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"Ernst, Wolfgang"
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Formation of bimetallic clusters in superfluid helium nanodroplets analysed by atomic resolution electron tomography
Structure, shape and composition are the basic parameters responsible for properties of nanoscale materials, distinguishing them from their bulk counterparts. To reveal these in three dimensions at the nanoscale, electron tomography is a powerful tool. Advancing electron tomography to atomic resolution in an aberration-corrected transmission electron microscope remains challenging and has been demonstrated only a few times using strong constraints or extensive filtering. Here we demonstrate atomic resolution electron tomography on silver/gold core/shell nanoclusters grown in superfluid helium nanodroplets. We reveal morphology and composition of a cluster identifying gold- and silver-rich regions in three dimensions and we estimate atomic positions without using any prior information and with minimal filtering. The ability to get full three-dimensional information down to the atomic scale allows understanding the growth and deposition process of the nanoclusters and demonstrates an approach that may be generally applicable to all types of nanoscale materials.
Advancing electron tomography to atomic resolution is a powerful and challenging process. Here, the authors demonstrate atomic resolution electron tomography on silver-gold core-shell nanoclusters grown in superfluid helium nanodroplets, revealing their three-dimensional morphology and composition.
Journal Article
Digital Memory and the Archive
In the popular imagination, archives are remote, largely obsolete institutions: either antiquated, inevitably dusty libraries or sinister repositories of personal secrets maintained by police states. Yet the archive is now a ubiquitous feature of digital life. Rather than being deleted, e-mails and other computer files are archived. Media software and cloud storage allow for the instantaneous cataloging and preservation of data, from music, photographs, and videos to personal information gathered by social media sites.
In this digital landscape, the archival-oriented media theories of Wolfgang Ernst are particularly relevant.Digital Memory and the Archive, the first English-language collection of the German media theorist's work, brings together essays that present Ernst's controversial materialist approach to media theory and history. His insights are central to the emerging field of media archaeology, which uncovers the role of specific technologies and mechanisms, rather than content, in shaping contemporary culture and society.
Ernst's interrelated ideas on the archive, machine time and microtemporality, and the new regimes of memory offer a new perspective on both current digital culture and the infrastructure of media historical knowledge. For Ernst, different forms of media systems-from library catalogs to sound recordings-have influenced the content and understanding of the archive and other institutions of memory. At the same time, digital archiving has become a contested site that is highly resistant to curation, thus complicating the creation and preservation of cultural memory and history.
eBook
Evaluation of an inducible knockout system in insect cells based on co-infection and CRISPR/Cas9
Due to comparably high product titers and low production costs, the baculovirus/insect cell expression system is considered a versatile production platform in the biopharmaceutical industry. Its excellence in producing complex multimeric protein assemblies, including virus-like particles (VLPs), which are considered promising vaccine candidates to counter emerging viral threats, made the system even more attractive. However, the co-formation of budded baculovirus during VLP production poses a severe challenge to downstream processing. In order to reduce the amount of budded baculovirus in the expression supernatant we developed an inducible knockout system based on CRISPR/Cas9 and co-infection with two baculoviral vectors: one bringing along the Cas9 nuclease and the other one having incorporated the sequence for sgRNA expression. With our set-up high titer viruses can be generated separately, as only when both viruses infect cells simultaneously a knockout can occur. When budding essential genes gp64 and vp80 were targeted for knockout, we measured a reduction in baculovirus titer by over 90%. However, as a consequence, we also determined lower overall eYFP fluorescence intensity showing reduced recombinant protein production, indicating that further improvements in engineering as well as purification are required in order to ultimately minimize costs and timeframes for vaccine production utilizing the baculovirus/insect cell expression system.
