987 research outputs found

    Discussion of Recent Decisions

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    One-Liners

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    One-Liners from P.T. Borgia, J. Irelan and E.U. Selker, and B.C. Turner and A. Fairfiel

    Waves on the dusk flank boundary layer during very northward interplanetary magnetic field conditions: Observations and simulation

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95617/1/jgra18641.pd

    On the multispacecraft determination of periodic surface wave phase speeds and wavelengths

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    Observations of surface waves on the magnetopause indicate a wide range of phase velocities and wavelengths. Their multispacecraft analysis allows a more precise determination of wave characteristics than ever before and reveal shortcomings of approximations to the phase speed that take a predetermined fraction of the magnetosheath speed or the average flow velocity in the boundary layer. We show that time lags between two or more spacecraft can give a qualitative upper estimate, and we confirm the unreliability of flow approximations often used by analyzing a few cases. Using two‐point distant magnetic field observations and spectral analysis of the tailward magnetic field component, we propose an alternative method to estimate the wavelength and phase speed at a single spacecraft from a statistical fit to the data at the other site

    Meta-analysis and Meta-regression of Survival After Liver Transplantation for Unresectable Perihilar Cholangiocarcinoma

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    Objective: To systematically review studies reporting survival data following neoadjuvant chemoradiation and orthotopic liver transplantation (NCR-OLT) for unresectable perihilar cholangiocarcinoma (pCC). Background: Despite survival improvements for other cancers, the prognosis of pCC remains dismal. Since publication of the Mayo protocol in 2000, increasing numbers of series globally are reporting outcomes after NCR-OLT. Methods: MEDLINE, EMBASE, Scopus, and Web of Science databases were searched from January 2000 to February 2019. A meta-analysis of proportions was conducted, pooling 1, 3-, and 5-year overall survival and recurrence rates following NCR-OLT across centers. Per protocol and intention to treat data were interrogated. Meta-regression was used to evaluate PSC as a confounder affecting survival. Results: Twenty studies comprising 428 patients were eligible for analysis. No RCTs were retrieved; the majority of studies were noncomparative cohort studies. The pooled 1, 3-, and 5-year overall survival rates following OLT without neoadjuvant therapy were 71.2% (95% CI 62.2%–79.4%), 48.0% (95% CI 35.0%–60.9%), and 31.6% (95% CI 23.1%–40.7%). These improved to 82.8% (95% CI 73.0%–90.8%), 65.5% (95% CI 48.7%–80.5%), and 65.1% (95% CI 55.1%–74.5%) if neoadjuvant chemoradiation was completed. Pooled recurrence after 3 years was 24.1% (95% CI 17.9%–30.9%) with neoadjuvant chemoradiation, 51.7% (95% CI 33.8%–69.4%) without. Conclusions: In unresectable pCC, NCR-OLT confers long-term survival in highly selected patients able to complete neoadjuvant chemoradiation followed by transplantation. PSC patients appear to have the most favorable outcomes. A high recurrence rate is of concern when considering extending national graft selection policy to pCC.publishedVersio

    Pressure balance at the magnetopause: Experimental studies

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    The pressure balance at the magnetopause is formed by magnetic field and plasma in the magnetosheath, on one side, and inside the magnetosphere, on the other side. In the approach of dipole earth's magnetic field configuration and gas-dynamics solar wind flowing around the magnetosphere, the pressure balance predicts that the magnetopause distance R depends on solar wind dynamic pressure Pd as a power low R ~ Pd^alpha, where the exponent alpha=-1/6. In the real magnetosphere the magnetic filed is contributed by additional sources: Chapman-Ferraro current system, field-aligned currents, tail current, and storm-time ring current. Net contribution of those sources depends on particular magnetospheric region and varies with solar wind conditions and geomagnetic activity. As a result, the parameters of pressure balance, including power index alpha, depend on both the local position at the magnetopause and geomagnetic activity. In addition, the pressure balance can be affected by a non-linear transfer of the solar wind energy to the magnetosheath, especially for quasi-radial regime of the subsolar bow shock formation proper for the interplanetary magnetic field vector aligned with the solar wind plasma flow.Comment: 8 pages, 2 figure

    Stepwise tailward retreat of magnetic reconnection: THEMIS observations of an auroral substorm

