@phdthesis{Gold2023,
  author    = {Gold, Lukas},
  title     = {Methods for the state estimation of lithium-ion batteries},
  doi       = {10.25972/OPUS-30618},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-306180},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {This work introduced the reader to all relevant fields to tap into an ultrasound-based state of charge estimation and provides a blueprint for the procedure to achieve and test the fundamentals of such an approach. It spanned from an in-depth electrochemical characterization of the studied battery cells over establishing the measurement technique, digital processing of ultrasonic transmission signals, and characterization of the SoC dependent property changes of those signals to a proof of concept of an ultrasound-based state of charge estimation. The State of the art \& theoretical background chapter focused on the battery section on the mechanical property changes of lithium-ion batteries during operation. The components and the processes involved to manufacture a battery cell were described to establish the fundamentals for later interrogation. A comprehensive summary of methods for state estimation was given and an emphasis was laid on mechanical methods, including a critical review of the most recent research on ultrasound-based state estimation. Afterward, the fundamentals of ultrasonic non-destructive evaluation were introduced, starting with the sound propagation modes in isotropic boundary-free media, followed by the introduction of boundaries and non-isotropic structure to finally approach the class of fluid-saturated porous media, which batteries can be counted to. As the processing of the ultrasonic signals transmitted through lithium-ion battery cells with the aim of feature extraction was one of the main goals of this work, the fundamentals of digital signal processing and methods for the time of flight estimation were reviewed and compared in a separate section. All available information on the interrogated battery cell and the instrumentation was collected in the Experimental methods \& instrumentation chapter, including a detailed step-by-step manual of the process developed in this work to create and attach a sensor stack for ultrasonic interrogation based on low-cost off-the-shelf piezo elements. The Results \& discussion chapter opened with an in-depth electrochemical and post-mortem interrogation to reverse engineer the battery cell design and its internal structure. The combination of inductively coupled plasma-optical emission spectrometry and incremental capacity analysis applied to three-electrode lab cells, constructed from the studied battery cell's materials, allowed to identify the SoC ranges in which phase transitions and staging occur and thereby directly links changes in the ultrasonic signal properties with the state of the active materials, which makes this work stand out among other studies on ultrasound-based state estimation. Additional dilatometer experiments were able to prove that the measured effect in ultrasonic time of flight cannot originate from the thickness increase of the battery cells alone, as this thickness increase is smaller and in opposite direction to the change in time of flight. Therefore, changes in elastic modulus and density have to be responsible for the observed effect. The construction of the sensor stack from off-the-shelf piezo elements, its electromagnetic shielding, and attachment to both sides of the battery cells was treated in a subsequent section. Experiments verified the necessity of shielding and its negligible influence on the ultrasonic signals. A hypothesis describing the metal layer in the pouch foil to be the transport medium of an electrical coupling/distortion between sending and receiving sensor was formulated and tested. Impedance spectroscopy was shown to be a useful tool to characterize the resonant behavior of piezo elements and ensure the mechanical coupling of such to the surface of the battery cells. The excitation of the piezo elements by a raised cosine (RCn) waveform with varied center frequency in the range of 50 kHz to 250 kHz was studied in the frequency domain and the influence of the resonant behavior, as identified prior by impedance spectroscopy, on waveform and frequency content was evaluated to be uncritical. Therefore, the forced oscillation produced by this excitation was assumed to be mechanically coupled as ultrasonic waves into the battery cells. The ultrasonic waves transmitted through the battery cell were recorded by piezo elements on the opposing side. A first inspection of the raw, unprocessed signals identified the transmission