TY  - THES
A1  - Müller, Melanie
T1  - Untersuchung von Grenzflächenreaktionen von kristallisierenden Glasloten bei der Fügung von Hochtemperaturbrennstoffzellen
T1  - Investigation of interfacial reactions of crystallizing glass sealants at sealing of solid oxide fuel cells
N2  - Für die Fügung der Interkonnektoren einer Hochtemperaturbrennstoffzelle wurden in der hier vorliegenden Arbeit glaskeramische Lote entwickelt und untersucht. Es konnte ein hochviskoses Glas
gefunden werden, das trotz fehlendem Erweichen bei der Fügung eine stabile, gasdichte und elektrisch isolierende glaskeramische Fügung ausbildet. Auch während des Betriebs kommt es zu keinem Erweichen der Fügung. Weiter treten keine feststellbaren Reaktionen mit den potentiellen Reaktionspartnern, den Stahlelementen, auf. Es konnte eine Korrelation dieses Reaktionsverhaltens
mit dem Kristallisationsverhalten der Glaskeramik gefunden werden. Das Verhalten des Glaslotes
wurde über mehrere tausend Stunden unter Betriebsbedingungen beziehungsweise betriebsimulierenden Bedingungen untersucht. Dabei konnte die Kristallisationsentwicklung beschrieben werden.
Ein weiterer Aspekt der Arbeit war die Untersuchung des Einflusses der einzelnen Faktoren, denen
ein Glaslot während seines Einsatzes von der Fügung bis zum Betrieb ausgesetzt ist, wie die
Fügetemperatur, die Viskosität der eingesetzten glasbildenden Schmelze oder die Dualgasatmosphäre im Betrieb, auf das Gefüge und die Diffusion.
Hierbei konnte gezeigt werden, dass die Fügetemperatur mit Abstand den größten Einfluss auf die
Stabilität der Glaslotschicht hat. Diese bedingt nicht nur die Kinetik des Fließens und die Benetzung
des Stahls durch das Glas, sondern vor allem, welche Kristallphasen gebildet werden und
wie das finale Gefüge im Hinblick auf Kristallitgröße und –verteilung aussieht. So kommt es bei
höheren Temperaturen zu einem größeren Restglasphasenanteil und einem geringeren Kristallitanteil, was wiederum die Diffusion der Stahlelemente in die Glaslotschicht begünstigt.
N2  - This work describes the development and analysis of new glass ceramic sealants for the use in
solid oxide fuel cells. The sealant is applied to the sealing area of metallic interconnectors. The
developed sealant has a high viscosity in such a way as to keep its geometric form stable during
the sealing process and during the operation of a solid oxide fuel cell. This sealant enables a stable,
gastight and electrically insulating sealing. There are no reactions with the contacting materials,
the elements of the steel, even after extended time under operation or operation-like conditions.
This stability can be explained by the crystallization behaviour of the glass ceramic which forms
an interface layer. This behaviour was monitored over a few thousand hours.
Furthermore, the parameters, which have a potential influence on the glass ceramic during the
whole life cycle, the sealing and the operation, were examined. The parameters which were investigated
were in particular the sealing temperature, the viscosity of the glass, the operation time and
the dual gas atmosphere.
The sealing temperature has the most significant effect on the formation of the glass ceramic. It
defines the formation of the crystallites, the type as well as the size and allocation of the crystallites.
At a higher sealing temperature, for example, less crystallites and a larger glassy phase is
formed. This effect can lead to an increase of the diffusion processes.
Another relevant parameter is the viscosity of the glass, as a low viscosity increases the diffusion.
After extended operation time, a growth of the crystallites and a decrease of the amount of the
glassy phase was observed. This was indifferent to the other occuring factors like the applied voltage
or the dual gas atmosphere.
In conclusion, the newly developed glass ceramic sealant paves a way for the use of SOFC, in particular
for mobile applications, where the external mechanical stresses cause higher requirements
on the sealant.
KW  - Hochtemperaturbrennstoffzelle
KW  - Glaslot
KW  - SOFC
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-296871
ER  - 
TY  - JOUR
A1  - Ebert, Regina
A1  - Weissenberger, Manuel
A1  - Braun, Clemens
A1  - Wagenbrenner, Mike
A1  - Herrmann, Marietta
A1  - Müller‐Deubert, Sigrid
A1  - Krug, Melanie
A1  - Jakob, Franz
A1  - Rudert, Maximilian
T1  - Impaired regenerative capacity and senescence‐associated secretory phenotype in mesenchymal stromal cells from samples of patients with aseptic joint arthroplasty loosening
JF  - Journal of Orthopaedic Research
N2  - Aseptic loosening of total hip and knee joint replacements is the most common indication for revision surgery after primary hip and knee arthroplasty. Research suggests that exposure and uptake of wear by mesenchymal stromal cells (MSC) and macrophages results in the secretion of proinflammatory cytokines and local osteolysis, but also impaired cell viability and regenerative capacity of MSC. Therefore, this in vitro study compared the regenerative and differentiation capacity of MSC derived from patients undergoing primary total hip arthroplasty (MSCprim) to MSC derived from patients undergoing revision surgery after aseptic loosening of total hip and knee joint implants (MSCrev). Regenerative capacity was examined by measuring the cumulative population doubling (CPD) in addition to the number of passages until cells stopped proliferating. Osteogenesis and adipogenesis in monolayer cultures were assessed using histological stainings. Furthermore, RT‐PCR was performed to evaluate the relative expression of osteogenic and adipogenic marker genes as well as the expression of markers for a senescence‐associated secretory phenotype (SASP). MSCrev possessed a limited regenerative capacity in comparison to MSCprim. Interestingly, MSCrev also showed an impaired osteogenic and adipogenic differentiation capacity compared to MSCprim and displayed a SASP early after isolation. Whether this is the cause or the consequence of the aseptic loosening of total joint implants remains unclear. Future research should focus on the identification of specific cell markers on MSCprim, which may influence complication rates such as aseptic loosening of total joint arthroplasty to further individualize and optimize total joint arthroplasty.
KW  - aseptic loosening
KW  - mesenchymal stromal cells
KW  - regenerative capacity
KW  - senescence‐associated secretory phenotype
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238963
VL  - 40
IS  - 2
SP  - 513
EP  - 523
ER  - 
TY  - JOUR
A1  - Müller-Deubert, Sigrid
A1  - Seefried, Lothar
A1  - Krug, Melanie
A1  - Jakob, Franz
A1  - Ebert, Regina
T1  - Epidermal growth factor as a mechanosensitizer in human bone marrow stromal cells
JF  - Stem Cell Research
N2  - Epidermal growth factors (EGFs) e.g. EGF, heparin-binding EGF and transforming growth factor alpha and their receptors e.g. EGFR and ErbB2 control proinflammatory signaling and modulate proliferation in bone marrow stromal cells (BMSC). Interleukin-6 and interleukin-8 are EGF targets and participate in the inflammatory phase of bone regeneration via non-canonical wnt signaling. BMSC differentiation is also influenced by mechanical strain-related activation of ERK1/2 and AP-1, but the role of EGFR signaling in mechanotransduction is unclear. We investigated the effects of EGFR signaling in telomerase-immortalized BMSC, transfected with a luciferase reporter, comprising a mechanoresponsive AP1 element, using ligands, neutralizing antibodies and EGFR inhibitors on mechanotransduction and we found that EGF via EGFR increased the response to mechanical strain. Results were confirmed by qPCR analysis of mechanoresponsive genes. EGF-responsive interleukin-6 and interleukin-8 were synergistically enhanced by EGF stimulation and mechanical strain. We show here in immortalized and primary BMSC that EGFR signaling enhances mechanotransduction, indicating that the EGF system is a mechanosensitizer in BMSC. Alterations in mechanosensitivity and -adaptation are contributors to age-related diseases like osteoporosis and the identification of a suitable mechanosensitizer could be beneficial. The role of the synergism of these signaling cascades in physiology and disease remains to be unraveled.
KW  - mechanotransduction
KW  - bone marrow stromal cells
KW  - epidermal growth factor
KW  - signaling
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170247
VL  - 24
ER  - 
TY  - JOUR
A1  - Pilgram, Lisa
A1  - Eberwein, Lukas
A1  - Wille, Kai
A1  - Koehler, Felix C.
A1  - Stecher, Melanie
A1  - Rieg, Siegbert
A1  - Kielstein, Jan T.
A1  - Jakob, Carolin E. M.
A1  - Rüthrich, Maria
A1  - Burst, Volker
A1  - Prasser, Fabian
A1  - Borgmann, Stefan
A1  - Müller, Roman-Ulrich
A1  - Lanznaster, Julia
A1  - Isberner, Nora
A1  - Tometten, Lukas
A1  - Dolff, Sebastian
T1  - Clinical course and predictive risk factors for fatal outcome of SARS-CoV-2 infection in patients with chronic kidney disease
JF  - Infection
N2  - Purpose
The ongoing pandemic caused by the novel severe acute respiratory coronavirus 2 (SARS-CoV-2) has stressed health systems worldwide. Patients with chronic kidney disease (CKD) seem to be more prone to a severe course of coronavirus disease (COVID-19) due to comorbidities and an altered immune system. The study’s aim was to identify factors predicting mortality among SARS-CoV-2-infected patients with CKD.

