Gene transfer to differentiated airway epithelia with existing viral vectors is very inefficient when they are applied to the apical surface. This largely reflects the polarized distribution of receptors on the basolateral surface. To identify new receptor-ligand interactions that might be used to redirect vectors to the apical surface, we investigated the process of infection of airway epithelial cells by human coronavirus 229E (HCoV-229E), a common cause of respiratory tract infections. Using immunohistochemistry, we found the receptor for HCoV-229E (CD13 or aminopeptidase N) localized mainly to the apical surface of airway epithelia. When HCoV-229E was applied to the apical or basolateral surface of well-differentiated primary cultures of human airway epithelia, infection primarily occurred from the apical side. Similar results were noted when the virus was applied to cultured human tracheal explants. Newly synthesized virions were released mainly to the apical side. Thus, HCoV-229E preferentially infects human airway epithelia from the apical surface. The spike glycoprotein that mediates HCoV-229E binding and fusion to CD13 is a candidate for pseudotyping retroviral envelopes or modifying other viral vectors.While gene transfer is considered the most direct means to treat or prevent the lung disease associated with cystic fibrosis, several barriers prevent the practical application of this approach (36). A problem that currently limits efficient gene transfer to airway epithelia is that the receptor in most cases is localized to the basolateral surface. This has been demonstrated for several retroviral envelopes (32, 33), adenovirus (19,31,34), and adeno-associated virus (7). Thus, the mere fact that a viral vector is derived from a respiratory pathogen does not imply that it will efficiently transduce airway epithelia via the apical surface.As a first step in identifying novel ligand-receptor interactions that might be exploited to direct vectors to the apical surface of airway epithelia, we studied the infection process of human coronavirus 229E (HCoV-229E) in well-differentiated airway epithelia. Human coronaviruses are enveloped, plusstranded RNA viruses represented by the two serologically unrelated strains, HCoV-229E and HCoV-OC43, that cause mainly upper respiratory tract infections (3, 16). Epidemiological data demonstrate that the HCoV infections are responsible for approximately one-third of common colds (17, 35). HCoV-229E contains a genomic RNA of 27,277 nucleotides, a nucleocapsid (N) protein and a lipid envelope with three major membrane proteins. The three membrane proteins are the membrane (M) glycoprotein, the envelope (E) protein, and the surface spike (S) glycoprotein (11).We selected HCoV-229E for our studies for several reasons. First, it is a common cause of respiratory infections in humans (16). Second, the viral proteins involved in cell binding and the host cell glycoprotein that serves as the receptor have been identified (20,38). Third, infection by HCoV-229E involves both binding ...

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Structural Reliability Analysis (SRA) methods have been applied to marine and offshore structures for decades. SRA has proven useful in life extension exercises and inspection planning of existing offshore structures. It is also a useful tool in code development, where the reliability level provided by the code is calculated by SRA and calibrated to a target failure probability. The current analysis methods for wellhead fatigue are associated with high sensitivity to variations in some input parameters. Some of these input parameters are difficult to assess, and sensitivity screening is often needed and the worst case is then typically used as a basis for the analysis. The degree of conservatism becomes difficult to quantify, and it is therefore equally difficult to find justification to avoid worst case assumptions. By applying SRA to the problem of wellhead fatigue, the input parameters are accounted for with their associated uncertainty given by probability distributions. In performing SRA all uncertainties are considered simultaneously, and the probability of fatigue failure is estimated and the conservatism is thereby quantified. In addition SRA also provides so-called uncertainty importance factors. These represent a relative quantification of which input parameter uncertainties contribute the most to the overall failure probability, and may serve well as guidance on where possible effort to reduce the uncertainty preferably should be made. For instance, instrumentation may be used to measure the actual structural response and thus eliminate the uncertainty that is associated with response calculations. Clearly measurements obtained from an instrumented system will have its own uncertainty. Other options could be to perform specific fatigue capacity testing or pay increased attention to logging of critical operational parameters such as the cement level in the annulus between the conductor and surface casing. This article deals with the use of measurements for fatigue life estimation. Continuous measurements of the BOP motion during the drilling operations have been obtained for a subsea well in the North Sea. These measurements are used both in conventional (deterministic) analysis and in SRA (probabilistic analysis) for fatigue in the wellhead system. From the deterministic analysis improved fatigue life results are obtained if the measured response replaces the response obtained by analysis. Furthermore, SRA is used to evaluate the appropriate magnitude of the design fatigue factor when fatigue analysis is based on measured response. It is believed that the benefit from measurements and SRA serve as an improved input to the decision making process in the event of life extension of existing subsea wells.

<p>The life extension of existing deteriorating structures requires maintenance interventions which allow partial or complete rehabilitation. However, such maintenance interventions have to be economically reasonable, that is, maintenance expenditures have to be outweighed by expected future benefits. For this purpose, cost-benefit criteria are developed herein, which not only allow to specify optimal sequences of maintenance times and rehabilitation efforts, but which also allow to determine optimal lifetimes and acceptable failure rates. Numerical examples show, that deferring decisions with respect to maintenance not only results, in general, in higher losses, but also in no longer acceptable, that is, potentially hazardous structures.</p>

In most more economically developed countries an ever growing percentage of existing structures is threatened by obsolescence in the short-to medium-term-either because of structural deficits due to deterioration, or due to functional aging. To ensure sustained serviceability and safety of these structures, maintenance interventions are utilized, which allow partial or complete structural rehabilitation. However, such maintenance interventions have to be economically reasonable, that is, maintenance expenditures spent have to be outweighed by expected future benefits. For this purpose, we propose herein a novel optimization formulation for maintenance planning based on cost-benefit criteria. The usefulness of the proposed approach lies in the fact, that it not only allows to determine optimal sequences of maintenance times, rehabilitation levels and inspection qualities, but also allows to specify economically optimal lifetimes and acceptable failure rates of structures. The modeling of structural deterioration and maintenance, as well as the setting of all relevant cost factors is discussed in detail. Numerical examples investigate the effect of imperfect execution of maintenance actions and functional aging.