of two main wave packages and allowed the identification of two major trends: the time of flight of ultrasonic wave packages decreases with the center frequency of the RCn waveform, and with state of charge. These trends were to be assessed further in the subsequent sections. Therefore, methods for the extraction of features (properties) from the ultrasonic signals were established, compared, and tested in a dedicated section. Several simple and advanced thresholding methods were compared with envelope-based and cross-correlation methods to estimate the time of flight (ToF). It was demonstrated that the envelope-based method yields the most robust estimate for the first and second wave package. This finding is in accordance with the literature stating that an envelope-based method is best suited for dispersive, absorptive media [204], to which lithium-ion batteries are counted. Respective trends were already suggested by the heatmap plots of the raw signals vs. RCn frequency and SoC. To enable such a robust estimate, an FIR filter had to be designed to preprocess the transmitted signals and thereby attenuate frequency components that verifiably lead to a distorted shape of the envelope. With a robust ToF estimation method selected, the characterization of the signal properties ToF and transmitted energy content (EC) was performed in-depth. A study of cycle-to-cycle variations unveiled that the signal properties are affected by a long rest period and the associated relaxation of the multi-particle system "battery cell" to equilibrium. In detail, during cycling, the signal properties don't reach the same value at a given SoC in two subsequent cycles if the first of the two cycles follows a long rest period. In accordance with the literature, a break-in period, making up for more than ten cycles post-formation, was observed. During this break-in period, the mechanical properties of the system are said to change until a steady state is reached [25]. Experiments at different C-rate showed that ultrasonic signal properties can sense the non-equilibrium state of a battery cell, characterized by an increasing area between charge and discharge curve of the respective signal property vs. SoC plot. This non-equilibrium state relaxes in the rest period following the discharge after the cut-off voltage is reached. The relaxation in the rest period following the charge is much smaller and shows little C-rate dependency as the state is prepared by constant voltage charging at the end of charge voltage. For a purely statistical SoC estimation approach, as employed in this work, where only instantaneous measurements are taken into account and the historic course of the measurement is not utilized as a source of information, the presence of hysteresis and relaxation leads to a reduced estimation accuracy. Future research should address this issue or even utilize the relaxation to improve the estimation accuracy, by incorporating historic information, e.g., by using the derivative of a signal property as an additional feature. The signal properties were then tested for their correlation with SoC as a function of RCn frequency. This allowed identifying trends in the behavior of the signal properties as a function of RCn frequency and C-rate in a condensed fashion and thereby enabled to predict the frequency range, about 50 kHz to 125 kHz, in which the course of the signal properties is best suited for SoC estimation. The final section provided a proof of concept of the ultrasound-based SoC estimation, by applying a support vector regression (SVR) to before thoroughly studied ultrasonic signal properties, as well as current and battery cell voltage. The included case study was split into different parts that assessed the ability of an SVR to estimate the SoC in a variety of scenarios. Seven battery cells, prepared with sensor stacks attached to both faces, were used to generate 14 datasets. First, a comparison of self-tests, where a portion of a dataset is used for training and another for testing, and cross-tests, which use the dataset of one cell for training and the dataset of another for testing, was performed. A root mean square error (RMSE) of 3.9\% to 4.8\% SoC and 3.6\% to 10.0\% SoC was achieved, respectively. In general, it was observed that the SVR is prone to overestimation at low SoCs and underestimation at high SoCs, which was attributed to the pronounced hysteresis and relaxation of the ultrasonic signal properties in this SoC ranges. The fact that higher accuracy is achieved, if the exact cell is known to the model, indicates that a variation between cells exists. This variation between cells can originate