigated as a detector ring module. The detector interactions are simulated with Monte Carlo package GATE. The scattering angle inside the tissue is derived from the energy of the scattered photon, which results in a set of possible scattering trajectories or broken line of response. The Compton kinematics collimation reduces the number of solutions. Additionally, the time of flight information helps localize the position of the annihilation. One of the questions of this investigation is related to how the energy, spatial and temporal resolutions help confine the possible annihilation volume. A comparison of currently technically feasible detector resolutions (under laboratory conditions) demonstrates the influence on this annihilation volume and shows that energy and coincidence time resolution have a significant impact. An enhancement of the latter from 400 ps to 100 ps leads to a smaller annihilation volume of around 50\%, while a change of the energy resolution in the absorber layer from 12\% to 4.5\% results in a reduction of 60\%. The inclusion of single tissue-scattered data has the potential to increase the sensitivity of a scanner by a factor of 2 to 3 times. The concept can be further optimized and extended for multiple scatter coincidences and subsequently validated by a reconstruction algorithm.}, language = {en} } @article{OliveiraMolinnusBegingetal.2021, author = {Oliveira, Danilo A. and Molinnus, Denise and Beging, Stefan and Siqueira Jr, Jos{\´e} R. and Sch{\"o}ning, Michael Josef}, title = {Biosensor Based on Self-Assembled Films of Graphene Oxide and Polyaniline Using a Field-Effect Device Platform}, series = {physica status solidi (a) applications and materials science}, volume = {218}, journal = {physica status solidi (a) applications and materials science}, number = {13}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.202000747}, pages = {1 -- 9}, year = {2021}, abstract = {A new functionalization method to modify capacitive electrolyte-insulator-semiconductor (EIS) structures with nanofilms is presented. Layers of polyallylamine hydrochloride (PAH) and graphene oxide (GO) with the compound polyaniline:poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA) are deposited onto a p-Si/SiO2 chip using the layer-by-layer technique (LbL). Two different enzymes (urease and penicillinase) are separately immobilized on top of a five-bilayer stack of the PAH:GO/PANI:PAAMPSA-modified EIS chip, forming a biosensor for detection of urea and penicillin, respectively. Electrochemical characterization is performed by constant capacitance (ConCap) measurements, and the film morphology is characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). An increase in the average sensitivity of the modified biosensors (EIS-nanofilm-enzyme) of around 15\% is found in relation to sensors, only carrying the enzyme but without the nanofilm (EIS-enzyme). In this sense, the nanofilm acts as a stable bioreceptor onto the EIS chip improving the output signal in terms of sensitivity and stability.}, language = {en} } @book{Olk1980, author = {Olk, Ulrich}, title = {Entwicklung eines Struktur- und Ablaufmodells f{\"u}r industrialisiertes Bauen}, pages = {III, 198 S. : graph. Darst.}, year = {1980}, language = {de} } @article{Olk2006, author = {Olk, Ulrich}, title = {Arbeitsvorbereitung und Ablaufplanung}, series = {Zahlentafeln f{\"u}r den Baubetrieb / Hoffmann, Manfred ; Kuhlmann, Willy [Hrsg.]. 7., vollst. {\"u}berarb. Aufl.}, journal = {Zahlentafeln f{\"u}r den Baubetrieb / Hoffmann, Manfred ; Kuhlmann, Willy [Hrsg.]