26 research outputs found
Persistent hepatitis C virus infection in vitro: coevolution of virus and host.
The virological and cellular consequences of persistent hepatitis C virus (HCV) infection have been elusive due to the absence of the requisite experimental systems. Here, we report the establishment and the characteristics of persistent in vitro infection of human hepatoma-derived cells by a recently described HCV genotype 2a infectious molecular clone. Persistent in vitro infection was characterized by the selection of viral variants that displayed accelerated expansion kinetics, higher peak titers, and increased buoyant densities. Sequencing analysis revealed the selection of a single adaptive mutation in the HCV E2 envelope protein that was largely responsible for the variant phenotype. In parallel, as the virus became more aggressive, cells that were resistant to infection emerged, displaying escape mechanisms operative at the level of viral entry, HCV RNA replication, or both. Collectively, these results reveal the existence of coevolutionary events during persistent HCV infection that favor survival of both virus and host
Assessing the impact of correlated geotechnical properties on the behaviour of retaining structures
This study investigates the geotechnical intricacies of Copenhagen's Quaternary upper clay till deposits, characterized as highly over-consolidated and significantly heterogeneous, and their impact on the structural performance of secant pile walls. Through rigorous analysis, 5000 samples were generated using multivariate distribution functions. These functions were developed to probabilistically calibrate the HS-small constitutive model, taking cross correlations into account. Additionally, 5000 more samples were generated assuming independence. These samples serve as the basis for a finite element model, providing crucial data on lateral wall deflections and bending moments. The impact of cross correlations among geotechnical properties on secant pile wall response is evident. The study quantifies this impact, showing a substantial reduction in standard deviation for lateral deflections (about 20%) compared to interdependent samples. The maximum bending moment during the final excavation stage sees a more modest 50% decrease. This study not only sheds light on the importance of considering dependencies among geotechnical properties in deep excavation design but also provides a practical framework for optimizing performance and safety in similar projects
Fault rupture and kinematic distress of earth filled embankments
Summarization: According to common practice the seismic design of any type of structure or infrastructure is focused on the
inertial loading and the resulting distress generated due to the imposed ground shaking. Regarding the effects of
fault rupture on seismic design, seismic norms contain mainly provisions that are related to the citation of the
structures/geostructures. Moreover, the additional distress imposed to large-scale structures (like bridges,
lifelines, dams, or earth-filled embankments) by the applied permanent deformations produced during a
potential fault rupture may not be possible to be avoided. As in many cases the exact location of faults is not
known, especially when surface scarps are not present, the consequences of the permanent deformations in
large-scale structures should be carefully and realistically evaluated. The current study examines numerically
the behavior of earth-filled embankments, focusing on their kinematic distress due to fault rupture propagation.
Apart from a brief literature review of the problem, a parametric study is conducted in order to investigate the
role of the main parameters involved. The results indicate that the effects of fault rupturing in earth-filled
embankments should be treated with caution. Additionally, the resulting kinematic distress should not be
disregarded in the stability assessment, and therefore, it should be taken into account in the overall seismic
design of the embankmentsΠαρουσιάστηκε στο: The 14 th World Conference on Earthquake Engineerin
Scanning Electron Microscopy and clay geomaterials:From sample preparation to fabric orientation quantification
Failure mechanisms of landfills under dynamic loading
Seismic stability of above-ground landfills is an issue of extreme engineering interest, and the proper implementation of the corresponding analyses requires dealing with several uncertainties related mainly to the special features of such large-scale geostructures. This study aims at providing an insight into the role of these parameters on the development of the potential failure modes that may take place during a seismic event. Additionally, the different failure modes are compared with respect to their seismic instability potential. Furthermore, an insight is provided on phenomena related to the simultaneous generation of more than one failure surfaces within the landfill. This is examined by developing a simple model based on the Newmark's sliding-block approach. Results indicate that the circular surfaces may provide a more critical mode of failure than the base sliding. © 2008 ASCE