from differences in mechanical properties as a result of production variations or from differences in manual sensor placement, mechanical coupling, or resonant behavior of the ultrasonic sensors. To mitigate the effect of the cell-to-cell variations, a test was performed, where the datasets of six out of the seven cells were combined as training data, and the dataset of the seventh cell was used for testing. This reduced the spread of the RMSE from (3.6 - 10.0)\% SoC to (5.9 - 8.5)\% SoC, respectively, once again stating that a databased approach for state estimation becomes more reliable with a large data basis. Utilizing self-tests on seven datasets, the effect of additional features on the state estimation result was tested. The involvement of an additional feature did not necessarily improve the estimation accuracy, but it was shown that a combination of ultrasonic and electrical features is superior to the training with these features alone. To test the ability of the model to estimate the SoC in unknown cycling conditions, a test was performed where the C-rate of the test dataset was not included in the training data. The result suggests that for practical applications it might be sufficient to perform training with the boundary of the use cases in a controlled laboratory environment to handle the estimation in a broad spectrum of use cases. In comparison with literature, this study stands out by utilizing and modifying off-the-shelf piezo elements to equip state-of-the-art lithium-ion battery cells with ultrasonic sensors, employing a range of center frequencies for the waveform, transmitted through the battery cell, instead of a fixed frequency and by allowing the SVR to choose the frequency that yields the best result. The characterization of the ultrasonic signal properties as a function of RCn frequency and SoC and the assignment of characteristic changes in the signal properties to electrochemical processes, such as phase transitions and staging, makes this work unique. By studying a range of use cases, it was demonstrated that an improved SoC estimation accuracy can be achieved with the aid of ultrasonic measurements - thanks to the correlation of the mechanical properties of the battery cells with the SoC.},
  subject      = {Lithium-Ionen-Akkumulator},
  language  = {en}
}
@phdthesis{Schulz2023,
  author    = {Schulz, Ellina},
  title     = {Lokale Ultraschall-vermittelte Zytostatika-Applikation zur Behandlung von Hirntumoren},
  doi       = {10.25972/OPUS-32016},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320168},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Glioblastoma (GBM) sind b{\"o}sartige hirneigene Tumore, deren schlechte Prognose einer innovativen Therapie bedarf. Aus diesem Grund wurde ein neuer Therapieansatz entwickelt, der auf einer lokalen Ultraschall-vermittelten Zytostatika Applikation beruht. Hierf{\"u}r wurden stabile Microbubbles (MB) bestehend aus Phospholipiden synthetisiert. Es konnte gezeigt werden, dass MB als auch fokussierter Ultraschall niedriger Intensit{\"a}t (LIFU) keinen negativen Einfluss auf GBM-Zellen hat. MB hingegen konnten mittels LIFU destruiert werden, wodurch das in den MB eingeschlossene Chemotherapeutikum freigesetzt werden kann. Es wurden verschiedene Platin(II)- und Palladium(II)-Komplexe auf GBM Zellen getestet. Zur Beladung der MB wurde Doxorubicin (Dox) verwendet. Es konnte eine Beladungseffizienz der MB mit Dox von 52 \% erreicht werden, auch eine Aufreinigung dieser mittel Ionenaustausch-Chromatographie und Dialyse war erfolgreich. Die Austestung der mit Dox beladenen MB (MBDox) erfolgte auf GBM-Zellen in 2D- und 3D-Zelkulturmodellen. Dabei zeigte sich, dass die Behandlung mit MBDox und LIFU f{\"u}r 48 h eine zytotoxische Wirkung hatte, die sich signifikant von der Behandlung mit MBDox ohne LIFU unterschied. Zur Austestung der MBDox in 3D-Zellkulturmodellen wurden zwei Scaffold-Systeme eingesetzt. Es zeigte sich in den Versuchen, dass MBDox mit LIFU im Vergleich zu MBDox ohne LIFU Applikation einen zytotoxischen Effekt auf GBM-Zellen haben. Somit konnte die Wirksamkeit der Zytostatika Applikation mittels MB und LIFU in 2D- und 3D-Zellkulturmodellen erfolgreich etabliert werden. Als weiterer Schritt wurden zwei 3D in vitro Modelle erarbeitet. Dabei wurden zun{\"a}chst organotypische hippocampale Slice Kulturen (organotypic hippocampal brain slice cultures, OHSC) aus der Maus hergestellt und anschließend mit fluoreszent-markierten Mikrotumoren aus GBM-Zelllinien, Prim{\"a}rzellen (PZ) und aus Patienten generierten GBM-Organoiden hergestellt. Diese GBM-Modelle wurden mit Tumor Treating Fields (TTFields) behandelt. Dabei war eine Abnahme der Tumorgr{\"o}ße von Mikrotumoren aus GBM-Zellen und PZ unter TTFields-Behandlung f{\"u}r 72 h messbar. Als weiteres in vitro Modell wurden humane Tumorschnitte aus intraoperativ entferntem GBM-Patientenmaterial hergestellt. Die Schnitte wiesen ein heterogenes Ansprechen nach 72 h TTFields-Applikation auf. Dies spiegelt die Heterogenit{\"a}t des GBM sehr gut wider und best{\"a}rkt die Eignung des Modelles zur Untersuchung von neuen Therapieans{\"a}tzen zur Behandlung von GBM.},