. 7., vollst. {\"u}berarb. Aufl.}, publisher = {Teubner}, address = {Wiesbaden}, isbn = {3-519-65220-X}, pages = {547 -- 580}, year = {2006}, language = {de} } @article{Olk2006, author = {Olk, Ulrich}, title = {Unfallverh{\"u}tung}, series = {Zahlentafeln f{\"u}r den Baubetrieb / Hoffmann, Manfred ; Kuhlmann, Willy [Hrsg.]. 7., vollst. {\"u}berarb. Aufl.}, journal = {Zahlentafeln f{\"u}r den Baubetrieb / Hoffmann, Manfred ; Kuhlmann, Willy [Hrsg.]. 7., vollst. {\"u}berarb. Aufl.}, publisher = {Teubner}, address = {Wiesbaden}, isbn = {3-519-65220-X}, pages = {833 -- 929}, year = {2006}, language = {de} } @article{Olk2006, author = {Olk, Ulrich}, title = {Arbeitsvorbereitung und Ablaufplanung}, series = {Beispiele f{\"u}r die Baubetriebspraxis / Hoffmann, Manfred ; Kuhlmann, Willy [Hrsg.].}, journal = {Beispiele f{\"u}r die Baubetriebspraxis / Hoffmann, Manfred ; Kuhlmann, Willy [Hrsg.].}, publisher = {Teubner}, address = {Wiesbaden}, isbn = {978-3-8351-0002-2}, pages = {63 -- 88}, year = {2006}, language = {de} } @book{OlkBauer1979, author = {Olk, Ulrich and Bauer, Hermann}, title = {Entwicklung von Kriterien f{\"u}r den optimalen Ablauf aller Teilvorg{\"a}nge des industrialisierten Bauens : Forschungsbericht / Hermann Bauer ; Ulrich Olk}, publisher = {Lehrstuhl f{\"u}r Baubetrieb und Baumaschinen, Univ.}, address = {Dortmund}, pages = {Getr. Z{\"a}hlung}, year = {1979}, language = {de} } @book{OlkBauer1983, author = {Olk, Ulrich and Bauer, Hermann}, title = {Sicherheitstechnische Anforderungen beim Ablauf von Hochbauvorhaben / H. Bauer ; U. Olk}, publisher = {Wirtschaftsverl. NW, Verl. f{\"u}r neue Wiss.}, address = {Bremerhaven}, isbn = {3-88314-324-3}, pages = {III, 102 S. : Ill., graph. Darst.}, year = {1983}, language = {de} } @masterthesis{Oltmanns2023, type = {Bachelor Thesis}, author = {Oltmanns, Maireni}, title = {Digitale Medien wollen gelernt sein : Kampagne f{\"u}r die "Medienscouts NRW" zur Kompetenzf{\"o}rderung}, publisher = {FH Aachen}, address = {Aachen}, school = {Fachhochschule Aachen}, pages = {41 Seiten}, year = {2023}, abstract = {,,Digitale Medien wollen gelernt sein" ist eine Kampagne f{\"u}r das Projekt Medienscouts. Hier werden im ersten Schritt interessierte Sch{\"u}ler:innen an weiterf{\"u}hrenden Schulen zu Medienexpert:innen ausgebildet. Im Zweiten geben sie ihr Wissen an ihre Mitsch{\"u}ler:innen weiter und fungieren in ihren Schulen als gleichaltrige Ansprechpartner:innen bei Fragen oder Problemen. Um weitere Sch{\"u}ler:innen f{\"u}r das Projekt zu werben, konzentriert sich die Kampagne auf eine altersgerechte Social Media-Pr{\"a}senz. Ebenso wie das Projekt gibt auch die Kampagne den teilnehmenden Medienscouts die Freiheit, ihre Erfahrungen und Tipps zu teilen. Hierzu ist ein praktikables Konzept entworfen worden, mit dem die Scouts fortlaufend ihre offiziellen Kan{\"a}le bespielen k{\"o}nnen.}, language = {de} } @article{OosterhuisOehlschlaegerBergetal.2011, author = {Oosterhuis, Koen and {\"O}hlschl{\"a}ger, Peter and Berg, Joost H. van den and Toebes, Mireille and Gomez, Raquel and Schumacher, Ton N. and Haanen, John B.