@article{Huber, author = {Huber, Albert}, title = {The gravitational field of a massless particle on the horizon of a stationary black hole}, series = {Classical and Quantum Gravity}, journal = {Classical and Quantum Gravity}, abstract = {In this work, the field of a gravitational shockwave generated by a massless point-like particle is calculated at the event horizon of a stationary Kerr-Newman black hole. Using the geometric framework of generalized Kerr-Schild deformations in combination with the spin-coefficient formalism of Newman and Penrose, it is shown that the field equations of the theory, at the event horizon of the black hole, can be reduced to a single linear ordinary differential equation for the so-called profile function of the geometry. This differential relation is solved exactly. Based on the results obtained, a physical interpretation is given for the found shockwave spacetime, and it is clarified how these results lead back to those of previous works on the subject, which deal with the much simpler cases of gravitational shockwaves in static black hole backgrounds.}, subject = {Gravitation}, language = {en} } @article{HoffmannKuba, author = {Hoffmann, Michael E. and Kuba, Markus}, title = {Logarithmic integrals, zeta values, and tiered binomial coeffcients}, series = {Monatshefte fuer Mathematik}, journal = {Monatshefte fuer Mathematik}, subject = {Integrals}, language = {en} } @article{BelkacemKupkaPhilidetetal., author = {Belkacem, K{\´e}vin and Kupka, Friedrich and Philidet, Jordan and Samadi, R{\´e}za}, title = {Surface effects and turbulent pressure. Assessing the Gas-Γ1 and Reduced-Γ1 empirical models.}, series = {Astronomy \& Astrophysics}, journal = {Astronomy \& Astrophysics}, subject = {Surface}, language = {en} } @article{PurtscherRothbauerKratzetal., author = {Purtscher, Michaela and Rothbauer, Mario and Kratz, Sebastian Rudi Adam and Bailey, Andrew and Lieberzeit, Peter and Ertl, Peter}, title = {A microfluidic impedance-based extended infectivity assay: combining retroviral amplification and cytopathic effect monitoring on a single lab-on-a-chip platform}, series = {Lab on a Chip}, volume = {2021}, journal = {Lab on a Chip}, number = {Issue 7}, pages = {1364 -- 1372}, abstract = {Detection, quantification and monitoring of virus - host cell interactions are of great importance when evaluating the safety of pharmaceutical products. With the wide usage of viral based vector systems in combination with mammalian cell lines for the production of biopharmaceuticals, the presence of replication competent viral particles needs to be avoided and potential hazards carefully assessed. Consequently, regulatory agencies recommend viral clearance studies using plaque assays or TCID50 assays to evaluate the efficiency of the production process in removing viruses. While plaque assays provide reliable information on the presence of viral contaminations, they are still tedious to perform and can take up to two weeks to finish. To overcome some of these limitations, we have automated, miniaturized and integrated the dual cell culture bioassay into a common lab-on-a-chip platform containing embedded electrical sensor arrays to enrich and detect infectious viruses. Results of our microfluidic single step assay show that a significant reduction in assay time down to 3 to 4 days can be achieved using simultaneous cell-based viral amplification, release and detection of cytopathic effects in a target cell line. We further demonstrate the enhancing effect of continuous fluid flow on infection of PG-4 reporter cells by newly formed and highly active virions by M. dunni cells, thus pointing to the importance of physical relevant viral-cell interactions.}, subject = {Tissue Engineering}, language = {en} } @article{ZupkovitzKabiljoKothmayeretal., author = {Zupkovitz, Gordin and Kabiljo, Julijan and Kothmayer, Michael and Schlick, Katharina and Sch{\"o}fer, Christian and Lagger, Sabine and Pusch, Oliver}, title = {Analysis of Methylation Dynamics Reveals a Tissue-Specific, Age-Dependent Decline in 5-Methylcytosine Within the Genome of the Vertebrate Aging Model Nothobranchius furzeri.