  subject      = {Glioblastom},
  language  = {de}
}
@phdthesis{Forster2023,
  author    = {Forster, Andr{\´e}},
  title     = {Targeting Temporally Stable Vulnerability Factors in the Prediction of Long-Term Courses of Depression: Diagnostic Considerations and Therapeutic Protocols Based on Transcranial Ultrasonic Neuromodulation of Endophenotypes},
  doi       = {10.25972/OPUS-27906},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-279065},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Depressive disorders represent one of the main sources for the loss of healthy years of life. One of the reasons for this circumstance is the recurrent course of these disorders, which can be interrupted by current therapeutic approaches, especially in the shortterm, but seem to be maintained at least in part in the long-term. Subsequently, on one hand, this thesis deals with methodological measurement issues in the longitudinal prediction of depressive courses. On the other hand, it addresses two currently discussed neuroscience-based treatment approaches, which are investigated experimentally in a basic-psychological manner and reviewed in the light of their potential to translate results to the application in patient care. These two approaches each address potential mechanisms that may negatively impact long-term disease trajectories: First, stable endophenotypes for vulnerability factors that could regain control over the organism and reactivate maladaptive experiences, or behaviors with increasing temporal distance from therapeutic methods are focused on. In the studies presented, these were influenced by a recently rediscovered method of neuromodulation (transcranial low-intensity focused ultrasound) which is discussed in light of its unique capability to address even deepest, subcortical regions at a high spatial resolution. Lastly, as a second approach, an experimental design for the use of reconsolidation interference is presented, which could provide a first insight into the applicability of corresponding protocols in the field of depressive disorders and thus contribute to the modification, instead of inhibition, of already mentioned endophenotypes. In sum, methodological considerations for monitoring and predicting long-term courses of depression are deducted before two approaches are discussed that could potentially exert positive influences on the recurrent nature of depressive symptoms on their own, in combination with each other, or as augmentation for existing therapeutic procedures.},
  subject      = {Depression},
  language  = {en}
}
@phdthesis{Koeberle2021,
  author    = {K{\"o}berle, Philipp},
  title     = {High-resolution ultrasound for the identification of pathological patterns in patients with polyneuropathies and amyotrophic lateral sclerosis},
  doi       = {10.25972/OPUS-24580},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-245800},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Neuropathies are a group of potentially treatable diseases with an often disabling and restricting course. Amyotrophic lateral sclerosis (ALS) is a lethal disease without causal treatment possibilities. The objective of this study was to examine the diagnostic utility of HRUS for the differentiation of subtypes of axonal and demyelinating neuropathies and to investigate its utility for the sonological differentiation of ALS. The hypothetical statement that neuropathy causes enlargement of peripheral nerves compared to healthy controls proved to be right, but the adjunctive assumption that ALS does not cause enlargement of peripheral nerves proved to be wrong - in patients with ALS slight enlargement of peripheral nerves was visible as well. The statement that nerve enlargement can be detected by measurement of the cross-sectional area (CSA) and the longitudinal diameter (LD) with comparable results proved to be right, but the enlargement was slightly less present by measurement of the LD. The statement that axonal and demyelinating neuropathies show distinct patterns of nerve enlargement must be answered differentiated: The comparison between axonal and demyelinating neuropathies showed a stronger nerve