Modeling Stem/Progenitor Cell-Induced Neovascularization and\ud Oxygenation around Solid Implants

Tissue engineering constructs and other solid implants with biomedical applications, such as drug delivery devices or bioartificial organs, need oxygen (O2) to function properly. To understand better the vascular integration of such devices, we recently developed a novel model sensor containing O2-sensitive crystals, consisting of a polymeric capsule limited by a nano-porous filter. The sensor was implanted in mice with hydrogel alone (control) or hydrogel embedded with mouse CD117/c-kit+ bone marrow progenitor cells (BMPC) in order to stimulate peri-implant neovascularization. The sensor provided local partial O2 pressure (pO2) using non-invasive electron paramagnetic resonance (EPR) signal measurements. A consistently higher level of per-implant oxygenation was observed in the cell-treatment case as compared to the control over a 10-week period. In order to provide a mechanistic explanation of these experimental observations, we present in this paper a mathematical model, formulated as a system of coupled partial differential equations, that simulates peri-implant vascularization. In the control case, vascularization is considered to be the result of a Foreign Body Reaction (FBR) while in the cell-treatment case, adipogenesis in response to paracrine stimuli produced by the stem cells is assumed to induce neovascularization. The model is validated by fitting numerical predictions of local pO2 to measurements from the implanted sensor. The model is then used to investigate further the potential for using stem cell treatment to enhance the vascular integration of biomedical implants. We thus demonstrate how mathematical modeling combined with experimentation can be used to infer how vasculature develops around biomedical implants in control and stem celltreated cases

"After Tocqueville – the Curious Adventures of Bernard-Henri Lévy and Don Watson"

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"One Day in the Life of David Hicks"

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Mr Galt Goes To Washington

Two recently published oral histories highlight the long-term trend concerning the mainstreaming of Objectivism, the political and economic ideas of the libertarian conservative writer and ideologue, Ayn Rand. Scott McConnell’s sympathetic interview collection focuses on supporters and acquaintances from Rand’s active period in the 1960s and 1970s. These supporters and acquaintances include former Australian Prime Minister, Malcolm Fraser, who provides McConnell with his considered views concerning Rand. Gary Weiss’s critical interview collection focusses on her more recent supporters, with one displeased and insightful interviewee to be found in both collections. Weiss’s collection reveals the role played by Objectivists in galvanizing the focus of the populist Tea Party movement. Both oral histories reveal the role played by the media and popular culture in mainstreaming Rand’s views. The review ends by comparing Randolph Stow’s socially responsive individualism as described in his novel 'Tourmaline' with Rand’s transactional individualism as described in 'Atlas Shrugged.

" Tocqueville in a Conservative World"

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The Cyclic Flats of a qq-Matroid

In this paper we develop the theory of cyclic flats of $q$-matroids. We show that the lattice of cyclic flats, together with their ranks, uniquely determines a $q$-matroid and hence derive a new $q$-cryptomorphism. We introduce the notion of $\mathbb{F}_{q^m}$-independence of an $\mathbb{F}_q$-subspace of $\mathbb{F}_q^n$ and we show that $q$-matroids generalize this concept, in the same way that matroids generalize the notion of linear independence of vectors over a given field

A questionnaire study of the negative outcomes for UK health professional volunteers in low and middle income countries

© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. INTRODUCTION: Past research has reported considerable benefits of international health professional volunteering for British healthcare professionals; however, there are also some negative outcomes reported. Negative outcomes reportedly happen on a personal, professional and organisational level. However, there is little evidence of the frequency they might occur. METHODS: We aimed to understand what the negative outcomes of health professional volunteering in low-income and middle-income countries were, and how frequently they occurred, in an opportunistic sample of UK health professionals. We used a questionnaire developed using potential negative outcomes reported in the peer-reviewed papers. We conducted secondary analysis on cross-sectional questionnaire data from 222 healthcare professionals. RESULTS: This research provides an indication of the frequency that negative outcomes might occur. Post hoc analyses revealed that some outcomes were experienced by the majority of health professional volunteers, for example, lack of formal recognition (131/169, 78%) and financial cost (92/169, 68%). While others happened less, for example, a reliance on agency or locum work (12/169, 7%) and loss of pension (31/169, 18%). CONCLUSION: The outcomes reported in this research quantify some of the concerns that have been raised in previous literature. Negative outcomes might be associated with certain features of volunteering and further research is needed to prospectively compare different features. Organisers of volunteering opportunities should be aware of the potential negative outcomes and engage with the research into negative outcomes to generate and apply findings about minimising potential negative outcomes, carefully balancing these against the needs of the host country

