957 research outputs found

    Multi-Wavelength Variability of the Synchrotron Self-Compton Model for Blazar Emission

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    Motivated by recent reports of strongly correlated radio and X-ray variability in 3C279 (Grandi, etal 1995), we have computed the relative amplitudes of variations in the synchrotron flux at ν\nu and the self-Compton X-ray flux at 1 keV (R(ν)R(\nu)) for a homogeneous sphere of relativistic electrons orbiting in a tangled magnetic field. Relative to synchrotron self-Compton scattering without induced Compton scattering, stimulated scattering reduces the amplitude of R(ν)R(\nu) by as much as an order of magnitude when \tau_T \gtwid 1. When τT\tau_T varies in a fixed magnetic field, RτR_{\tau} increases monotonically from 0.01 at νo\nu_o, the self-absorption turnover frequency, to 0.50.5 at 100νo100 \nu_o. The relative amplitudes of the correlated fluctuations in the radio-mm and X-ray fluxes from 3C279 are consistent with the synchrotron self-Compton model if τT\tau_T varies in a fixed magnetic field and induced Compton scattering is the dominant source of radio opacity. The variation amplitudes are are too small to be produced by the passage of a shock through the synchrotron emission region unless the magnetic field is perpendicular to the shock front.Comment: 21 pages, 4 fig

    A review and comparative study of release coatings for optimised abhesion in resin transfer moulding applications

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    In this study, a number of abhesion promoting coatings were considered in terms of their physicochemical and release properties. The techniques used to further this study include; FEGSEM, AFM, profilometry, AFM, XPS, AES, SSIMS, FTIR and contact angle analysis for coating physical and chemical characterisation along with PF-AFM and other adhesion and mechanical tests to determine surface release properties. These coatings were applied to metal substrates and were based upon silicone, fluoropolymer or metal-PTFE composite chemistry, all being potentially useful as release films for resin transfer moulding (RTM) applications. The semi-permanent Frekote B15/710 NC mould release coating system, which is based on PDMS, proved extremely effective in terms of release against a cured epoxide applied under pressure. Although fluoroalkylsilane coatings offer a number of technological advantages for release applications they generally produce very thin coatings which conform any existing surface topography and adhesion through mechanical interlocking occurs. The commercial PTFE-based coatings were found to provide poor release properties due to the presence of surface microcracks which allowed epoxide penetration when cured under elevated pressure and temperature. Electroless Ni/PTFE composite coatings comprise hard nickel-phosphorus matrix containing a very fine dispersion of PTFE particles. The matrix proved sufficiently robust for industrial applications and the low friction and surface energy provided by the embedded PTFE combined with macroscopic scale surface roughness provided efficient mould release

    PI3Kgamma drives priming and survival of autoreactive CD4(+) T cells during experimental autoimmune encephalomyelitis

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    The class IB phosphoinositide 3-kinase γ enzyme complex (PI3Kc) functions in multiple signaling pathways involved in leukocyte activation and migration, making it an attractive target in complex human inflammatory diseases including MS. Here, using pik3cg2/2 mice and a selective PI3Kc inhibitor, we show that PI3Kc promotes development of experimental autoimmune encephalomyelitis (EAE). In pik3cg2/2 mice, EAE is markedly suppressed and fewer leukocytes including CD4+ and CD8+ T cells, granulocytes and mononuclear phagocytes infiltrate the CNS. CD4+ T cell priming in secondary lymphoid organs is reduced in pik3cg2/2 mice following immunisation. This is attributable to defects in DC migration concomitant with a failure of full T cell activation following TCR ligation in the absence of p110c. Together, this results in suppressed autoreactive T cell responses in pik3cg2/2 mice, with more CD4+ T cells undergoing apoptosis and fewer cytokineproducing Th1 and Th17 cells in lymphoid organs and the CNS. When administered from onset of EAE, the orally active PI3Kc inhibitor AS605240 caused inhibition and reversal of clinical disease, and demyelination and cellular pathology in the CNS was reduced. These results strongly suggest that inhibitors of PI3Kc may be useful therapeutics for MS.Iain Comerford, Wendel Litchfield, Ervin Kara and Shaun R. McCol

    Mesothelial Cell HIF1 alpha Expression Is Metabolically Downregulated by Metformin to Prevent Oncogenic Tumor-Stromal Crosstalk

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    The tumor microenvironment (TME) plays a pivotal role in cancer progression, and, in ovarian cancer (OvCa), the primary TME is the omentum. Here, we show that the diabetes drug metformin alters mesothelial cells in the omental microenvironment. Metformin interrupts bidirectional signaling between tumor and mesothelial cells by blocking OvCa cell TGF-beta signaling and mesothelial cell production of CCL2 and IL-8. Inhibition of tumor-stromal crosstalk by metformin is caused by the reduced expression of the tricarboxylic acid (TCA) enzyme succinyl CoA ligase (SUCLG2). Through repressing this TCA enzyme and its metabolite, succinate, metformin activated prolyl hydroxylases (PHDs), resulting in the degradation of hypoxia-inducible factor 1 alpha (HIF1 alpha) in mesothelial cells. Disruption of HIF1 alpha-driven IL-8 signaling in mesothelial cells by metformin results in reduced OvCa invasion in an organotypic 3D model. These findings indicate that tumor-promoting signaling between mesothelial and OvCa cells in the TME can be targeted using metformin