enlargement in patients with demyelinating neuropathies than in patients with axonal neuropathies at proximal nerve segments of upper extremities. In the comparison of diagnose-defined subgroups of inflammatory demyelinating neuropathies a respective specific pattern of nerve enlargement was visible. However, remarkable in this context was the strong nerve enlargement found in patients with NSVN, which is classified as an axonal neuropathy. Stratification for specific findings in nerve biopsy did not lead to constructive differences in comparison between the different groups. To sum up, HRUS showed to provide a useful contribution in the diagnostic process of neuropathies and ALS but needs to be integrated in a multimodal diagnostic approach.},
  subject      = {Polyneuropathie},
  language  = {en}
}
@phdthesis{Fischer2021,
  author    = {Fischer, Gregor},
  title     = {Navigations- und Ultraschallgest{\"u}tzte Punktion der Leistenarterie beim transfemoralen Aortenklappenersatz},
  doi       = {10.25972/OPUS-23158},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231586},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Transcatheter aortic valve replacement (TAVR) is an established procedure for treatment of aortic stenosis. In transfemoral TAVR local vascular complications at the puncture site are still an important issue and responsible for the majority of complications. To ensure safe puncture in a non-calcified vessel segment a new navigation technique with ultrasound guidance has been developed. We compared 67 consecutive patients undergoing TAVR using our new approach with 67 patients with fluoroscopic punction.},
  subject      = {Aortenklappenersatz},
  language  = {de}
}
@phdthesis{MawambaKemo2020,
  author    = {Mawamba Kemo, Viviane},
  title     = {Beladung von Microbubbles mit Platin(II)- oder Palladium(II)-Komplexen und Freisetzung unter Einwirkung von Ultraschall zur Behandlung von Glioblastomen},
  doi       = {10.25972/OPUS-21616},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-216165},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2020},
  abstract  = {Metall-basierte Antitumorwirkstoffe wie Cisplatin, Carboplatin und Oxaliplatin sind weltweit f{\"u}r die Behandlung verschiedener Krebsarten zugelassen. Resistenzbildung, starke Nebenwirkungen und ein eingeschr{\"a}nktes Spektrum responsiver Tumoren schr{\"a}nken jedoch ihren Anwendungsbereich ein. Daher ist die Suche nach neuen Platinverbindungen mit verbesserten Eigenschaften sowie Antitumor-aktiven Metallkomplexen anderer Metalle ein aktuelles Forschungsthema. Durch die Einbettung der Wirkstoffe in entsprechende Tr{\"a}germaterialien und eine Freisetzung mit pr{\"a}ziser zeitlicher und r{\"a}umlicher Kontrolle sollten sich zudem die Nebenwirkungen deutlich reduzieren lassen. Im Rahmen dieser Doktorarbeit wurde daher eine Serie von quadratisch-planaren Platin(II)- und Palladium(II)-Komplexen mit N^N^S-Chelatliganden auf der Basis von N-Phenyl-2-(pyridin-2-ylmethylen)hydrazin-1-carbothioamid und N-Phenyl-2-(chinolin-2-ylmethylen)hydrazin-1-carbothioamid synthetisiert, die mit l{\"a}ngeren Alkylketten funktionalisiert wurden, um eine hohe Affinit{\"a}t f{\"u}r Lipid-basierte Microbubbles als Tr{\"a}ger zu erreichen, aus denen die Metallkomplexe dann unter Einwirkung von Ultraschall freigesetzt werden sollten. Es wurden drei verschiedene Ligandenfamilien ausgehend von der Grundstruktur L = R1-CR2=N-NH-C(S)-NH-R3 synthetisiert, wobei R1 = 2-Pyridyl oder 2-Chinolinyl, R2 = H, CH3, C8H17 oder C10H21 und R3 = CH3 oder C6H5 gew{\"a}hlt wurden. Die Umsetzung der Liganden mit Kaliumtetrachloridoplatinat(II), Natriumtetrachloridopalladat(II) oder [PdCl2(cod)] mit cod = 1,5-Cyclooctadien f{\"u}hrte zu neutralen N^N^S-Komplexen [MCl(L)] mit M = Pd, Pt in allgemein guter Ausbeute. Die Kristallstruktur von [PtCl(L)] mit R1 = 2-Pyridyl, R2 = C10H21 und R3 = CH3 best{\"a}tigte zudem die quadratisch-planar Koordination des Metalls durch den N^N^S-koordinierten Liganden und ein Chlorid-Anion. Die Verbindungen mit R3 = CH3 zeigen im 195Pt NMR zwei Peaks, was auf das Vorliegen eines Isomerengemischs hindeutet, wobei die Daten vermuten lassen, dass neben der N^N^S-gebundenen Hauptspezies noch eine weitere mit N^N^N-koordiniertem Liganden und freier SH-Gruppe vorliegt. Solche Isomerengemische sind f{\"u}r biologischen Anwendungen ungeeignet, da die Isomere eine unterschiedliche Aktivit{\"a}t aufweisen k{\"o}nnen. Die anderen Platin(II)-Komplexe zeigen dagegen im 195Pt NMR nur einen Peak und sind somit f{\"u}r Cytotoxizit{\"a}tsstudien geeignet. Mit Hilfe des MTT-Assays wurden EC50-Werte an verschiedenen Gliablastom-Zellinien f{\"u}r