Ultrasound medical imaging using 2d viscoacoustic full-waveform inversion = Medizinische Bildgebung mit Ultraschall unter Nutzung der 2d viskoakustischen Wellenfeldinversion

In dieser Arbeit führe ich eine ausführliche Literaturrecherche bezüglich der Brustbildgebung mit Ultraschall durch, wobei der Schwerpunkt auf bisherigen Anwendungen der Wellenfeldinversion (WFI) in diesem Forschungsgebiet liegt, untersuche das Potential der zweidimensionalen viskoakustischen WFI mit Hilfe von Rekonstruktionstests mit einem anatomiegetreuen numerischen Brustmodell unter optimalen Bedingungen und prüfe ob sich Datensätze, welche mit dem KIT 3D USCT II, dem ersten automatisierten Brustultraschallsystem mit einer vollständig dreidimensionalen Aufnahmegeometrie, aufgenommen wurden, mit dreidimensionaler WFI ausgewertet werden können. Die synthetischen Tests zeigen, dass die Schallgeschwindigkeit und Dämpfung mit hoher Genauigkeit rekonstruiert werden können, auch wenn niedrige Frequenzen genutzt werden. Die Nutzung niedriger Frequenzen ist in zweierlei Hinsicht von Vorteil, da diese eine hohe Stabilität der Inversion gewährleistet und gleichzeitig den nötigen Rechenaufwand reduziert. Die Durchführbarkeitsstudie befasst sich mit mehreren Herausforderungen, welchen man sich bei der Anwendung der dreidimensionalen WFI stellen muss, wie zum Beispiel die Berücksichtigung der Abstrahl- und Empfangscharakteristik der verwendeten Ultraschallsonden und Bewegungen der Brust während der Messungen. Es sind viel zu wenige Empfänger installiert, weshalb der räumliche Alias-Effekt Artefakte in den Gradienten hervorruft und nur eine sehr geringe Auflösung erreicht werden kann. Ich komme zu dem Ergebnis, dass eine Anwendung der dreidimensionalen WFI auf Daten des KIT 3D USCT II den extrem hohen Rechenaufwand nicht wert ist, da bei einer so stark begrenzten Auflösung das Potenzial der WFI nicht ausgeschöpft werden würde

Controlling the Young’s modulus of a ß-type Ti-Nb alloy via strong texturing by LPBF

The ß-type Ti-42Nb alloy was processed by laser powder bed fusion (LPBF) with an infrared top hat laser configuration aiming to control the Young’s modulus by creating an adapted crystallographic texture. Utilizing a top hat laser, a microstructure with a strong 〈0 0 1〉 texture parallel to the building direction and highly elongated grains was generated. This microstructure results in a strong anisotropy of the Young’s modulus that was modeled based on the single crystal elastic tensor and the experimental texture data. Tensile tests along selected loading directions were conducted to study the mechanical anisotropy and showed a good correlation with the modeled data. A Young’s modulus as low as 44 GPa was measured parallel to the building direction, which corresponds to a significant reduction of over 30% compared to the Young’s modulus of the Gaussian reference samples (67–69 GPa). At the same time a high 0.2% yield strength of 674 MPa was retained. The results reveal the high potential of LPBF processing utilizing a top hat laser configuration to fabricate patient-specific implants with an adapted low Young’s modulus along the main loading direction and a tailored mechanical biofunctionality

A novel adenovirus of Western lowland gorillas (Gorilla gorilla gorilla)

Adenoviruses (AdV) broadly infect vertebrate hosts including a variety of primates. We identified a novel AdV in the feces of captive gorillas by isolation in cell culture, electron microscopy and PCR. From the supernatants of infected cultures we amplified DNA polymerase (DPOL), preterminal protein (pTP) and hexon gene sequences with generic pan primate AdV PCR assays. The sequences in-between were amplified by long-distance PCRs of 2 - 10 kb length, resulting in a final sequence of 15.6 kb. Phylogenetic analysis placed the novel gorilla AdV into a cluster of primate AdVs belonging to the species Human adenovirus B (HAdV-B). Depending on the analyzed gene, its position within the cluster was variable. To further elucidate its origin, feces samples of wild gorillas were analyzed. AdV hexon sequences were detected which are indicative for three distinct and novel gorilla HAdV-B viruses, among them a virus nearly identical to the novel AdV isolated from captive gorillas. This shows that the discovered virus is a member of a group of HAdV-B viruses that naturally infect gorillas. The mixed phylogenetic clusters of gorilla, chimpanzee, bonobo and human AdVs within the HAdV-B species indicate that host switches may have been a component of the evolution of human and non-human primate HAdV-B viruses

Acid Sphingomyelinase Deficiency Ameliorates Farber Disease

Farber disease is a rare lysosomal storage disorder resulting from acid ceramidase deficiency and subsequent ceramide accumulation. No treatments for Farber disease are clinically available, and affected patients have a severely shortened lifespan. We have recently reported a novel acid ceramidase deficiency model that mirrors the human disease closely. Acid sphingomyelinase is the enzyme that generates ceramide upstream of acid ceramidase in the lysosomes. Using our acid ceramidase deficiency model, we tested if acid sphingomyelinase could be a potential novel therapeutic target for the treatment of Farber disease. A number of functional acid sphingomyelinase inhibitors are clinically available and have been used for decades to treat major depression. Using these as a therapeutic for Farber disease, thus, has the potential to improve central nervous symptoms of the disease as well, something all other treatment options for Farber disease can’t achieve so far. As a proof-of-concept study, we first cross-bred acid ceramidase deficient mice with acid sphingomyelinase deficient mice in order to prevent ceramide accumulation. Double-deficient mice had reduced ceramide accumulation, fewer disease manifestations, and prolonged survival. We next targeted acid sphingomyelinase pharmacologically, to test if these findings would translate to a setting with clinical applicability. Surprisingly, the treatment of acid ceramidase deficient mice with the acid sphingomyelinase inhibitor amitriptyline was toxic to acid ceramidase deficient mice and killed them within a few days of treatment. In conclusion, our study provides the first proof-of-concept that acid sphingomyelinase could be a potential new therapeutic target for Farber disease to reduce disease manifestations and prolong survival. However, we also identified previously unknown toxicity of the functional acid sphingomyelinase inhibitor amitriptyline in the context of Farber disease, strongly cautioning against the use of this substance class for Farber disease patients

Corrosion studies on Fe-30Mn-1C alloy in chloride-containing solutions with view to biomedical application

Austenitic Fe-30Mn-1C (FeMnC) is a prospective biodegradable implant material combining high mechanical integrity with adequate corrosion rates. The fast solidified TWIP alloy, its constituents and 316L stainless steel were electrochemically analysed in various electrolytes at 37 °C under laminar flow. Potentiodynamic polarization tests were conducted in Tris-buffered simulated body fluid (SBF), in Tris-buffered saline (TBS) and in 150-0.15 mM NaCl solutions (pH 7.6, 10, 5, 2) to study initial corrosion stages. Active dissolution of FeMnC is revealed in all electrolytes and is discussed on basis of the Fe and Mn behaviour plus is compared to that of 316L. The role of Tris (Tris(hydroxymethyl)aminomethane) as organic buffer for SBFs is critically assessed, particularly with view to the sensitivity of Fe. SEM studies of FeMnC corroded in NaCl revealed preferential dissolution along Mn-rich grain boundary regions. Static immersion tests of FeMnC in SBF with surface and solution analyses (SEM/EDX, XPS, ICP-OES) indicated that dissolution processes interfere with the formation of permeable surface coatings comprising hydroxides and salt