    The Effects of Periodically Gapped Time Series on Cross-correlation Lag Determinations

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    The three bright TeV blazars Mrk 421, Mrk 501 and PKS 2155-404 are highly variable in synchrotron X-ray emission. In particular, these sources may exhibit variable time lags between flux variations at different X-ray energy bands. However, there are a number of issues that may significantly bias lag determinations. Edelson et al. (2001) recently proposed that the lags on timescales of hours, discovered by ASCA and BeppoSAX, could be an artifact of periodic gaps in the light curves introduced by the Earth occultation every \~1.6 hr. Using Monte Carlo simulations, in this paper we show that the lags over timescales of hours can not be the spurious result of periodic gaps, while periodic gaps indeed introduces uncertainty larger than what present in the evenly sampled data. The results also show that time lag estimates can be substantially improved by using evenly sampled light curves with large lag to bin-size ratio. Furthermore, we consider an XMM-Newton observation without interruptions and re-sample the light curves using the BeppoSAX observing windows, and then repeat the same cross correlation function (CCF) analysis on both the real and fake data. The results also show that periodic gaps in the light curves do not significantly distort the CCF characters, and indeed the CCF peak ranges of the real and fake data overlap. Therefore, the lags discovered by ASCA and BeppoSAX are not due to periodic gaps in the light curves.Comment: 13 pages, 6 figures, accepted for publication in Ap

    Volume Characteristics of Landslides Triggered by the MW 7.8 2016 Kaikōura Earthquake, New Zealand, Derived From Digital Surface Difference Modeling

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    We use a mapped landslide inventory coupled with a 2‐m resolution vertical difference model covering an area of 6,875 km2 to accurately constrain landslide volume‐area relationships. We use the difference model to calculate the source volumes for landslides triggered by the MW 7.8 Kaikōura, New Zealand, earthquake of 14 November 2016. Of the 29,519 mapped landslides in the inventory, 28,394 are within the analysis area, and of these, we have calculated the volume of 17,256 source areas that are ≥90% free of debris. Of the 28,394 landslides, about 80% are classified as soil or rock avalanches and the remainder as mainly translational slides. Our results show that both the soil avalanches and the rock avalanches, ignoring their source geology, have area to volume power‐law scaling exponents (γ) of 0.921 to 1.060 and 1.040 to 1.138, respectively. These are lower than the γ values of 1.1–1.3 (for soil) and 1.3–1.6 (for rock) reported in the literature for undifferentiated landslide types. They are, however, similar to those γ values estimated from other coseismic landslide inventories. In contrast, for 50 selected rotational, translational (planar slide surfaces), or compound slides, where much of the debris remains in the source area, we found γ values range between 1.46 and 1.47, indicating that their slide surfaces were considerably deeper than those landslides classified as avalanches. This study, like previous studies on coseismic landslides, shows that soil and rock avalanches (disrupted landslides) are the dominant landslide type triggered by earthquakes and that they tend to be shallow.Key PointsWe use a 2‐m resolution vertical difference model to estimate source volumes for 17,256 landslides with sources ≥90% free of debris triggered by the MW7.8 2016 Kaikōura EarthquakeThe model was derived by subtracting a tectonically adjusted pre‐EQ surface model from a post‐EQ model, covering an area of 6,875 km2Landslide trigger mechanism, type/failure mode, and source material are critical for accurate estimation of landslide volumes from source‐area geometriesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156166/2/jgrf21176.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156166/1/jgrf21176_am.pd

    Test result communication in primary care : clinical and office staff perspectives

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    OBJECTIVE. To understand how the results of laboratory tests are communicated to patients in primary care and perceptions on how the process may be improved. DESIGN. Qualitative study employing staff focus groups. SETTING. Four UK primary care practices. PARTICIPANTS. Staff involved in the communication of test results. FINDINGS. Five main themes emerged from the data: (i) the default method for communicating results differed between practices; (ii) clinical impact of results and patient characteristics such as anxiety level or health literacy influenced methods by which patients received their test result; (iii) which staff member had responsibility for the task was frequently unclear; (iv) barriers to communicating results existed, including there being no system or failsafe in place to determine whether results were returned to a practice or patient; (v) staff envisaged problems with a variety of test result communication methods discussed, including use of modern technologies, such as SMS messaging or online access. CONCLUSIONS. Communication of test results is a complex yet core primary care activity necessitating flexibility by both patients and staff. Dealing with the results from increasing numbers of tests is resource intensive and pressure on practice staff can be eased by greater utilization of electronic communication. Current systems appear vulnerable with no routine method of tracing delayed or missing results. Instead, practices only become aware of missing results following queries from patients. The creation of a test communication protocol for dissemination among patients and staff would help ensure both groups are aware of their roles and responsibilities