zw{\"o}lf einheitliche Komplexe bestimmt. F{\"u}r die potentesten Verbindungen wurden EC50-Werte im unteren mikromolaren Bereich ermittelt (2-9 µM), so dass die Aktivit{\"a}t teilweise sogar die von Cisplatin als Referenzverbindung {\"u}bertraf. Insbesondere die Variation der aromatischen Oberfl{\"a}che in den Pyridyl- vs. Chinolinylverbindungen hatte jedoch keinen wesentlichen Einfluss auf die EC50-Werte. Zudem f{\"u}hrte eine Verl{\"a}ngerung der R2-Seitenkette bei den Palladium(II)-Verbindungen zu einer niedrigeren Aktivit{\"a}t. Die Verteilungskoeffizienten logP ergaben f{\"u}r alle Verbindungen recht {\"a}hnliche positive Werte, was die Lipophilie der Neutralkomplexe belegte. F{\"u}r eine weitere Strukturvariation wurden außerdem zwei Azido-Komplexe [M(N3)(L)] mit M = Pd, Pt in moderater Ausbeute synthetisiert. Diese wurden dann in einer „iClick"-Reaktion unter sehr milden Bedingungen mit Dimethylacetylendicarboxylat (DMAD) und 4,4,4-Trifluorobut-2-ins{\"a}ureethylester zu den Triazolat-Komplexen [M(triazolateR,R')(L)] umgesetzt. Durch 1H NMR- und 19F NMR-spektroskopische Untersuchungen wurden gezeigt, dass diese teilweise als Isomerengemische vorliegen, da das Triazolat entweder {\"u}ber das N1-, N2- oder N3-Stickstoffatom an das Metall gebunden sein kann. F{\"u}r eine ausgew{\"a}hlte Verbindung mit M = Pt und DMAD als Alkin wurde die Kinetik der „iClick"-Reaktion mit Hilfe der 1H NMR Spektroskopie untersucht. Die ermittelte Geschwindigkeitskonstante 2. Ordnung k2 = (1.82 ± 0.05).10-1 L mol-1 s 1 ist vergleichbar zum Beispiel der der etablierten strain-promoted azide-alkyne cycloaddition (SPAAC). F{\"u}r die Einbettung der lipophilen Metallkomplexe in ein Ultraschall-aktivierbares Tr{\"a}gersystem wurden aus Dipalmytoylphosphatidylcholin, 1,2-Dipalmitoyl-sn-glycero-3-phosphat, 1,2-Distearoyl-sn-glycero-3-phosphoethanolamin-N-methoxy(polyethylenglycol)-2000 Ammonium Salz und Komplexl{\"o}sung unter Zusatz von Octafluopropan gasgef{\"u}llte Microbubbles hergestellt. Stabilit{\"a}tsversuche zeigten, dass die Bl{\"a}schenzahl selbst unter Normalbedingungen innerhalb von 2 h um 50\% abnimmt. Daher sollten die Microbubbles vor jeder Verwendung t{\"a}glich frisch hergestellt und m{\"o}glichst unmittelbar danach verwendet werden. Ein unmittelbares Zerplatzen der Bl{\"a}schen wurde durch Behandlung mit Ultraschall bei 500 Hz erreicht. Die Viabilit{\"a}t der verwendeten GaMG-Zellen wudre unter diesen Bedingungen jedoch nicht beeintr{\"a}chtigt. Dennoch war die auf die Microbubbles geladene Platin-Konzentration zu niedrig, um mit dem MTT-Assay einen signifikanten Unterschied zwischen beladenen und unbeladenen Bl{\"a}schen zu erreichen, so dass hier in Zukunft noch weitere Optimierungen erforderlich sein werden.},
  subject      = {Glioblastom},
  language  = {de}
}
@phdthesis{Bach2017,
  author    = {Bach, Tobias},
  title     = {Electromechanical interactions in lithium-ion batteries: Aging effects and analytical use},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-153325},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {In the first part of his work, the causes for the sudden degradation of useable capacity of lithium-ion cells have been studied by means of complementary methods such as computed tomography, Post-Mortem studies and electrochemical analyses. The results obtained point unanimously to heterogeneous aging as a key-factor for the sudden degradation of cell capacity, which in turn is triggered by differences in local compression. At high states of health, the capacity fade rate is moderate but some areas of the graphite electrode degrade faster than others. Still, the localized changes are hardly noticeable on cell level due to averaging effects. Lithium plating occurs first in unevenly compressed areas, creating patterns visible to the human eye. As lithium plating leads to rapid consumption of active lithium, a sudden drop in capacity is observed on cell level. Lithium plating appears to spread out from the initial areas over the whole graphite electrode, quickly consuming the remaining useful lithium and active graphite. It can be hypothesized that a self-amplifying circle of reciprocal acceleration of local lithium loss and material loss causes rapid local degradation. Battery cell designers can improve cycle life by homogeneous pressure distribution in the cell and using negative active materials that are resilient to elevated discharge potentials such as improved carbons or lithium titanate. Also, a sufficiently oversized negative electrode and suitable electrolyte additives can help to avoid lithium plating. When packs are designed, care must be taken not to exert local pressure on