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    Auroral stepwise poleward expansions were clarified by investigating a multiple‐onset substorm that occurred on 27 February 2009. Five successive auroral brightenings were identified in all‐sky images, occurring at approximately 10 min intervals. The first brightening was a faint precursor. The second brightening had a wide longitude; thus, it represented the Akasofu substorm onset. Other brightenings expanded poleward; thus, they were interpreted to be auroral breakups. These breakups occurred stepwise; that is, later breakups were initiated at higher latitudes. Corresponding reconnection signatures were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations between 8 and 24 RE down the magnetotail. The Akasofu substorm onset was not accompanied by a clear reconnection signature in the tail. In contrast, the three subsequent auroral breakups occurred simultaneously (within a few minutes) with three successive fast flows at 24 RE; thus, these were interpreted to be associated with impulsive reconnection episodes. These three fast flows consisted of a tailward flow and two subsequent earthward flows. The flow reversal at the second breakup indicated that a tailward retreat of the near‐Earth reconnection site occurred during the substorm expansion phase. In addition, the earthward flow at the third breakup was consistent with the classic tailward retreat near the end of the expansion phase; therefore, the tailward retreat is likely to have occurred in a stepwise manner. We interpreted the stepwise characteristics of the tailward retreat and poleward expansion to be potentially associated by a stepwise magnetic flux pileup.Key PointsAuroral stepwise poleward expansions were associated with reconnection stepwise tailward retreatThis spatially stepwise association is consequence of magnetic flux pileupThe stepwise association resolved objections to the Hones poleward leap conceptPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146463/1/jgra52608.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146463/2/jgra52608_am.pd

    Direct Dark Matter Search using CCDs

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    There is currently vast evidence for Dark Matter (DM) from astronomical observations. However, in spite of tremendous efforts by large experimental groups, there is no confirmed direct detection of the dark matter in our galaxy. Recent experimental results and theoretical developments suggest the possibility of a DM particle with mass below 10 GeV, such a particle would escape most of the direct searches due to the large thresholds for the detection of nuclear recoils typically used. In this work we study the possibility of a new Dark Matter search with an unprecedented low threshold for the detection of nuclear recoils using high-resistivity CCD detectors (hr-CCD). Due to their extremely low readout noise and the relatively large active mass, these detectors present a unique opportunity in this field.Comment: paper presented at the Taup2009 Conferenc

    Clinical effectiveness and cost-effectiveness of pegvisomant for the treatment of acromegaly: a systematic review and economic evaluation

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    Background: Acromegaly, an orphan disease usually caused by a benign pituitary tumour, is characterised by hyper-secretion of growth hormone (GH) and insulin-like growth factor I (IGF-1). It is associated with reduced life expectancy, cardiovascular problems, a variety of insidiously progressing detrimental symptoms and metabolic malfunction. Treatments include surgery, radiotherapy and pharmacotherapy. Pegvisomant (PEG) is a genetically engineered GH analogue licensed as a third or fourth line option when other treatments have failed to normalise IGF-1 levels. Methods: Evidence about effectiveness and cost-effectiveness of PEG was systematically reviewed. Data were extracted from published studies and used for a narrative synthesis of evidence. A decision analytical economic model was identified and modified to assess the cost-effectiveness of PEG. Results: One RCT and 17 non-randomised studies were reviewed for effectiveness. PEG substantially reduced and rapidly normalised IGF-1 levels in the majority of patients, approximately doubled GH levels, and improved some of the signs and symptoms of the disease. Tumour size was unaffected at least in the short term. PEG had a generally safe adverse event profile but a few patients were withdrawn from treatment because of raised liver enzymes. An economic model was identified and adapted to estimate the lower limit for the cost-effectiveness of PEG treatment versus standard care. Over a 20 year time horizon the incremental cost-effectiveness ratio was pound81,000/QALY and pound212,000/LYG. To reduce this to pound30K/QALY would require a reduction in drug cost by about one third. Conclusion: PEG is highly effective for improving patients' IGF-1 level. Signs and symptoms of disease improve but evidence is lacking about long term effects on improved signs and symptoms of disease, quality of life, patient compliance and safety. Economic evaluation indicated that if current standards (UK) for determining cost-effectiveness of therapies were to be applied to PEG it would be considered not to represent good value for money
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