Entwicklung eines Verfahrens zum transvaskulären Aortenklappenersatz

Bei einem stetig zunehmenden Patientengut mit behandlungsbedürftigen Aortenklappenvitien und relevanten Begleiterkrankungen, welche das Risiko eines operativen Klappenersatzes erhöhen, wurde ein Verfahren zum transvaskulären Ersatz der Aortenklappe entwickelt. In umfangreichen In-vitro-Experimenten konnte gezeigt werden, dass eine biologische Herzklappenprothese, die in das proximale Ende eines selbstexpandierenden Nitinolstents eingenäht wurde, nach Zusammenfalten und Implantation mit einem 7 mm dicken Katheter strömungsdynamisch einer nativen Herklappe ähnliche Eigenschaften in einem künstlichen Kreislaufmodell aufweist. Der Aortenklappenstent wurde über einen Zugang von der Arteria subclavia unter Röntgendurchleuchtung erfolgreich in Schweine am schlagenden Herzen implantiert, indem beim Freisetzen des Klappenstents aus dem Katheter die alte Aortenklappe gegen die Wand gepresst wurde, während sich gleichzeitig die Bioprothese orthotop entfaltete. Unter Steigerung des Blutdruckes und der Pulsfrequenz durch Katecholamininfusionen konnte sowohl im Katheterrückzug als auch bei den Dopplerflussmessungen mittels transösophagealer Echokardiographie keine Fehlfunktion des Aortenklappenstents festgestellt werden. Dieses neu entwickelte Verfahren des transvaskulären Klappenersatzes, welche minimalinvasiv ohne Narkose und ohne Eröffnung des Brustkorbes möglich ist, kann zukünftig bei Hochrisikopatienten eine alternative Behandlungsmethode für Aortenklappenerkrankungen darstellen

Angiotensin-converting enzyme insertion/deletion polymorphism does not influence the restenosis rate after coronary stent implantation

Background. Experimental studies have shown an activation of the angiotensin-converting enzyme (ACE) system as a response to endothelial injury. Recent publications have elucidated the hypothesis that the ACE gene polymorphism may influence the level of late luminal loss after coronary stent implantation. It is still unclear whether the polymorphism of the angiotensin gene is a major predictor of the extent of neointimal hyperplasia. In this multicenter study, we therefore tested the relationship between the ACE gene polymorphism and the restenosis rate after coronary stent implantation. Methods: As a substudy of the optimization with intracoronary, ultrasound (ICUS) to reduce stent restenosis (OPTICUS) study, we analyzed ACE serum levels and the ACE gene polymorphism in 154 patients at 9 different centers. All patients underwent elective coronary stent implantation in a stenosis of a major coronary vessel. Balloon inflations were repeated until a satisfactory result was achieved in on-line quantitative coronary angiography or ICUS fulfilling the OPTICUS study criteria. After follow-up of 6 months, all patients underwent reangiography tinder identical projections as the baseline procedure. A blinded quantitative analysis of the initial procedure as well as the follow-up examinations were performed by an independent core laboratory. ACE gene polymorphism and ACE serum activity were measured at the 6-month follow-up in a double-blinded setting. Results: With respect to the ACE gene polymorphism, there were three subgroups: DID genotype (48 patients), ID (83 patients) and 11 (23 patients). The subgroups did not differ in regard to age, gender, extent of coronary artery disease, stenosis length, initial degree of stenosis or degree of stenosis after stent implantation. In all, 39 patients (25.3%) had significant restenosis: 12 DD patients (25.0%), 18 ID patients (21.7%) and 9 II patients (39.1%) (odds ratio 2.164, 95% confidence interval 0.853-5.493). We obtained the following results for ACE serum levels: 0.53 mumol/l/s in the DD subgroup, 0.29 mumol/l/s in the ID

Towards Evaluating User Profiling Methods Based on Explicit Ratings on Item Features

In order to improve the accuracy of recommendations, many recommender systems nowadays use side information beyond the user rating matrix, such as item content. These systems build user profiles as estimates of users' interest on content (e.g., movie genre, director or cast) and then evaluate the performance of the recommender system as a whole e.g., by their ability to recommend relevant and novel items to the target user. The user profile modelling stage, which is a key stage in content-driven RS is barely properly evaluated due to the lack of publicly available datasets that contain user preferences on content features of items. To raise awareness of this fact, we investigate differences between explicit user preferences and implicit user profiles. We create a dataset of explicit preferences towards content features of movies, which we release publicly. We then compare the collected explicit user feature preferences and implicit user profiles built via state-of-the-art user profiling models. Our results show a maximum average pairwise cosine similarity of 58.07\% between the explicit feature preferences and the implicit user profiles modelled by the best investigated profiling method and considering movies' genres only. For actors and directors, this maximum similarity is only 9.13\% and 17.24\%, respectively. This low similarity between explicit and implicit preference models encourages a more in-depth study to investigate and improve this important user profile modelling step, which will eventually translate into better recommendations

Effect of Tris, MOPS, and phosphate buffers on the hydrolysis of polyethylene terephthalate films by polyester hydrolases

The enzymatic degradation of polyethylene terephthalate (PET) occurs at mild reaction conditions and may find applications in environmentally friendly plastic waste recycling processes. The hydrolytic activity of the homologous polyester hydrolases LC cutinase (LCC) from a compost metagenome and TfCut2 from Thermobifida fusca KW3 against PET films was strongly influenced by the reaction medium buffers tris(hydroxymethyl)aminomethane (Tris), 3-(N-morpholino)propanesulfonic acid (MOPS), and sodium phosphate. LCC showed the highest initial hydrolysis rate of PET films in 0.2 M Tris, while the rate of TfCut2 was 2.1-fold lower at this buffer concentration. At a Tris concentration of 1 M, the hydrolysis rate of LCC decreased by more than 90% and of TfCut2 by about 80%. In 0.2 M MOPS or sodium phosphate buffer, no significant differences in the maximum initial hydrolysis rates of PET films by both enzymes were detected. When the concentration of MOPS was increased to 1 M, the hydrolysis rate of LCC decreased by about 90%. The activity of TfCut2 remained low compared to the increasing hydrolysis rates observed at higher concentrations of sodium phosphate buffer. In contrast, the activity of LCC did not change at different concentrations of this buffer. An inhibition study suggested a competitive inhibition of TfCut2 and LCC by Tris and MOPS. Molecular docking showed that Tris and MOPS interfered with the binding of the polymeric substrate in a groove located at the protein surface. A comparison of the Ki values and the average binding energies indicated MOPS as the stronger inhibitor of the both enzymes

Submodular Mean Field Games. Existence and Approximation of Solutions

Dianetti J, Ferrari G, Fischer M, Nendel M. Submodular Mean Field Games. Existence and Approximation of Solutions. Center for Mathematical Economics Working Papers. Vol 621. Bielefeld: Center for Mathematical Economics; 2019.We study mean field games with scalar Itô-type dynamics and costs that are submodular with respect to a suitable order relation on the state and measure space. The submodularity assumption has a number of interesting consequences. Firstly, it allows us to prove existence of solutions via an application of Tarski's fixed point theorem, covering cases with discontinuous dependence on the measure variable. Secondly, it ensures that the set of solutions enjoys a lattice structure: in particular, there exist a minimal and a maximal solution. Thirdly, it guarantees that those two solutions can be obtained through a simple learning procedure based on the iterations of the best-response-map. The mean field game is first defined over ordinary stochastic controls, then extended to relaxed controls. Our approach allows also to treat a class of submodular mean field games with common noise in which the representative player at equilibrium interacts with the (conditional) mean of its state's distribution