}, series = {Frontiers in Molecular Biosciences}, volume = {8}, journal = {Frontiers in Molecular Biosciences}, number = {627143}, abstract = {Erosion of the epigenetic DNA methylation landscape is a widely recognized hallmark of aging. Emerging advances in high throughput sequencing techniques, in particular DNA methylation data analysis, have resulted in the establishment of precise human and murine age prediction tools. In vertebrates, methylation of cytosine at the C5 position of CpG dinucleotides is executed by DNA methyltransferases (DNMTs) whereas the process of enzymatic demethylation is highly dependent on the activity of the ten-eleven translocation methylcytosine dioxygenase (TET) family of enzymes. Here, we report the identification of the key players constituting the DNA methylation machinery in the short-lived teleost aging model Nothobranchius furzeri. We present a comprehensive spatio-temporal expression profile of the methylation-associated enzymes from embryogenesis into late adulthood, thereby covering the complete killifish life cycle. Data mining of the N. furzeri genome produced five dnmt gene family orthologues corresponding to the mammalian DNMTs (DNMT1, 2, 3A, and 3B). Comparable to other teleost species, N. furzeri harbors multiple genomic copies of the de novo DNA methylation subfamily. A related search for the DNMT1 recruitment factor UHRF1 and TET family members resulted in the identification of N. furzeri uhrf1, tet1, tet2, and tet3. Phylogenetic analysis revealed high cross-species similarity on the amino acid level of all individual dnmts, tets, and uhrf1, emphasizing a high degree of functional conservation. During early killifish development all analyzed dnmts and tets showed a similar expression profile characterized by a strong increase in transcript levels after fertilization, peaking either at embryonic day 6 or at the black eye stage of embryonic development. In adult N. furzeri, DNA methylation regulating enzymes showed a ubiquitous tissue distribution. Specifically, we observed an age-dependent downregulation of dnmts, and to some extent uhrf1, which correlated with a significant decrease in global DNA methylation levels in the aging killifish liver and muscle. The age-dependent DNA methylation profile and spatio-temporal expression characteristics of its enzymatic machinery reported here may serve as an essential platform for the identification of an epigenetic aging clock in the new vertebrate model system N. furzeri.}, subject = {Tissue Engineering}, language = {en} } @inproceedings{WiessnerMachacekLinkLeitner, author = {Wießner, Katharina and Machacek-Link, Thomas and Leitner, Rita}, title = {Encouraging the development of higher-order cognitive skills via applied exercises and web-based self-assessment to teach the basic principles in molecular biology.}, series = {PIXEL NPSE2021, M{\"a}rz 2021}, booktitle = {PIXEL NPSE2021, M{\"a}rz 2021}, abstract = {The responsibility of a lecturer is not only to share his or her knowledge with the students in an easy to understand manner, but also to help the students to embed new knowledge and to encourage the development of higher-order cognitive skills via applied exercises. In order to meet the growing demand for blended learning approaches a new course concept was established in autumn 2018. To enhance comprehension and to provide opportunities for self-assessment, web-based training units were implemented by using the interactive learning software "Articulate Storyline". Students had to prepare at home for the course units by completing interactive chapters. Their learning outcome was assessed by online quizzes at the end of each chapter. Online Training chapters allowed time to focus on selected topics and to repeat key messages in following presence units. Additionally, guided group exercises were performed to promote analytic skills and abstract thinking. The students had to apply and combine their knowledge to solve problem-based challenges. An optional revision course was offered to the students, which allowed for interactive repetition of the acquired knowledge with the focus on student-to-lecturer dialog. An analysis based on a written evaluation of this course resulted in a positive feedback from the students, in particular regarding the guided exercises and the offered revision course. According to the students the group exercises allowed to process the learned subjects, promoted the group climate and were a convenient diversion from the frontal lecture format. Students who attended the revision course on a regular basis showed a better performance at the final exam and exceeded especially at interdisciplinary questions. The first implementation of this master´s degree course indicated that the combination of web-based training elements with frontal lecture elements, guided exercises stimulating cognitive skills and an optional revision course can teach students the basics of biology in an understandable way. This course structure is especially applicable to teach basic subjects for groups of students with varying initial knowledge. Financial support from the City of Vienna project PBL in Molecular Life Science (21-06) is gratefully acknowledged.