Spinal stabilization for patients with metastatic lesions of the spine using a titanium spacer

Anterior decompression in spinal metastases of the corporal type with impending (n=5) or present (n=36) neurological complications was performed in 41 patients. For reconstruction, a titanium cylinder was inserted after spondylectomy and augmented with an anterior plate. The titanium implant can easily be adjusted to the length needed without necessitating expensive additional equipment. Outside the patient the implant is filled with polymethylmetacrylate, facilitating plate transfixation for rotational locking. There was a 30-day mortality of 9.7%. Pain relief was apparent in 38 of 41 patients (92.7%), and motor improvement was manifest in 31 of 35 cases (88.6%). Six patients did not present with any neurological symptoms pre- or postoperatively. Neurological deterioration was registered in only 1 case (2.4%). Surgical efficacy was maintained until the death of the patients. Though tumor recurrence at a different spinal level led to consecutive surgery in 5 patients, no implant dislocation occurred during the observation period (maximum 44 months), characterizing the procedure as a mechanically reliable and safe technique

Agentenbasierende Finanzmarktmodelle

In this thesis we look at different models of financial markets whose dynamic is based on the herding behaviour of the agents trading on the market. Kirman introduced the first model of this kind in the year 1991. We also consider another model that is introduced by Alfarano et al. in the year 2007. The basic assumptions of these models are that there is a fixed number of agents N, who trade on the market. These agents can be divided into two groups. We call them optimists and pessimists. The dynamic of these models is based on the fact that the agents switch between the two groups. Important for the state of the system is not the membership of each agent in one of the groups but the relation between optimistic and pessimistic agents. Due to the fact that the number of agents is constant, it is sufficient to look at the number of optimistic agents. In the two models mentioned above, the number of optimistic agents is modelled as a birth and death process. At first, we look at the behaviour of these birth and death processes in the case that the number of agents N tends to infinity. After that, we extend the model with another agent, representing further influences for the behaviour of the optimists and pessimists whom we call “super agent” and look at different limiting cases for this new model.In dieser Arbeit betrachten wir verschiedene Finanzmarktmodelle, deren Dynamik auf dem Kommunikationsverhalten der am Markt handelnden Agenten basiert. Das erste Modell dieser Art hat der Ökonom Kirman im Jahr 1991 beschrieben. Ein weiteres Modell, das wir betrachten, stammt aus einem Artikel von Alfarano et al. Aus dem Jahr 2007. Die Modelle basieren im Wesentlichen auf den folgenden Annahmen: Es gibt eine feste Anzahl Agenten N, die am Markt handeln. Diese Agenten lassen sich in zwei Gruppen aufteilen. Diese Gruppen werden wir als Optimisten und Pessimisten bezeichnen. Die Dynamik des Modells entsteht daraus, dass die Agenten zwischen diesen beiden Gruppen hin und her wechseln. In den beiden oben genannten Modellen wird die Dynamik des Modells durch einen Geburts- und Todesprozess modelliert. Zunächst betrachten wir das Verhalten dieser Geburts- und Todesprozesse für den Fall betrachten, dass die Anzahl der Agenten N gegen unendlich strebt. Danach erweitern wir das Modell und betrachten verschiedene Grenzverhalten im erweiterten Modell

A statistical equilibrium model of competitive firms

We find that the empirical density of firm profit rates, measured as returns on assets, is markedly non-Gaussian and reasonably well described by an exponential power (or Subbotin) distribution. We start from a statistical equilibrium model that leads to a stationary Subbotin density in the presence of complex interactions among competitive heterogeneous firms. To investigate the dynamics of firm profitability, we construct a diffusion process that has the Subbotin distribution as its stationary probability density. This leads to a phenomenologically inspired interpretation of variations in the shape parameter of the Subbotin distribution, which essentially measures the competitive pressure in and across industries. Our findings have profound implications both for the previous literature on the ‘persistence of profits’ as well as for understanding competition as a dynamic process. Our main formal finding is that firms' idiosyncratic efforts and the tendency for competition to equalize profit rates are two sides of the same coin, and that a ratio of these two effects ultimately determines the dispersion of the equilibrium distribution

„Die Jüdische Allgemeine“. Persönliches Porträt einer Instanz unter den jüdischen Publikationen in Deutschland

Ralph Giordano ist Schriftsteller, Publizist, Aufklärer, eine morali- sche Instanz – und der dienstälteste Mitarbeiter der „Jüdischen All- gemeinen“. Auch heute noch, mit seinen 90 Jahren, meldet er sich in der Wochenzeitung für Politik, Kultur, Religion und Jüdisches Le- ben zu Wort, ruft regelmäßig in der Redaktion an, weist auf wichtige Themen hin, verfasst Texte. Erst kürzlich hat die Zeitung seine Rede dokumentiert, die er anlässlich der Vorstellung eines Forschungspro- jektes über NS-Kontinuitäten im Bonner Justizministerium in Berlin hielt. Giordano und seine Geschichte repräsentieren einen wichtigen Teil des Selbstverständnisses der Zeitung. Er schafft es, wie sein Schriftstellerkollege Günter Kunert unlängst feststellte, die Leser „in die Lage der Verfolgten mit einzubeziehen und ihnen damit eine Ahnung und ein Mitempfinden zu ermöglichen“. Giordano ist Überle- bender der Shoa – er repräsentiert in diesem Sinne ein Fundament, auf dem diese Zeitung steht. (...