Journal Article
Ernst Ludwig Kirchner : imaginary travels
Throughout Ernst Ludwig Kirchner's career, one unifying theme emerges - the search for what he saw as unadulterated and primal. This volume explores the far-reaching influence of non-western art on Kirchner's oeuvre and the importance of his life in Davos, Switzerland, where he found a temporary peace despite the impending threat of censorship by the Nazis. Throughout the chapters of this book are reproductions of Kirchner's paintings as well as his sculptures, woodcuts, sketches, drawings, textiles, carvings, and furniture. Archival material in the form of letters and diary entries offer an unprecedented look into the artist's creative process. This study of one of the most talented and influential German Expressionist painters draws compelling conclusions about the influence of the imaginary on his work.
Book
Femtosecond photoexcitation dynamics inside a quantum solvent
The observation of chemical reactions on the time scale of the motion of electrons and nuclei has been made possible by lasers with ever shortened pulse lengths. Superfluid helium represents a special solvent that permits the synthesis of novel classes of molecules that have eluded dynamical studies so far. However, photoexcitation inside this quantum solvent triggers a pronounced response of the solvation shell, which is not well understood. Here, we present a mechanistic description of the solvent response to photoexcitation of indium (In) dopant atoms inside helium nanodroplets (He
N
), obtained from femtosecond pump–probe spectroscopy and time-dependent density functional theory simulations. For the In–He
N
system, part of the excited state electronic energy leads to expansion of the solvation shell within 600 fs, initiating a collective shell oscillation with a period of about 30 ps. These coupled electronic and nuclear dynamics will be superimposed on intrinsic photoinduced processes of molecular systems inside helium droplets.
Femtosecond laser spectroscopy has contributed to our understanding of structure and function of matter. Here, the authors explore the applicability of superfluid helium nanodroplets as a sample preparation method that allows investigation of previously inaccessible classes of tailor-made or fragile molecular systems.
Journal Article
Quantitative proteomic analysis of extracellular vesicles in response to baculovirus infection of a Trichoplusia ni cell line
Due to its outstanding suitability to produce complex biopharmaceutical products including virus-like particles and subunit vaccines, the baculovirus/insect cell expression system has developed into a highly popular production platform in the biotechnological industry. For high productivity, virus-cell communication and an efficient spreading of the viral infection are crucial, and, in this context, extracellular vesicles (EVs) might play a significant role. EVs are small particles, utilized by cells to transfer biologically active compounds such as proteins, lipids as well as nucleic acids to recipient cells for intracellular communication. Studies in mammalian cells showed that the release of EVs is altered in response to infection with many viruses, ultimately either limiting or fostering infection spreading. In this study we isolated and characterized EVs, from both uninfected and baculovirus infected Tnms42 insect cells. Via quantitative proteomic analysis we identified more than 3000 T . ni proteins in Tnms42 cell derived EVs, of which more than 400 were significantly differentially abundant upon baculovirus infection. Subsequent gene set enrichment analysis revealed a depletion of proteins related to the extracellular matrix in EVs from infected cultures. Our findings show a significant change of EV protein cargo upon baculovirus infection, suggesting a major role of EVs as stress markers. Our study might serve in designing new tools for process monitoring and control to further improve biopharmaceutical production within the baculovirus/insect cell expression system.
Journal Article
Experimental and theoretical investigations on the modulation capabilities of a sample of vertical cavity surface emitting laser diodes for atomic vapour applications
This paper discusses various frequency modulation and intensity modulation capabilities within a sample of direct laser current modulated identical vertical cavity surface emitting laser diodes. The presented analysis is based on measurements of the spectral amplitudes as a function of the applied modulation power at a constant modulation frequency of 3.517 GHz. Their evaluation by Bessel function fits produces the three modulation parameters: frequency modulation index, intensity modulation index (via the
α
parameter) and the side band asymmetry of the first order side bands. The variation of the laser diode’s modulation capability is discussed. It is found that the individual laser diodes show a significant variations in their modulation capabilities. Thus an experimental preselection of the laser diode is required to find laser diodes which are suitable as a light source for atomic vapour applications, with special emphasis on a coherent population trapping-based scalar magnetometers.
Journal Article