parts of cells and to avoid both very high and low states of charge. In the second part of this dissertation the resilience of cylindrical and pouchbag cells to shocks and different vibrations was investigated. Stresses inflicted by vibration and shock tests according to the widely recognized UN38.3 transport test were compared to a long-time test that exposed cells to a 186 days long ordeal of sine sweep vibrations with a profile based on real-world applications. All cells passed visual and electric inspection performed by TU M{\"u}nchen after the vibration tests. Only cylindrical cells subjected to long-term vibrations in axial direction showed an increase in impedance and a loss of capacity that could be recuperated in part. The detailed analyses presented in this thesis gave more details on the damages inflicted by vibrations and shocks and revealed drastic damages in some cases. In cylindrical cells, only movement in axial direction caused damage. Long term vibrations were found to be especially detrimental. No damage whatsoever could be detected for pouch cells, regardless of the test protocol and the direction of movement. The extreme resilience of pouchbag cells shows that the electrode stack of lithium-ion cells is resistant to vibrations, and that damages are caused by design imperfections that can be improved at low cost. The findings of this work, and the general state of research show that it is most crucial to control the lithiation and thus potential of the graphite electrode. In the last part of this work, a new, direct method for charge estimation based on changing transmission is presented. A correlation between transmission of short ultrasonic pulses and state of charge is found. This new technology allows direct measurement of the state of charge. The method is demonstrated for batteries with different positive active materials, showing its versatility. As the observed changes can be traced to the lithiation of graphite, it can be determined without a reference electrode. Already at this early stage of development, the found correlations allow estimation of state of charge. The present hysteresis in the signal height of the slow wave, which is unneglectable especially during discharging at higher currents, will be subject to further investigation. The observed effects can be explained by effects on different length scales. Biot's theory explains the second wave's slowness based on the active material particles size in the range of 0.01 mm and electrolyte-filled pores. Lithiation of graphite changes the porosity of the electrode and thereby the velocity and wavelength of the impulse. When the wavelength approaches the length scale of the layers, 0.1 mm, scattering effects dampen the transmitted signal. Finally, the wavelength of the pulse should be shorter than the transducers diameter to obtain a homogeneous wave front. To conclude, the new method allows the control of each individual cell in a pack independent from the electrical connections of the cells. As the method shows great promise, further studies regarding factors such as long-term behavior, temperature and current rates should be conducted. In this thesis hysteresis was observed and a deeper understanding of the reasons behind it may allow further improvements of measurement precision.},
  subject      = {Lithium-Ionen-Akkumulator},
  language  = {en}
}
@phdthesis{Geppert2013,
  author    = {Geppert, Thomas},
  title     = {Systematische Analyse der Sichtbarkeit von Regionalan{\"a}sthesienadeln mittels Ultraschall - eine in vitro Studie},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137529},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {In einigen Punkten konnte diese Arbeit die Ergebnisse fr{\"u}herer Studien best{\"a}tigen. Einstellungs- und Nadelmodi (wenn auch mit unterschiedlicher Auspr{\"a}gung) haben einen Einfluss auf die verbesserte Sichtbarkeit der Regionalan{\"a}sthesienadeln im Ultraschall. Damit diese sonographisch besser erkannt werden, sollten sie in einem flacheren Winkel (30-45°) eingestochen werden. Gr{\"o}ßere Nadellumina haben einen Vorteil in der Sichtbarkeit im Ultraschall. Auch konnte gezeigt werden, dass der Nadelschliff einen Einfluss darauf hat, wie gut die An{\"a}sthesiekan{\"u}lenspitze sonographisch gesehen wird. Allein die (in der Arbeit untersuchten) Nadelbeschichtungs- Arten brachten keinen wesentlichen Effekt f{\"u}r die verbesserte Erkennbarkeit. Es war jedoch auffallend, dass die subjektiven und objektiven Resultate in einem relativ hohen Maße nicht {\"u}bereinstimmten. Gr{\"u}nde daf{\"u}r sehe ich v.a. im gew{\"a}hlten Verfahren der objektiven Untersuchung (mit der