}, title = {Preclinical development of highly effective and safe DNA vaccines directed against HPV 16 E6 and E7}, series = {International Journal of Cancer}, volume = {129}, journal = {International Journal of Cancer}, number = {2}, publisher = {Wiley}, address = {Weinheim}, isbn = {1097-0215}, pages = {397 -- 406}, year = {2011}, language = {en} } @article{OrtnerHauserSchmadereretal.2019, author = {Ortner, Marion and Hauser, Christine and Schmaderer, Christoph and Muggenthaler, Claudia and Hapfelmeier, Alexander and Sorg, Christian and Diehl-Schmid, Janine and Kurz, Alexander and F{\"o}rstl, Hans and Ikenberg, Benno and Kotliar, Konstantin and Holger, Poppert and Grimmer, Timo}, title = {Decreased vascular pulsatility in Alzheimer's disease dementia measured by transcranial color-coded duplex sonography}, series = {Neuropsychiatric disease and treatment}, journal = {Neuropsychiatric disease and treatment}, number = {15}, publisher = {Dove Medical Press}, address = {Albany, Auckland}, issn = {1178-2021}, doi = {10.2147/NDT.S225754}, pages = {3487 -- 3499}, year = {2019}, abstract = {Purpose: Impaired paravascular drainage of β-Amyloid (Aβ) has been proposed as a contributing cause for sporadic Alzheimer's disease (AD), as decreased cerebral blood vessel pulsatility and subsequently reduced propulsion in this pathway could lead to the accumulation and deposition of Aβ in the brain. Therefore, we hypothesized that there is an increased impairment in pulsatility across AD spectrum. Patients and Methods: Using transcranial color-coded duplex sonography (TCCS) the resistance and pulsatility index (RI; PI) of the middle cerebral artery (MCA) in healthy controls (HC, n=14) and patients with AD dementia (ADD, n=12) were measured. In a second step, we extended the sample by adding patients with mild cognitive impairment (MCI) stratified by the presence (MCI-AD, n=8) or absence of biomarkers (MCI-nonAD, n=8) indicative for underlying AD pathology, and compared RI and PI across the groups. To control for atherosclerosis as a confounder, we measured the arteriolar-venular-ratio of retinal vessels. Results: Left and right RI (p=0.020; p=0.027) and left PI (p=0.034) differed between HC and ADD controlled for atherosclerosis with AUCs of 0.776, 0.763, and 0.718, respectively. The RI and PI of MCI-AD tended towards ADD, of MCI-nonAD towards HC, respectively. RIs and PIs were associated with disease severity (p=0.010, p=0.023). Conclusion: Our results strengthen the hypothesis that impaired pulsatility could cause impaired amyloid clearance from the brain and thereby might contribute to the development of AD. However, further studies considering other factors possibly influencing amyloid clearance as well as larger sample sizes are needed.}, language = {en} } @article{OrzadaMaderwaldPoseretal.2012, author = {Orzada, S. and Maderwald, S. and Poser, B. A. and Johst, S. and Kannengiesser, S. and Ladd, M. E. and Bitz, Andreas}, title = {Time-interleaved acquisition of modes: an analysis of SAR and image contrast implications}, series = {Magnetic Resonance in Medicine}, volume = {67}, journal = {Magnetic Resonance in Medicine}, number = {4}, publisher = {Wiley-Liss}, address = {New York}, issn = {1522-2594}, doi = {10.1002/mrm.23081}, pages = {1033 -- 1041}, year = {2012}, abstract = {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.}, language = {en} } @article{OrzadaBitzJohstetal.2017, author = {Orzada, Stephan and Bitz, Andreas and Johst, S{\"o}ren and Gratz, Marcel and V{\"o}lker, Maximilian N. and Kraff, Oliver and Abuelhaija, Ashraf and Fiedler, Thomas M. and Solbach, Klaus and Quick, Harald H. and Ladd, Mark E.