}, subject = {PBL}, language = {en} } @article{DeiningerWagnerHeimeletal., author = {Deininger, Christian and Wagner, Andrea and Heimel, Patrick and Salzer, Elias and Monforte Vila, Xavier and Weißenbacher, Nadja and Grillari, Johannes and Redl, Heinz and Wichlas, Florian and Freude, Thomas and Tempfer, Herbert and Teuschl-Woller, Andreas and Traweger, Andreas}, title = {Enhanced BMP-2-Mediated Bone Repair Using an Anisotropic Silk Fibroin Scaffold Coated with Bone-like Apatite}, series = {Int. J. Mol. Sci.}, volume = {23}, journal = {Int. J. Mol. Sci.}, number = {1 / 283}, abstract = {The repair of large bone defects remains challenging and often requires graft material due to limited availability of autologous bone. In clinical settings, collagen sponges loaded with excessive amounts of bone morphogenetic protein 2 (rhBMP-2) are occasionally used for the treatment of bone non-unions, increasing the risk of adverse events. Therefore, strategies to reduce rhBMP-2 dosage are desirable. Silk scaffolds show great promise due to their favorable biocompatibility and their utility for various biofabrication methods. For this study, we generated silk scaffolds with axially aligned pores, which were subsequently treated with 10× simulated body fluid (SBF) to generate an apatitic calcium phosphate coating. Using a rat femoral critical sized defect model (CSD) we evaluated if the resulting scaffold allows the reduction of BMP-2 dosage to promote efficient bone repair by providing appropriate guidance cues. Highly porous, anisotropic silk scaffolds were produced, demonstrating good cytocompatibility in vitro and treatment with 10× SBF resulted in efficient surface coating. In vivo, the coated silk scaffolds loaded with a low dose of rhBMP-2 demonstrated significantly improved bone regeneration when compared to the unmineralized scaffold. Overall, our findings show that this simple and cost-efficient technique yields scaffolds that enhance rhBMP-2 mediated bone healing.}, subject = {Tissue Engineering}, language = {en} } @article{HackethalDungelTeuschl, author = {Hackethal, Johannes and Dungel, Peter and Teuschl, Andreas Herbert}, title = {Frequently Used Strategies to Isolate Extracellular Matrix Proteins from Human Placenta and Adipose Tissue}, series = {Tissue Engineering Part C: Methods}, volume = {27}, journal = {Tissue Engineering Part C: Methods}, number = {12}, pages = {649 -- 660}, abstract = {The natural extracellular matrix (ECM) provides the optimal environment for cells. Many enzymatic or non-enzymatic based strategies to extract ECM proteins from tissues were published over the past years. However, every single isolation strategy reported so far is associated with specific bottlenecks. In this study, frequently used strategies to isolate ECM from human placenta or adipose tissue using Tris-, serum-, or pepsin-based buffers were compared. The resulting ECM proteins were biochemically characterized by analysis of cellular remnants using Hoechst DNA staining, glycosaminoglycan (GAG) content by dimethylmethylene blue, visualization of protein bands using sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis combined with amino acid quantification, and assessment of the proangiogenic profile using an angiogenesis array. Tris-NaCl-extracted ECM proteins showed a high heterogenic degree of extracted proteins, bioactive growth factors, and GAGs, but no collagen-I. Active serum-extracted ECM showed significant lower DNA remnants when compared with the Tris-NaCl isolation strategy. Pepsin-extracted ECM was rich in collagen-I and low amounts of remaining bioactive growth factors. This strategy was most effective to reduce DNA amounts when compared with the other isolation strategies. Pepsin-extracted ECM from both tissues easily gelled at 37°C, whereas the other extracted ECM strategies did not gel at 37°C (Tris-NaCl: liquid; serum: sponge). All relevant characteristics (DNA residues, ECM diversity and bioactivity, shape) of the extracted ECM proteins highly depend on its isolation strategy and could still be optimized. Impact statement The natural human extracellular matrix (ECM) is the ideal cell niche. Various strategies were reported to isolate human ECM components from various sources. In this article, we compared frequently used methods and compared their characteristics (DNA remnants, glycosaminoglycan content, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, amino acid quantification, angiogenesis array, and gel formation). We conclude that more research is still necessary to optimize current isolation approaches for in vitro or in vivo applications of human ECM.