Operative Behnadlungsstrategien bei Femurmetastasen

Weder Deckblatt noch Ihaltsverzeischnis vorhanden

The in vitro viability and growth of fibroblasts cultured in the presence of different bone grafting materials (NanoBone® and Straumann Bone Ceramic®)

Different clinical applications, including dentistry, are making increasing demands on bone grafting material. In the present study we have analysed the viability, proliferation and growth characteristics of fibroblasts cultured in vitro together with two different bone grafting materials, NanoBone® and Straumann Bone Ceramic®, over a period of 24 and 28 days respectively. Viability was measured at least every 72 hours by using the alamarBlue assay, a test that measures quantitatively cell proliferation and viability but does not require cell fixation or extraction. After one week of culture fibroblast viability was as high as in controls for both grafting materials and remained high (> 90%) for the duration of the experiment. Cell growth was evaluated microscopically. Scanning electron microscopy revealed a dense fibroblast growth at the surface of both bone grafting materials after three weeks of in vitro culture. Generally, our in vitro analyses contribute to further insights into cell - scaffold interactions

High concentrations of polyelectrolyte complex nanoparticles decrease activity of osteoclasts

Fracture treatment in osteoporotic patients is still challenging. Osteoporosis emerges when there is an imbalance between bone formation and resorption in favor of resorption by osteoclasts. Thus, new implantmaterials for osteoporotic fracture treatment should promote bone formation and reduce bone resorption. Nanoparticles can serve as drug delivery systems for growth factors like Brain-Derived Neurotrophic Factor (BDNF), which stimulated osteoblast differentiation. Therefore, polyelectrolyte complex nanoparticles (PEC-NPs) consisting of poly(l-lysine) (PLL) and cellulose sulfate (CS), with or without addition of BDNF, were used to analyze their effect on osteoclasts in vitro. Live cell images showed that osteoclast numbers decreased after application of high PLL/CS PEC-NPs concentrations independent of whether BDNF was added or not. Real-time RT-PCR revealed that relative mRNA expression of cathepsin K and calcitonin receptor significantly declined after incubation of osteoclasts with high concentrations of PLL/CS PEC-NPs. Furthermore, Enzyme-Linked Immunosorbent Assay indicated that tartrate-resistant acidic phosphatase 5b activity was significantly reduced in the presence of high PLL/CS PEC-NPs concentrations. Consistent with these results, the pit formation analysis showed that less hydroxyapatite was resorbed by osteoclasts after incubation with high concentrations of PLL/CS PEC-NPs. BDNF had no influence on osteoclasts. We conclude that highly concentrated PLL/CS PEC-NPs dosages decreased osteoclastogenesis and osteoclasts activity. Moreover, BDNF might be a promising growth factor for osteoporotic fracture treatment since it did not increase osteoclast activity. © 2019 by the authors

The biodegradation of hydroxyapatite bone graft substitutes in vivo

Hydroxyapatite (HA) ceramics are widely used for bone reconstruction. They are osteoconductive and serve as structural scaffolds for the deposition of new bone. Generally, scaffold materials should be degradable as they affect the mechanical properties of the reconstructed bone negatively. Degradation by osteoclasts during the bone remodelling process is desirable but often does not take place. In the current study we analysed by light microscopy the degradation of two granular HA implants in critically sized defects in the mandibula of Goettingen mini-pigs five weeks after implantation. Bio-Oss® consists of sintered bovine bone and NanoBone® is a synthetic HA produced in a sol-gel process in the presence of SiO2. We found that both biomaterials were degraded by osteoclasts with ruffled borders and acid phosphatase activity. The osteoclasts created resorption lacunae and resorptive trails and contained mineral particles. Frequently, resorption surfaces were in direct contact with bone formative surfaces on one granule. Granules, especially of NanoBone®, were also covered by osteoclasts if located in vascularised connective tissue distant from bone tissue. However, this usually occurred without the creation of resorption lacunae. The former defect margins consisted of newly formed bone often without remnants of bone substitutes. Our results show that the degradation of both biomaterials corresponds to the natural bone degradation processes and suggest the possibility of complete resorption during bone remodelling