    Undertaking rapid evaluations during the COVID-19 pandemic: Lessons from evaluating COVID-19 remote home monitoring services in England

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    Introduction: Rapid evaluations can offer evidence on innovations in health and social care that can be used to inform fast-moving policy and practise, and support their scale-up according to previous research. However, there are few comprehensive accounts of how to plan and conduct large-scale rapid evaluations, ensure scientific rigour, and achieve stakeholder engagement within compressed timeframes. / Methods: Using a case study of a national mixed-methods rapid evaluation of COVID-19 remote home monitoring services in England, conducted during the COVID-19 pandemic, this manuscript examines the process of conducting a large-scale rapid evaluation from design to dissemination and impact, and reflects on the key lessons for conducting future large-scale rapid evaluations. In this manuscript, we describe each stage of the rapid evaluation: convening the team (study team and external collaborators), design and planning (scoping, designing protocols, study set up), data collection and analysis, and dissemination. / Results: We reflect on why certain decisions were made and highlight facilitators and challenges. The manuscript concludes with 12 key lessons for conducting large-scale mixed-methods rapid evaluations of healthcare services. We propose that rapid study teams need to: (1) find ways of quickly building trust with external stakeholders, including evidence-users; (2) consider the needs of the rapid evaluation and resources needed; (3) use scoping to ensure the study is highly focused; (4) carefully consider what cannot be completed within a designated timeframe; (5) use structured processes to ensure consistency and rigour; (6) be flexible and responsive to changing needs and circumstances; (7) consider the risks associated with new data collection approaches of quantitative data (and their usability); (8) consider whether it is possible to use aggregated quantitative data, and what that would mean when presenting results, (9) consider using structured processes & layered analysis approaches to rapidly synthesise qualitative findings, (10) consider the balance between speed and the size and skills of the team, (11) ensure all team members know roles and responsibilities and can communicate quickly and clearly; and (12) consider how best to share findings, in discussion with evidence-users, for rapid understanding and use. / Conclusion: These 12 lessons can be used to inform the development and conduct of future rapid evaluations in a range of contexts and settings

    Bioactivity of Argentinean Essential Oils Against Permethrin-Resistant Head Lice, Pediculus humanus capitis

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    Infestation with the head louse, Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), is one of the most common parasitic infestation of humans worldwide. Traditionally, the main treatment for control of head lice is chemical control that is based in a wide variety of neurotoxic synthetic insecticides. The repeated overuse of these products has resulted in the selection of resistant populations of head lice. Thus, plant-derived insecticides, such as the essential oils seem to be good viable alternatives as some have low toxicity to mammals and are biodegradable. We determined the insecticidal activity of 25 essential oils belonging to several botanical families present in Argentina against permethrin-resistant head lice. Significant differences in fumigant activity against head lice were found among the essential oils from the native and exotic plant species. The most effective essential oils were Cinnamomum porphyrium, followed by Aloysia citriodora (chemotype 2) and Myrcianthes pseudomato, with KT50 values of 1.12, 3.02 and 4.09; respectively. The results indicate that these essential oils are effective and could be incorporated into pediculicide formulations to control head lice infestations once proper formulation and toxicological tests are performed

    Measuring the impact of maternal critical care admission on short- and longer-term maternal and birth outcomes

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    PurposeFactors increasing the risk of maternal critical illness are rising in prevalence in maternity populations. Studies of general critical care populations highlight that severe illness is associated with longer-term physical and psychological morbidity. We aimed to compare short- and longer-term outcomes between women who required critical care admission during pregnancy/puerperium and those who did not. MethodsA cohort study including all women delivering in Scottish hospitals between 01/01/2005-31/12/2018, using national healthcare databases. The primary exposure was Intensive Care Unit (ICU) admission, whilst secondary exposures included High Dependency Unit admission. Outcomes included hospital readmission (1-year post-hospital discharge, 1-year mortality, psychiatric hospital admission, stillbirth and neonatal critical care admission). Multivariable Cox and logistic regression were used to report hazard ratios (HR) and odds ratios (OR) of association between ICU admission and outcomes. ResultsOf 762,918 deliveries, 1,449 (0.18%) women were admitted to ICU, most commonly due to post-partum haemorrhage (225, 15.5%) followed by eclampsia/pre-eclampsia (133, 9.2%). Over-half (53.8%) required mechanical ventilation. One-year hospital readmission was more frequent in women admitted to ICU compared with non-ICU populations (24.5% (n=299) vs 8.9% (n=68,029)). This association persisted after confounder adjustment (HR=1.93, 95%CI 1.33, 2.81, p&lt;0.001). Furthermore, maternal ICU admission was associated with increased 1-year mortality (HR=40.06, 95%CI 24.04,66.76, p&lt;0.001, stillbirth (OR=12.31, 95%CI 7.95,19.08,p&lt;0.001) and neonatal critical care admission (OR=6.99, 95%CI 5.64 ,8.67, p&lt;0.001) after confounder adjustment. ConclusionCritical care admission increases the risk of adverse short-term and long-term maternal, pregnancy and neonatal outcomes. Optimising long-term post-partum care may benefit maternal critical illness survivors.<br/
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