Bildbearbeitungssoftware muss die region of interest zielgenauer erfasst werden, um st{\"o}rende Umgebungseinfl{\"u}sse auszuschließen). Echogene Nadeloberfl{\"a}chen (auch wenn diese nicht Gegenstand der vorliegenden Untersuchung waren), weisen eine verbesserte Ultraschall-Reflexion auf. Sie werden dazu beitragen, dass die sichere Anwendung der USRA weiter zunimmt. Verbesserte Sonographieger{\"a}te, zus{\"a}tzliche Hilfsmittel (GPS-Unterst{\"u}tzung) und neueste Nadelentwicklungen versprechen einen wichtigen Fortschritt auf dem Gebiet der ultraschallunterst{\"u}tzten Regionalan{\"a}sthesie (USRA). Diese Weiterentwicklungen werden der USRA den Stellenwert als Gold-Standard in der Regionalan{\"a}sthesie sichern.},
  subject      = {Regionalan{\"a}sthesie},
  language  = {de}
}
@phdthesis{Krupinski2012,
  author    = {Krupinski, Tabea},
  title     = {Nachweis von morphologischen Ver{\"a}nderungen beim Nierenscreening von Fr{\"u}hgeborenen und deren klinische Relevanz},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-73915},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Die Sonographie ist f{\"u}r die Diagnosestellung der Nephrokalzinose Goldstandard. Gerade durch die technische Weiterentwicklung kommen aber immer wieder neue Herausforderungen auf den Untersucher zu. H{\"o}here Frequenzen und dadurch h{\"o}here Aufl{\"o}sungen der Bilder f{\"u}hren zu einer h{\"a}ufigeren Darstellung von Ver{\"a}nderungen, die es zu interpretieren gilt. So kommt es bei Nierenuntersuchungen Fr{\"u}hgeborener auff{\"a}llig oft zu einem Auftreten von Echogenit{\"a}tsanhebungen, die meist als Nephrokalzinose diagnostiziert werden. Die vorliegende Studie sollte durch Messungen von Helligkeit und Gr{\"o}ßenverh{\"a}ltnissen, sowie durch Auswertung bestimmter Laborparameter weitere und unabh{\"a}ngigere Kriterien zur Diagnosestellung der Nephrokalzinose finden.},
  subject      = {Ultraschall},
  language  = {de}
}
@phdthesis{Schmid2012,
  author    = {Schmid, Benedikt},
  title     = {Relation between cerebral arterio-venous transit time and neuropsychological performance in patients with vascular dementia},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-71234},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Dementia, or any form of degenerative cognitive decline, is one of the major problems in present, and even more will be in future medicine. With Alzheimer's disease (AD) being the most prevalent, Vascular Dementia is the second most entity of dementing processes in the elderly. As diagnostic criteria are still imprecise and in many cases do not embrace early stages of the disease, recent studies have proposed more detailed classifications of the newly created condition Vascular Cognitive Impairment (VCI). Of all conditions subsumed under this term, subcortical small-vessel alterations are the most common cause for cognitive decline. The diagnosis of dementia / cognitive impairment is presently often made in late stages of the disease, when therapeutical options are poor. Thus, early detection of changes of the subcortical small vessels is desirable, when there is still time to identify and aggressively treat risk factors and underlying conditions like diabetes, hyper- or hypotension, and hyperlipidemia. This study aimed to evaluate whether cTT correlates to cognitive dysfunction, i.e. if cTT is fit as an early diagnostic tool for VCI. The study cohort included 38 patients from the Neurological Clinic of the W{\"u}rzburg University hospital admitted due to diagnoses other than dementia or stroke. As a result of this study it turned out that cTT is certainly capable of fulfilling the task to easily and effectively detect and evaluate possible microvascular lesions of the brain with respect to the actual clinical relevance for the patient. When compared to the other proposed diagnostic tools, neuropsychological testing and MRI, the advantages of cTT are obvious: its measurement is a low-cost and quick procedure which would spare both patients and examiners a long neuropsychological exam or complement it. cTT is safe to assess as the only possible risks derive from the use of the contrast agent, which are rare and easily manageable. It has also proven to be more accurate in showing the extent of cognitive impairment than MRI. Finally, it is widely available. The only prerequisite is an ultrasound machine capable of transcranial color-coded duplex sonography. No cost-intensive procedures like MRI are needed. So, with neuropsychological testing remaining the gold standard, cTT here proved to be a reliable alternative which is more time- and cost-effective than MRI.},
  subject      = {Demenz},
  language  = {en}
}