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230 results on '"Lohmann, V"'

7. Chemical interaction of B4C, B, and C with Mo/Si layered structures.

Author

de Rooij-Lohmann, V. I. T. A., Veldhuizen, L. W., Zoethout, E., Yakshin, A. E., van de Kruijs, R. W. E., Thijsse, B. J., Gorgoi, M., Schäfers, F., and Bijkerk, F.

Subjects
*OPTICS, *TOXICOLOGICAL interactions, *X-ray photoelectron spectroscopy, *CHEMICAL process control, *EXTREME ultraviolet lithography
Abstract

To enhance the thermal stability, B4C diffusion barrier layers are often added to Mo/Si multilayer structures for extreme ultraviolet optics. Knowledge about the chemical interaction between B4C and Mo or Si, however is largely lacking. Therefore, the chemical processes during annealing up to 600 °C of a Mo/B4C/Si layered structure have been investigated in situ with hard x-ray photoelectron spectroscopy and ex situ with depth profiling x-ray photoelectron spectroscopy. Mo/B/Si and Mo/C/Si structures have also been analyzed as reference systems. The chemical processes in these systems have been identified, with two stages being distinguished. In the first stage, B and C diffuse and react predominantly with Mo. MoSix forms in the second stage. If the diffusion barrier consists of C or B4C, a compound forms that is stable up to the maximum probed temperature and annealing time. We suggest that the diffusion barrier function of B4C interlayers as reported in literature can be caused by the stability of the formed compound, rather than by the stability of B4C itself. [ABSTRACT FROM AUTHOR]

Published
2010
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8. Enhanced diffusion upon amorphous-to-nanocrystalline phase transition in Mo/B4C/Si layered systems.

Author

De Rooij-Lohmann, V. I. T. A., Yakshin, A. E., Van De Kruijs, R. W. E., Zoethout, E., Kleyn, A. W., Keim, E. G., Gorgoi, M., Schäfers, F., Brongersma, H. H., and Bijkerk, F.

Subjects
*NANOCRYSTALS, *PHASE transitions, *MOLYBDENUM, *SILICON, *KIRKENDALL effect
Abstract

The effect of an amorphous-to-nanocrystalline phase transition on the diffusion across an interface layer of subnanometer thickness has been investigated in real-time. The diffusion in the Mo/B4C/Si thin film structure studied was found to instantaneously enhance by an order of magnitude upon the formation of nanocrystals inducing the atomic-scale onset of grain boundary diffusion. [ABSTRACT FROM AUTHOR]

Published
2010
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9. Membrane alterations induced by nonstructural proteins of human norovirus

Author

Doerflinger, SY, Cortese, M, Romero-Brey, I, Menne, Z, Tubiana, T, Schenk, C, White, PA, Bartenschlager, R, Bressanelli, S, Hansman, GS, Lohmann, V, Doerflinger, SY, Cortese, M, Romero-Brey, I, Menne, Z, Tubiana, T, Schenk, C, White, PA, Bartenschlager, R, Bressanelli, S, Hansman, GS, and Lohmann, V

Abstract

Human noroviruses (huNoV) are the most frequent cause of non-bacterial acute gastroenteritis worldwide, particularly genogroup II genotype 4 (GII.4) variants. The viral nonstructural (NS) proteins encoded by the ORF1 polyprotein induce vesical clusters harboring the viral replication sites. Little is known so far about the ultrastructure of these replication organelles or the contribution of individual NS proteins to their biogenesis. We compared the ultrastructural changes induced by expression of norovirus ORF1 polyproteins with those induced upon infection with murine norovirus (MNV). Characteristic membrane alterations induced by ORF1 expression resembled those found in MNV infected cells, consisting of vesicle accumulations likely built from the endoplasmic reticulum (ER) which included single membrane vesicles (SMVs), double membrane vesicles (DMVs) and multi membrane vesicles (MMVs). In-depth analysis using electron tomography suggested that MMVs originate through the enwrapping SMVs with tubular structures similar to mechanisms reported for picornaviruses. Expression of GII.4 NS1-2, NS3 and NS4 fused to GFP revealed distinct membrane alterations when analyzed by correlative light and electron microscopy. Expression of NS1-2 induced proliferation of smooth ER membranes forming long tubular structures that were affected by mutations in the active center of the putative NS1-2 hydrolase domain. NS3 was associated with ER membranes around lipid droplets (LDs) and induced the formation of convoluted membranes, which were even more pronounced in case of NS4. Interestingly, NS4 was the only GII.4 protein capable of inducing SMV and DMV formation when expressed individually. Our work provides the first ultrastructural analysis of norovirus GII.4 induced vesicle clusters and suggests that their morphology and biogenesis is most similar to picornaviruses. We further identified NS4 as a key factor in the formation of membrane alterations of huNoV and provide models of t

Published
2017

22. 45 RAPID AND EFFICIENT ANTIGEN PROCESSING AND PRESENTATION OF A PROTECTIVE AND IMMUNODOMINANT HLA-B*27-RESTRICTED HEPATITIS C VIRUS-SPECIFIC CD8+ T CELL EPITOPE

Author

Schmidt, J., primary, Iversen, A.K.N., additional, Tenzer, S., additional, Gostick, E., additional, Price, D.A., additional, Lohmann, V., additional, Bowness, P., additional, Schild, H., additional, Blum, H.E., additional, Klenerman, P., additional, Neumann-Haefelin, C., additional, and Thimme, R., additional

Published
2012
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48. Selective stimulation of hepatitis C virus and pestivirus NS5B RNA polymerase activity by GTP.

Author

Lohmann, V, Overton, H, and Bartenschlager, R

Abstract

NS5B of the hepatitis C virus is an RNA template-dependent RNA polymerase and therefore the key player of the viral replicase complex. Using a highly purified enzyme expressed with recombinant baculoviruses in insect cells, we demonstrate a stimulation of RNA synthesis up to 2 orders of magnitude by high concentrations of GTP but not with ATP, CTP, UTP, GDP, or GMP. Enhancement of RNA synthesis was found with various heteropolymeric RNA templates, with poly(C)-oligo(G)12 but not with poly(A)-oligo(U)12. Several amino acid substitutions in polymerase motifs B, C, and D previously shown to be crucial for RdRp activity were tested for GTP stimulation of RNA synthesis. Most of these mutations, in particular those affecting the GDD motif (motif C) strongly reduced or completely abolished activation by GTP, suggesting that the same NTP-binding site is used for stimulation and RNA synthesis. Since GTP did not affect the overall RNA binding properties or the elongation rate, high concentrations of GTP appear to accelerate a rate-limiting step at the level of initiation of RNA synthesis. Finally, enhancement of RNA synthesis by high GTP concentrations was also found with NS5B of the pestivirus classical swine fever virus, but not with the 3D polymerase of poliovirus. Thus, stimulation of RdRp activity by GTP is evolutionarily conserved between the closely related hepaciviruses and pestiviruses but not between these and the more distantly related picornaviruses.

Published
1999

50. Less impact of power failures due to substation automation

Author

Lohmann, V. and Preiss, Otto

Abstract

The management of power failures is a complex endeavour, which needs a diverse set of preventive and corrective measures in order to attain satisfying results. Substation Automations (SA) systems comprise, among others, an infrastructure of intelligent electronic devices (IED) for protection and control. This paper is an attempt to convey that SA can be used to effectively deal with the problems of power interruptions, in that its devices serve as data sources to assess the actual service conditions of main capital plant items, and in that they enable automated and intelligent power restoration procedures as a measure to reduce the power interruption duration, and to avoid the consequences of loss of power for the consumers business.

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