Scanning apertureless microscopy below the diffraction limit: Comparisons between theory and experiment

The exact nature of the signal in scanning apertureless microscopy techniques is the subject of much debate. We have sought to resolve this controversy by carrying out simulations and experiments on the same structures. Simulations of a model of tip–sample coupling are shown to exhibit features that are in agreement with experimental observations at dimensions below the diffraction limit. The simulation of the optical imaging process is carried out using atomic force microscope data as a topographical template and a tip–sample dipole coupling model as the source of optical signal. The simulations show a number of key fingerprints including a dependence on the polarization of the external laser source, the size of the tip, and index of refraction of the sample being imaged. The experimental results are found to be in agreement with many of the features of the simulations. We conclude that the results of the dipole coupling theory agree qualitatively with experimental data and that apertureless microscopy measures optical properties, not just topography

‘When the daily commute stops’: a long-distance commuter’s reflections on commuting and telecommuting across the COVID-19 pandemic

This article foregrounds the working experience of a knowledge worker in the United Kingdom across three years (2019-2022) that included periods of ‘lockdown’ and other social restrictions resulting from the COVID-19 pandemic. Across seven separate interview extracts, it offers a longitudinal narrative on the lived experience of substituting a workday comprising a long-distance commute by car to work ‘standard’ hours for an extended workday telecommuting from home. Over time the worker paradoxically recognises that telecommuting entails added pressures of work intensification, extensification and greater domestic responsibility but this is preferable to returning to a long-distance dissatisfying commute. The reflexive narrative reveals how he embraces the pressures of telecommuting through job crafting to re-identify as an autonomous professional and more engaged care-giving parent. The article contributes to the literature on hybrid/flexible forms of work organisation emerging from the pandemic by indicating the importance of micro-level considerations and implications for gender equality

Alterations to nuclear architecture and genome behavior in senescent cells.

The organization of the genome within interphase nuclei, and how it interacts with nuclear structures is important for the regulation of nuclear functions. Many of the studies researching the importance of genome organization and nuclear structure are performed in young, proliferating, and often transformed cells. These studies do not reveal anything about the nucleus or genome in nonproliferating cells, which may be relevant for the regulation of both proliferation and replicative senescence. Here, we provide an overview of what is known about the genome and nuclear structure in senescent cells. We review the evidence that nuclear structures, such as the nuclear lamina, nucleoli, the nuclear matrix, nuclear bodies (such as promyelocytic leukemia bodies), and nuclear morphology all become altered within growth-arrested or senescent cells. Specific alterations to the genome in senescent cells, as compared to young proliferating cells, are described, including aneuploidy, chromatin modifications, chromosome positioning, relocation of heterochromatin, and changes to telomeres

Charge storage in CeO2/Si/CeO2/Si(111) structures by electrostatic force microscopy

An electrostatic force microscope was used to write and image localized dots of charge in a double barrier CeO2/Si/CeO2/Si(111) structure. By applying a relatively large tip voltage and reducing the tip to sample separation to 3–5 nm, charge dots 60–200 nm full width at half maximum of both positive and negative charge have been written. The total stored charge is found to be Q = ±(20–200)e per charge dot. These dots of charge are shown to be stable over periods of time greater than 24 h, with an initial charge decay time constant of tau ~ 9.5 h followed by a period of much slower decay with tau > 24 h. The dependence of dot size and total stored charge on various writing parameters such as tip writing bias, tip to sample separation, and write time is examined

Interphase chromosome positioning in in vitro porcine cells and ex vivo porcine tissues

