Ursache von Gleichtaktstörströmen in induktiven Ladesystemen (WPT-Systeme) und Vergleich zwischen gemessenen Störströmen mit der Feldstärkemessung

Induktive Ladesysteme oder WPT-Systeme (WPT= Wireless Power Transfer) für Elektrofahrzeuge, wie in Abbildung 1 dargestellt, werden seit einigen Jahren in unterschiedlichen Normungsgremien diskutiert. Die funktionale Beschreibung, z.B. Interoperabilität zwischen verschiedenen Systemen, strebt langsam einer Konsenslösung entgegen. Schließlich sollen die Normen der IEC 61980-Serie [2][3][5], der SAE J 2954 [8] und der ISO 19363 [6] noch im Jahr 2020 veröffentlicht bzw. aktualisiert werden. Die Anforderungen an die Störaussendung von WPT-Systemen werden jedoch noch intensiv in den Normungsgremien diskutiert. Aufgrund ihrer Eigenschaft, die Energie mittels eines hochfrequenten Signals zu übertragen, werden WPT-Systeme in der CISPR 11 als ISM-Geräte der Gruppe 2 eingeordnet. Entsprechend beschäftigt sich die Normenarbeitsgruppe CISPR/B mit einer Erweiterung der Norm um die Beschreibung der Messanforderungen für WPT-Systeme und der Vorgabe von Grenzwerten [4]. Induktive Ladesysteme übertragen die Energie mittels eines magnetischen Wechselfeldes zwischen zwei gekoppelten Resonanzkreisen, wie es Bild 1 zeigt. Für das Laden von PKWs mit einer Leistung zwischen 3. . . 22 kW wird eine Frequenz im Bereich zwischen 79. . . 90 kHz verwendet, auf welche die Resonanzkreise abgestimmt sind. Nahe am Resonanzpunkt kompensieren sich die imaginären Anteile der Impedanz und es wird im Wesentlichen Wirkleistung übertragen. Aufgrund der offenen Koppelstruktur existieren Streufelder, welche als Störaussendung bei der Feldstärkemessung zu bewerten sind

Histological Processing of CAD/CAM Titanium Scaffold after Long-Term Failure in Cranioplasty

Cranioplasty is a frequently performed procedure after craniectomy and includes several techniques with different materials. Due to high overall complication rates, alloplastic implants are removed in many cases. Lack of implant material osseointegration is often assumed as a reason for failure, but no study has proven this in cranioplasty. This study histologically evaluates the osteointegration of a computer-aided design and computer-aided manufacturing (CAD/CAM) titanium scaffold with an open mesh structure used for cranioplasty. A CAD/CAM titanium scaffold was removed due to late soft tissue complications 7.6 years after cranioplasty. The histological analyses involved the preparation of non-decalcified slices from the scaffold's inner and outer sides as well as a light-microscopic evaluation, including the quantification of the bone that had formed over the years. Within the scaffold pores, vital connective tissue with both blood vessels and nerves was found. Exclusive bone formation only occurred at the edges of the implant, covering 0.21% of the skin-facing outer surface area. The inner scaffold surface, facing towards the brain, did not show any mineralization at all. Although conventional alloplastic materials for cranioplasty reduce surgery time and provide good esthetic results while mechanically protecting the underlying structures, a lack of adequate stimuli could explain the limited bone formation found. CAD/CAM porous titanium scaffolds alone insufficiently osseointegrate in such large bone defects of the skull. Future research should investigate alternative routes that enable long-term osteointegration in order to reduce complication rates after cranioplasty. Opportunities could be found in mechano-biologically optimized scaffolds, material modifications, surface coatings, or other routes to sustain bone formation

On the field emission from Ni, Gd, and EuS evaporated on to Tungsten

Eckstein W, Georg KF, Heiland W, Kirschner J, Müller N. On the field emission from Ni, Gd, and EuS evaporated on to Tungsten. Zeitschrift für Naturforschung, A: Journal of Physical Sciences. 1970;25(?):1981-1982

Biomechanical Assessment of the Validity of Sheep as a Preclinical Model for Testing Mandibular Fracture Fixation Devices

Mandibular fracture fixation and reconstruction are usually performed using titanium plates and screws, however, there is a need to improve current fixation techniques. Animal models represent an important step for the testing of new designs and materials. However, the validity of those preclinical models in terms of implant biomechanics remains largely unknown. In this study, we investigate the biomechanics of the sheep mandible as a preclinical model for testing the mechanical strength of fixation devices and the biomechanical environment induced on mandibular fractures. We aimed to assess the comparability of the biomechanical conditions in the sheep mandible as a preclinical model for human applications of fracture fixation devices and empower analyses of the effect of such defined mechanical conditions on bone healing outcome. We developed 3D finite element models of the human and sheep mandibles simulating physiological muscular loads and three different clenching tasks (intercuspal, incisal, and unilateral). Furthermore, we simulated fractures in the human mandibular body, sheep mandibular body, and sheep mandibular diastema fixated with clinically used titanium miniplates and screws. We compared, at the power stroke of mastication, the biomechanical environment (1) in the healthy mandibular body and (2) at the fracture sites, and (3) the mechanical solicitation of the implants as well as the mechanical conditions for bone healing in such cases. In the healthy mandibles, the sheep mandibular body showed lower mechanical strains compared to the human mandibular body. In the fractured mandibles, strains within a fracture gap in sheep were generally not comparable to humans, while similar or lower mechanical solicitation of the fixation devices was found between the human mandibular body fracture and the sheep mandibular diastema fracture scenarios. We, therefore, conclude that the mechanical environments of mandibular fractures in humans and sheep differ and our analyses suggest that the sheep mandibular bone should be carefully re-considered as a model system to study the effect of fixation devices on the healing outcome. In our analyses, the sheep mandibular diastema showed similar mechanical conditions for fracture fixation devices to those in humans