}, title = {Analysis of an integrated 8-Channel Tx/Rx body array for use as a body coil in 7-Tesla MRI}, series = {Frontiers in Physics}, volume = {5}, journal = {Frontiers in Physics}, number = {Jun}, issn = {2296-424X}, doi = {10.3389/fphy.2017.00017}, year = {2017}, language = {en} } @article{OrzadaBitzSchaeferetal.2011, author = {Orzada, Stephan and Bitz, Andreas and Sch{\"a}fer, Lena C. and Ladd, Susanne C. and Ladd, Mark E. and Maderwald, Stefan}, title = {Open design eight-channel transmit/receive coil for high-resolution and real-time ankle imaging at 7 T}, series = {Medical Physics}, volume = {38}, journal = {Medical Physics}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {2473-4209}, doi = {10.1118/1.3553399}, pages = {1162 -- 1167}, year = {2011}, abstract = {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.}, language = {en} } @article{OrzadaFiedlerBitzetal.2020, author = {Orzada, Stephan and Fiedler, Thomas M. and Bitz, Andreas and Ladd, Mark E. and Quick, Harald H.}, title = {Local SAR compression with overestimation control to reduce maximum relative SAR overestimation and improve multi-channel RF array performance}, series = {Magnetic Resonance Materials in Physics, Biology and Medicine}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, number = {34 (2021)}, publisher = {Springer}, address = {Heidelberg}, isbn = {1352-8661}, doi = {10.1007/s10334-020-00890-0}, pages = {153 -- 164}, year = {2020}, abstract = {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.}, language = {en} } @article{OrzadaJohstMaderwaldetal.2013, author = {Orzada, Stephan and Johst, S{\"o}ren and Maderwald, Stefan and Bitz, Andreas and Solbach, Klaus and Ladd, Mark E.}, title = {Mitigation of B1(+) inhomogeneity on single-channel transmit systems with TIAMO}, series = {Magnetic Resonance in Medicine}, volume = {70}, journal = {Magnetic Resonance in Medicine}, number = {1}, publisher = {Wiley}, address = {Weinheim}, issn = {1522-2594}, doi = {10.1002/mrm.24453}, pages = {290 -- 294}, year = {2013}, language = {en} } @article{OrzadaLaddBitz2016, author = {Orzada, Stephan and Ladd, Mark E. and Bitz, Andreas}, title = {A method to approximate maximum local SAR in multichannel transmit MR systems without transmit phase information}, series = {Magnetic Resonance in Medicine}, volume = {78}, journal = {Magnetic Resonance in Medicine}, number = {2}, publisher = {International Society for Magnetic Resonance in Medicine}, issn = {1522-2594}, doi = {10.1002/mrm.26398}, pages = {805 -- 811}, year = {2016}, abstract = {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}, language = {en} } @article{OrzadaMaderwaldPoseretal.2010, author = {Orzada, Stephan and Maderwald, Stefan and Poser, Benedikt Andreas and Bitz, Andreas and Quick, Harald H. and Ladd, Mark E.}, title = {RF excitation using time interleaved acquisition of modes (TIAMO) to address B1 inhomogeneity in high-field MRI}, series = {Magnetic Resonance in Medicine}, volume = {64}, journal = {Magnetic Resonance in Medicine}, number = {2}, publisher = {Wiley-Liss}, address = {New York}, issn = {1522-2594}, doi = {10.1002/mrm.22527}, pages = {327 -- 333}, year = {2010}, abstract = {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.}, language = {en} } @article{OrzadaSolbachGratzetal.2019, author = {Orzada, Stephan and Solbach, Klaus and Gratz, Marcel and Brunheim, Sascha and Fiedler, Thomas M. and Johst, S{\"o}ren and Bitz, Andreas and Shooshtary, Samaneh and Abuelhaija, Ashraf and Voelker, Maximilian N. and Rietsch, Stefan H. G. and Kraff, Oliver and Maderwald, Stefan and Fl{\"o}ser, Martina and Oehmingen, Mark and Quick, Harald H. and Ladd, Mark E.}, title = {A 32-channel parallel transmit system add-on for 7T MRI}, series = {Plos one}, journal = {Plos one}, doi = {10.1371/journal.pone.0222452}, year = {2019}, language = {en} }