Copyright @ 2012 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and 85 reproduction in any medium, provided the original author and source are credited. The article was made available through the Brunel University Open Access Publishing Fund.BACKGROUND: In interphase nuclei of a wide range of species chromosomes are organised into their own specific locations termed territories. These chromosome territories are non-randomly positioned in nuclei which is believed to be related to a spatial aspect of regulatory control over gene expression. In this study we have adopted the pig as a model in which to study interphase chromosome positioning and follows on from other studies from our group of using pig cells and tissues to study interphase genome re-positioning during differentiation. The pig is an important model organism both economically and as a closely related species to study human disease models. This is why great efforts have been made to accomplish the full genome sequence in the last decade. RESULTS: This study has positioned most of the porcine chromosomes in in vitro cultured adult and embryonic fibroblasts, early passage stromal derived mesenchymal stem cells and lymphocytes. The study is further expanded to position four chromosomes in ex vivo tissue derived from pig kidney, lung and brain. CONCLUSIONS: It was concluded that porcine chromosomes are also non-randomly positioned within interphase nuclei with few major differences in chromosome position in interphase nuclei between different cell and tissue types. There were also no differences between preferred nuclear location of chromosomes in in vitro cultured cells as compared to cells in tissue sections. Using a number of analyses to ascertain by what criteria porcine chromosomes were positioned in interphase nuclei; we found a correlation with DNA content.This study is partly supported by Sygen International PLC

Elevated expression of artemis in human fibroblast cells is associated with cellular radiosensitivity and increased apoptosis

Copyright @ 2012 Nature Publishing GroupThis article has been made available through the Brunel Open Access Publishing Fund.Background: The objective of this study was to determine the molecular mechanism(s) responsible for cellular radiosensitivity in two human fibroblast cell lines 84BR and 175BR derived from two cancer patients. Methods: Clonogenic assays were performed following exposure to increasing doses of gamma radiation to confirm radiosensitivity. γ-H2AX foci assays were used to determine the efficiency of DNA double strand break (DSB) repair in cells. Quantitative-PCR (Q-PCR) established the expression levels of key DNA DSB repair proteins. Imaging flow cytometry using Annexin V-FITC was used to compare artemis expression and apoptosis in cells. Results: Clonogenic cellular hypersensitivity in the 84BR and 175BR cell lines was associated with a defect in DNA DSB repair measured by the γ-H2AX foci assay. Q-PCR analysis and imaging flow cytometry revealed a two-fold overexpression of the artemis DNA repair gene which was associated with an increased level of apoptosis in the cells before and after radiation exposure. Over-expression of normal artemis protein in a normal immortalised fibroblast cell line NB1-Tert resulted in increased radiosensitivity and apoptosis. Conclusion: We conclude elevated expression of artemis is associated with higher levels of DNA DSB, radiosensitivity and elevated apoptosis in two radio-hypersensitive cell lines. These data reveal a potentially novel mechanism responsible for radiosensitivity and show that increased artemis expression in cells can result in either radiation resistance or enhanced sensitivity.This work was supported in part by The Vidal Sassoon Foundation USA. This article is made available through the Brunel Open Access Publishing Fund

Designing for Dissemination: Lessons in Message Design from 1-2-3 Pap

Despite a large number of evidence-based health communication interventions tested in private, public, and community health settings, there is a dearth of research on successful secondary dissemination of these interventions to other audiences. This article presents the case study of 1-2-3 Pap, a health communication intervention to improve human papillomavirus (HPV) vaccination uptake and Pap testing outcomes in Eastern Kentucky, and explores strategies used to disseminate this intervention to other populations in Kentucky, North Carolina, and West Virginia. Through this dissemination project, we identified several health communication intervention design considerations that facilitated our successful dissemination to these other audiences; these intervention design considerations include (a) developing strategies for reaching other potential audiences, (b) identifying intervention message adaptations that might be needed, and (c) determining the most appropriate means or channels by which to reach these potential future audiences. Using 1-2-3 Pap as an illustrative case study, we describe how careful planning and partnership development early in the intervention development process can improve the potential success of enhancing the reach and effectiveness of an intervention to other audiences beyond the audience for whom the intervention messages were originally designed

The radial arrangement of the human chromosome 7 in the lymphocyte cell nucleus is associated with chromosomal band gene density