Seasonal persistence of circulation anomalies in the Southern Hemisphere stratosphere, and its implications for the troposphere

Previous studies have highlighted an important organising influence of the seasonal Southern Hemisphere stratospheric vortex breakdown on the large-scale stratospheric and tropospheric circulation. The present study extends this work by considering the statistical predictability of the stratospheric vortex breakdown event, using re-analysis data. Perturbations to the winter stratospheric vortex are shown to persist into austral spring, and to lead to a shift in the statistics of the breakdown event during austral summer. This is interpreted as evidence for the potential for seasonal predictability of the vortex breakdown event in the stratosphere. Coupled variability between the stratosphere and troposphere is then considered. The semi-annual oscillation of the tropospheric mid-latitude jet is discussed and evidence for a connection between this behaviour and variations in the stratosphere is presented. Based on this connection, an argument is made for the concomitant potential for seasonal predictability in the troposphere, assuming knowledge of the stratospheric initial state. Combining these various results, a non-stationary, regime-based perspective of large-scale extra-tropical Southern Hemisphere circulation variability between late winter and summer is proposed. The implications of this perspective for some previous studies involving Annular Modes of the circulation are discussed. In particular, the long Annular Mode timescales during austral spring and summer should not be interpreted as an increased persistence of perturbations to some slowly varying seasonal cycle, but instead reflect a phase shift of the seasonal cycle induced by stratospheric variability

Interest rate co-movements, global factors and the long end of the term spread

The disconnect between rising short and low long interest rates has been a distinctive feature of the 2000s. Both research and policy circles have argued that international forces, such as global monetary policy (e.g. Rogoff, 2006); international business cycles (e.g. Borio and Filardo, 2007); or a global savings glut (e.g Bernanke, 2005) may be responsible. In this paper, we employ recent advances in panel data econometrics to document the disconnect and link it explicitly to the existence of a global latent factor that dominates the long end of the term spread for the recent period; the saving glut story emerges as the most likely contender for the global factor

B Cells Activated in Lymph Nodes in Response to Ultraviolet Irradiation or by Interleukin-10 Inhibit Dendritic Cell Induction of Immunity

Ultraviolet (UV) radiation suppresses systemic immunity. We explored these cellular mechanisms by exposing mice to systemically immunosuppressive doses of UV radiation and then analyzing cell phenotype and function in the lymphoid organs. Although UV radiation increased total cell number in the draining lymph nodes (DLN), it did not alter the activation state of dendritic cells (DC). Rather, UV radiation selectively activated lymph node B cells, with these cells being larger and expressing higher levels of both anti-major histocompatibility complex II and B220 but not co-stimulatory molecules. This phenotype resembled that of a B cell geared toward immune tolerance. To test whether UV radiation-activated B cells were responsible for immunosuppression, DC and B cells were conjugated to antigen ex vivo and transferred into naïve hosts. Although DC by themselves activated T cells, when the B cells from UV radiation-irradiated mice were co-injected with DC, they suppressed DC activation of immunity. Interleukin (IL)-10-activated B cells also suppressed DC induction of immunity, suggesting that IL-10 may be involved in this suppressive effect of UV radiation. These results demonstrate a new mechanism of UV radiation immunosuppression whereby UV radiation activates B cells in the skin-DLN that can suppress DC activation of T cell-mediated immunity