Deletion of the receptor tyrosine kinase Tyro3 inhibits synovial hyperplasia and bone damage in arthritis

Objective: To test whether the tyrosine kinase Tyro3 affects arthritis. Tyro3, the ligand of growth arrest–specific protein 6 (GAS6) is a receptor tyrosine kinase involved in cell survival. Tyro3 and GAS6 are expressed in the arthritic synovium, and in vitro studies have shown their role in osteoclast differentiation. Methods: Bone was assessed by micro CT and histomorphometry in Tyro3-deficient (Tyro3−/−) and wild-type mice. Arthritis was induced in both genotypes, and Gas6 level was measured by ELISA. Synovitis, synovial hyperplasia, bone erosion, osteoclast activation and osteoclast gene expression were assessed by histomorphometry and reverse transcriptase–PCR, respectively. In vitro osteoclast differentiation assays were performed in Tyro3−/− and wild-type mice. Furthermore, effects of Tyro3 and GAS6 on human synovial fibroblast proliferation and osteoclastogenesis were assessed in human cells. Results: Tyro3−/− mice had significantly higher bone mass than wild-type littermates. Induction of arthritis increased GAS6 serum levels. Arthritic Tyro3−/− mice showed less synovial hyperplasia, osteoclast numbers and bone damage compared with controls. In vivo expression of osteoclast-associated receptor and receptor activator of nuclear factor-κB and in vitro osteoclastogenesis were impaired in Tyro3−/− mice. GAS6 also induced synovial fibroblast proliferation and osteoclast differentiation in human cells in Tyro3-dependent manner. Conclusions: These findings indicate that Tyro3 is a critical signal for synovial hyperplasia, osteoclast differentiation and bone erosion during arthritis. GAS6 and Tyro3 therefore constitute therapeutic targets to inhibit synovial hyperplasia and associated bone erosion

High level of functional dickkopf-1 predicts protection from syndesmophyte formation in patients with ankylosing spondylitis

Introduction: The molecular mechanisms of syndesmophyte formation in ankylosing spondylitis (AS) are yet to be characterised. Molecules involved in bone formation such as Wnt proteins and their antagonists probably drive syndesmophyte formation in AS. Methods: This study investigated sequential serum levels of functional dickkopf-1 (Dkk1), a potent Wnt antagonist involved in bone formation in arthritis, by capture ELISA with its receptor LRP6 in 65 AS patients from the German Spondyloarthritis Inception Cohort. Dkk1 levels were then related to structural progression (syndesmophyte formation) as well as sclerostin and C-reactive protein (CRP) levels. Results: Functional Dkk1 levels were significantly (p=0.025) higher in patients with no syndesmophyte growth (6.78±5.48 pg/ml) compared with those with syndesmophyte growth (4.13±2.10 pg/ml). Dkk1 levels were highly correlated to serum sclerostin levels (r=0.71, 95% CI 0.53 to 0.82; p<0.001) but not to CRP (r=0.15, 95% CI −0.10 to 0.38; p=0.23). Conclusion: AS patients with no syndesmophyte formation show significantly higher functional Dkk1 levels suggesting that blunted Wnt signalling suppresses new bone formation and consequently syndesmophyte growth and spinal ankylosis. Similar to serum sclerostin levels, the functional Dkk1 level thus emerges as a potential biomarker for structural progression in patients with AS

Improved in vivo osseointegration and degradation behavior of PEO surface-modified WE43 magnesium plates and screws after 6 and 12 months

Magnesium is a highly promising candidate with respect to its future use as a material for resorbable implants. When magnesium degrades, hydrogen gas is released. High doses of gas emergence are reported to impair osseointegration and may therefore lead to fixation failure. The successful delay and reduction of the degradation rate by applying plasma electrolytic oxidation (PEO) as a post processing surface modification method for magnesium alloy has recently been demonstrated. The aim of this study was thus to compare the degradation behavior of a WE43-based plate system with and without respective PEO surface modification and to further investigate osseointegration, as well as the resulting effects on the surrounding bony tissue of both variants in a miniature pig model. WE43 magnesium screws and plates without (WE43) and with PEO surface modification (WE43-PEO) were implanted in long bones of Go spacing diaeresis ttingen Miniature Pigs. At six and twelve months after surgery, micro-CT and histomorphometric analysis was performed. Residual screw volume (SV/TV; WE43: 28.8 +/- 21.1%; WE43-PEO: 62.9 +/- 31.0%; p = 0.027) and bone implant contact area (BIC; WE43: 18.1 +/- 21.7%; WE43-PEO: 51.6 +/- 27.7%; p = 0.015) were increased after six months among the PEO-modified implants. Also, surrounding bone density within the cortical bone was not affected by surface modification (BVTV; WE43: 76.7 +/- 13.1%; WE43-PEO: 73.1 +/- 16.2%; p = 0.732). Intramedullar (BV/TV; WE43: 33.2 +/- 16.7%; WE43-PEO 18.4 +/- 9.0%; p = 0.047) and subperiosteal (bone area; WE43: 2.6 +/- 3.4 mm2; WE43-PEO: 6,9 +/- 5.2 mm2; p = 0.049) new bone formation was found for both, surface-modified and nonsurface-modified groups. After twelve months, no significant differences of SV/TV and BV/TV were found between the two groups. PEO surface modification of WE43 plate systems improved osseointegration and significantly reduced the degradation rate within the first six months in vivo. Osteoconductive and osteogenic stimulation by WE43 magnesium implants led to overall increased bone growth, when prior PEO surface modification was conducted