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ Springer-Verlag 2008.In the nuclei of human lymphocytes, chromosome territories are distributed according to the average gene density of each chromosome. However, chromosomes are very heterogeneous in size and base composition, and can contain both very gene-dense and very gene-poor regions. Thus, a precise analysis of chromosome organisation in the nuclei should consider also the distribution of DNA belonging to the chromosomal bands in each chromosome. To improve our understanding of the chromatin organisation, we localised chromosome 7 DNA regions, endowed with different gene densities, in the nuclei of human lymphocytes. Our results showed that this chromosome in cell nuclei is arranged radially with the gene-dense/GC-richest regions exposed towards the nuclear interior and the gene-poorest/GC-poorest ones located at the nuclear periphery. Moreover, we found that chromatin fibres from the 7p22.3 and the 7q22.1 bands are not confined to the territory of the bulk of this chromosome, protruding towards the inner part of the nucleus. Overall, our work demonstrates the radial arrangement of the territory of chromosome 7 in the lymphocyte nucleus and confirms that human genes occupy specific radial positions, presumably to enhance intra- and inter-chromosomal interaction among loci displaying a similar expression pattern, and/or similar replication timing

Telomere disruption results in non-random formation of de novo dicentric chromosomes involving acrocentric human chromosomes

Copyright: © 2010 Stimpson et al.Genome rearrangement often produces chromosomes with two centromeres (dicentrics) that are inherently unstable because of bridge formation and breakage during cell division. However, mammalian dicentrics, and particularly those in humans, can be quite stable, usually because one centromere is functionally silenced. Molecular mechanisms of centromere inactivation are poorly understood since there are few systems to experimentally create dicentric human chromosomes. Here, we describe a human cell culture model that enriches for de novo dicentrics. We demonstrate that transient disruption of human telomere structure non-randomly produces dicentric fusions involving acrocentric chromosomes. The induced dicentrics vary in structure near fusion breakpoints and like naturally-occurring dicentrics, exhibit various inter-centromeric distances. Many functional dicentrics persist for months after formation. Even those with distantly spaced centromeres remain functionally dicentric for 20 cell generations. Other dicentrics within the population reflect centromere inactivation. In some cases, centromere inactivation occurs by an apparently epigenetic mechanism. In other dicentrics, the size of the alpha-satellite DNA array associated with CENP-A is reduced compared to the same array before dicentric formation. Extrachromosomal fragments that contained CENP-A often appear in the same cells as dicentrics. Some of these fragments are derived from the same alpha-satellite DNA array as inactivated centromeres. Our results indicate that dicentric human chromosomes undergo alternative fates after formation. Many retain two active centromeres and are stable through multiple cell divisions. Others undergo centromere inactivation. This event occurs within a broad temporal window and can involve deletion of chromatin that marks the locus as a site for CENP-A maintenance/replenishment.This work was supported by the Tumorzentrum Heidelberg/Mannheim grant (D.10026941)and by March of Dimes Research Foundation grant #1-FY06-377 and NIH R01 GM069514

PVP2008-61762 DESIGN AND MANUFACTURE OF WELDED PLATE SPECIMENS FOR RESIDUAL STRESS EXPERIMENTS

ABSTRACT A long-term UK research programme has been established in order to improve the understanding of thermo-mechanical behaviour and residual stresses generated in pressure vessel steel welds as well as developing finite element (FE) welding simulation methods. The production of representative test specimens is an important element of this research project, since quality measurement data are needed to validate FE models. This paper describes the design, development and manufacture of welded plate specimens used for residual stress (RS) experiments. To date, research has focused mainly on developing the understanding of SA508 pressure vessel steel welds. Specimen dimensions were selected to facilitate stress measurements using a range of techniques. The philosophy adopted was to start with relatively simple 1-pass weld specimens and gradually increase the complexity to multi-pass groove welds in plates. Simple 1-pass weld specimens were generally designed to investigate the effect of welding parameters on thermomechanical behaviour, such as heat-affected zone (HAZ) microstructures and phase transformations. Later specimens are more representative of multi-pass power plant welds. They are being used to study material thermal cyclic hardening/softening behaviour. Other issues of concern are also being investigated, such as the effect of restraint during welding on RS and the effectiveness of post weld heat treatment (PWHT). Specimens were also designed to study peak stresses arising at bead stop/start positions and whether such peak stresses are annealed in overlaying additional weld metal. These investigations were performed on multi-pass groove welds in both austenitic and ferritic steel plates. Practical issues encountered during welding trials are discussed, including plate distortion and magnetisation of the ferritic steel plates. Information is also provided about welding temperature measurements and metallurgical examinations