Methods
We analyzed 2817 SARS-CoV-2-infected patients enrolled in the Lean European Open Survey on SARS-CoV-2-infected patients and identified 426 patients with pre-existing CKD. Group comparisons were performed via Chi-squared test. Using univariate and multivariable logistic regression, predictive factors for mortality were identified.

Results
Comparative analyses to patients without CKD revealed a higher mortality (140/426, 32.9% versus 354/2391, 14.8%). Higher age could be confirmed as a demographic predictor for mortality in CKD patients (> 85 years compared to 15–65 years, adjusted odds ratio (aOR) 6.49, 95% CI 1.27–33.20, p = 0.025). We further identified markedly elevated lactate dehydrogenase (> 2 × upper limit of normal, aOR 23.21, 95% CI 3.66–147.11, p < 0.001), thrombocytopenia (< 120,000/µl, aOR 11.66, 95% CI 2.49–54.70, p = 0.002), anemia (Hb < 10 g/dl, aOR 3.21, 95% CI 1.17–8.82, p = 0.024), and C-reactive protein (≥ 30 mg/l, aOR 3.44, 95% CI 1.13–10.45, p = 0.029) as predictors, while renal replacement therapy was not related to mortality (aOR 1.15, 95% CI 0.68–1.93, p = 0.611).

Conclusion
The identified predictors include routinely measured and universally available parameters. Their assessment might facilitate risk stratification in this highly vulnerable cohort as early as at initial medical evaluation for SARS-CoV-2.
KW  - chronic kidney disease
KW  - COVID-19
KW  - LEOSS
KW  - predictive factor
KW  - SARS-CoV-2
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-308957
SN  - 0300-8126
SN  - 1439-0973
VL  - 49
IS  - 4
ER  -