}, subject = {Tissue Engineering}, language = {en} } @article{KhimichProsolovMishurovaetal., author = {Khimich, Margarita A. and Prosolov, Konstantin A. and Mishurova, Tatiana and Evsevleev, Sergej and Monforte, Xavier and Teuschl, Andreas H. and Slezak, Paul and Ibragimov, Egor A. and Saprykin, Alexander A. and Kovalevskaya, Zhanna G. and Dmitriev, Andrey I. and Bruno, Giovanni and Sharkeev, Yurii P.}, title = {Advances in Laser Additive Manufacturing of Ti-Nb Alloys: From Nanostructured Powders to Bulk Objects}, series = {Nanomaterials (Basel)}, volume = {11}, journal = {Nanomaterials (Basel)}, number = {5 / 1159}, abstract = {The additive manufacturing of low elastic modulus alloys that have a certain level of porosity for biomedical needs is a growing area of research. Here, we show the results of manufacturing of porous and dense samples by a laser powder bed fusion (LPBF) of Ti-Nb alloy, using two distinctive fusion strategies. The nanostructured Ti-Nb alloy powders were produced by mechanical alloying and have a nanostructured state with nanosized grains up to 90 nm. The manufactured porous samples have pronounced open porosity and advanced roughness, contrary to dense samples with a relatively smooth surface profile. The structure of both types of samples after LPBF is formed by uniaxial grains having micro- and nanosized features. The inner structure of the porous samples is comprised of an open interconnected system of pores. The volume fraction of isolated porosity is 2 vol. \% and the total porosity is 20 vol. \%. Cell viability was assessed in vitro for 3 and 7 days using the MG63 cell line. With longer culture periods, cells showed an increased cell density over the entire surface of a porous Ti-Nb sample. Both types of samples are not cytotoxic and could be used for further in vivo studies.}, subject = {Tissue Engineering}, language = {en} } @article{FarokhiAleemardaniSolouketal., author = {Farokhi, Maryam and Aleemardani, Mina and Solouk, Atefeh and Mirzadeh, Hamid and Teuschl, Andreas Herbert and Redl, Heinz}, title = {Crosslinking strategies for silk fibroin hydrogels: promising biomedical materials}, series = {Biomedical Materials}, volume = {16}, journal = {Biomedical Materials}, number = {2}, pages = {022004}, abstract = {Due to their strong biomimetic potential, silk fibroin (SF) hydrogels are impressive candidates for tissue engineering, due to their tunable mechanical properties, biocompatibility, low immunotoxicity, controllable biodegradability, and a remarkable capacity for biomaterial modification and the realization of a specific molecular structure. The fundamental chemical and physical structure of SF allows its structure to be altered using various crosslinking strategies. The established crosslinking methods enable the formation of three-dimensional (3D) networks under physiological conditions. There are different chemical and physical crosslinking mechanisms available for the generation of SF hydrogels (SFHs). These methods, either chemical or physical, change the structure of SF and improve its mechanical stability, although each method has its advantages and disadvantages. While chemical crosslinking agents guarantee the mechanical strength of SFH through the generation of covalent bonds, they could cause some toxicity, and their usage is not compatible with a cell-friendly technology. On the other hand, physical crosslinking approaches have been implemented in the absence of chemical solvents by the induction of β-sheet conformation in the SF structure. Unfortunately, it is not easy to control the shape and properties of SFHs when using this method. The current review discusses the different crosslinking mechanisms of SFH in detail, in order to support the development of engineered SFHs for biomedical applications.}, subject = {Tissue Engineering}, language = {en} }