| 1. |
- Behle, Anna, et al.
(author)
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Manipulation of topoisomerase expression inhibits cell division but not growth and reveals a distinctive promoter structure in Synechocystis
- 2022
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In: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 50:22, s. 12790-12808
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Journal article (peer-reviewed)abstract
- In cyanobacteria DNA supercoiling varies over the diurnal cycle and is integrated with temporal programs of transcription and replication. We manipulated DNA supercoiling in Synechocystis sp. PCC 6803 by CRISPRi-based knockdown of gyrase subunits and overexpression of topoisomerase I (TopoI). Cell division was blocked but cell growth continued in all strains. The small endogenous plasmids were only transiently relaxed, then became strongly supercoiled in the TopoI overexpression strain. Transcript abundances showed a pronounced 5'/3' gradient along transcription units, incl. the rRNA genes, in the gyrase knockdown strains. These observations are consistent with the basic tenets of the homeostasis and twin-domain models of supercoiling in bacteria. TopoI induction initially led to downregulation of G+C-rich and upregulation of A+T-rich genes. The transcriptional response quickly bifurcated into six groups which overlap with diurnally co-expressed gene groups. Each group shows distinct deviations from a common core promoter structure, where helically phased A-tracts are in phase with the transcription start site. Together, our data show that major co-expression groups (regulons) in Synechocystis all respond differentially to DNA supercoiling, and suggest to re-evaluate the long-standing question of the role of A-tracts in bacterial promoters.
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| 2. |
- Frómeta, D., et al.
(author)
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Fracture Resistance of Advanced High-Strength Steel Sheets for Automotive Applications
- 2021
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In: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 52:2, s. 840-856
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Journal article (peer-reviewed)abstract
- The fracture resistance of different advanced high-strength steel (AHSS) sheets for automotive applications is investigated through conventional tensile tests, fracture toughness measurements, and hole expansion tests. Different fracture-related parameters, such as the true fracture strain (TFS), the true thickness strain (TTS), the fracture toughness at crack initiation (wie), the specific essential work of fracture (we), and the hole expansion ratio (HER), are assessed. The specific essential work of fracture (we) is shown to be a suitable parameter to evaluate the local formability and fracture resistance of AHSS. The results reveal that fracture toughness cannot be estimated from any of the parameters derived from tensile tests and show the importance of microstructural features on crack propagation resistance. Based on the relation fracture toughness-local formability, a new AHSS classification mapping accounting for global formability and cracking resistance is proposed. Furthermore, a physically motivated fracture criterion for edge-cracking prediction, based on thickness strain measurements in fatigue pre-cracked DENT specimens, is proposed.
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| 3. |
- Frómeta, D., et al.
(author)
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Microstructural effects on fracture toughness of ultra-high strength dual phase sheet steels
- 2021
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In: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 802
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Journal article (peer-reviewed)abstract
- The influence of microstructure on the fracture toughness of two industrially processed 1000 MPa dual-phase (DP) steel grades is investigated. Crack initiation and propagation resistance are evaluated by means of the essential work of fracture (EWF) methodology and the main damage and fracture mechanisms are investigated. The results are discussed in terms of the proportion and distribution of the different microstructural constituents, which is assessed by scanning electron microscopy (SEM), high-resolution electron backscatter diffraction (HR-EBSD) and nanoindentation hardness measurements. The investigations show that the strain-induced transformation of retained austenite to martensite (TRIP effect), may be detrimental to cracking resistance, even though it increases tensile properties. This phenomenon is attributed to a “brittle†network effect generated by the presence of hard fresh martensite islands in the fracture process zone. The connectivity of the hard secondary phases and the proportion of soft phase (ferrite) also have a major role in fracture toughness. The DP steel with the larger volume fraction of ferrite and homogeneously distributed martensite islands shows significantly higher crack propagation resistance. The contribution of necking to the ductile fracture process is evaluated by means of thickness measurements in fractured DENT specimens and the correlation between the specific essential work of fracture (we) and tensile properties is investigated. It is concluded that the global formability and cracking resistance of high strength DP steels can be balanced through microstructural tailoring. © 2020 The Author(s)
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| 4. |
- Rentrop, V, et al.
(author)
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Psychosocial emergency care in times of COVID-19: the Essen University Hospital concept for corona-infected patients, their relatives, and medical staff
- 2021
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In: International archives of occupational and environmental health. - : Springer Science and Business Media LLC. - 1432-1246 .- 0340-0131. ; 94:2, s. 347-350
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Journal article (other academic/artistic)abstract
- Due to the SARS CoV-2-virus (COVID-19), anxiety, distress, and insecurity occur more frequently. In particular, infected individuals, their relatives, and medical staff face an increased risk of high psychological distress as a result of the ongoing pandemic. Thus, structured psychosocial emergency concepts are needed. The University hospital of Essen has taken up this challenge by creating the PEC concept to reduce psychosocial long-term consequences for infected patients, relatives, and medical staff at the university hospital. The concept includes professional medical as well as psychological support to convey constructive coping strategies and the provision of adequate tools such as the low-threshold online training program (CoPE It), which is accessible via the webpage www.cope-corona.de.
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