Component test facilities for marine renewable energy converters

This paper describes how the PRIMaRE group at University Exeter is engaging in the establishment of appropriate reliability methods suitable for application to marine renewable devices with a key area being the production of suitable failure rate data for the marine renewable energy industry. This activity seeks to mitigate uncertainties and cost implications associated with the reliability assessment of marine energy converters (MECs) due to an omnipresent lack of applicable failure rate data. The capability of two facilities, namely i) the South Western Mooring Test Facility (SWMTF) and ii) the Dynamic Marine Component Test facility (DMaC), to perform specimen and accelerated component testing is discussed. A case study, using data from wave tank tests and numerical simulations performed for the SWMTF, serves to illustrate how evidence of component reliability under operational conditions could be provided.The authors would like to acknowledge the support of the South West Regional Development Agency through the PRIMaRE institution. They would also like to acknowledge the European Community's Sixth Framework Programme HYDRALAB III, Contract no. 022441 (RII3). The second author would like to acknowledge the funding support from the Engineering and Physical Sciences Research Council (EPSRC) under the SUPERGEN Marine Doctoral Programme. Thanks also to Orcina for provision of their Orcaflex software

Immortalized, premalignant epithelial cell populations contain long-lived, label-retaining cells that asymmetrically divide and retain their template DNA

Abstract Introduction During selective segregation of DNA, a cell asymmetrically divides and retains its template DNA. Asymmetric division yields daughter cells whose genome reflects that of the parents, simultaneously protecting the parental cell from genetic errors that may occur during DNA replication. We hypothesized that long-lived epithelial cells are present in immortal, premalignant cell populations, undergo asymmetric division, retain their template DNA strands, and cycle both during allometric growth and during pregnancy. Methods The glands of 3-week-old immune-competent Balb/C female mice were used intact or cleared of host epithelium and implanted with ductal-limited, lobule-limited, or alveolar-ductal progenitor cells derived from COMMA-D1 pre-malignant epithelial cells. 5-Bromo-2-deoxyuridine (5-BrdU) was administered to identify those cells that retain their template DNA. Nulliparous mice were then either injected with [3H]-thymidine (3H-TdR) to distinguish 5-BrdU label-retaining cells that enter the cell cycle and euthanized, or mated, injected with 3H-TdR, and euthanized at various days after coitus. Sections were stained for estrogen receptor-α (ER-α) or progesterone receptor (PR) with immunohistochemistry. Cells labeled with both 5-BrdU and 3H-TdR were indicative of label-retaining epithelial cells (LRECs). Results Cells that retained a 5-BrdU label and cells labeled with [3H]-thymidine were found in all mice and were typically detected along the branching epithelium of mature mouse mammary glands. Cells containing double-labeled nuclei (LRECs) were found in the intact mammary glands of both pregnant and nulliparous mice, and in mammary glands implanted with premalignant cells. Double-labeled cells (3H-TdR/5-BrdU) represent a small portion of cells in the mammary gland that cycle and retain their template DNA (5-BrdU). Some label-retaining cells were also ER-α or PR positive. LRECs distributed their second label (3H-TdR) to daughter cells, and this effect persisted during pregnancy. LRECs, and small focal hyperplasia, were found in all immortalized premalignant mammary-implant groups. Conclusions The results indicate that a subpopulation of long-lived, label-retaining epithelial cells (LRECs) is present in immortal premalignant cell populations. These LRECs persist during pregnancy, retain their original DNA, and a small percentage express ER-α and PR. We speculate that LRECs in premalignant hyperplasia represent the long-lived (memory) cells that maintain these populations indefinitely.Peer Reviewe

Flowbec

publication-status: UnpublishedThis document provides an overview of the resources available for the description of the natural environment at the Wave Hub site, and surrounding region. It aims to provide the reader with an understanding of the mechanisms that have led to the collection of the data resources, and details on how to access them. Detailed information for key research areas is then presented. The document does not aim to provide results of the data collection and analysis, and the reader is referred to the data sources reviewed.NERC FLOWBE

Mathematics students' conceptions of mathematics

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Calculations of air-guided modes in photonic crystal fibers using the multipole method

We demonstrate that a combination of multipole and Bloch methods is well suited for calculating the modes of air core photonic crystal fibers. This includes determining the reflective properties of the cladding, which is a prerequisite for the modal calculations. We demonstrate that in the presence of absorption, the modal losses can be substantially smaller than in the corresponding bulk medium. © 2001 Optical Society of America

Eigenvector sensitivity under general and structured perturbations of tridiagonal Toeplitz-type matrices

The sensitivity of eigenvalues of structured matrices under general or structured perturbations of the matrix entries has been thoroughly studied in the literature. Error bounds are available and the pseudospectrum can be computed to gain insight. Few investigations have focused on analyzing the sensitivity of eigenvectors under general or structured perturbations. The present paper discusses this sensitivity for tridiagonal Toeplitz and Toeplitz-type matrices.Comment: 21 pages, 4 figure

Re-evaluation of mammary stem cell biology based on in vivo transplantation

Over nearly half a century, transplantation methods have been employed to regenerate the mammary gland in vivo. Recent highly cited reports claim to have demonstrated the regeneration of an entire functional mammary gland from a single mammary epithelial cell. Nevertheless, re-examination of the literature on the transplantation biology of mammary gland regeneration reveals that a complex, combinatorial interaction between variously differentiated mammary epithelial cells and the mammary fat pad stroma is indispensable to this process. In the present article, these issues are reviewed and discussed to provide a greater understanding of the complexity of these multiplex interactions