160 research outputs found

    The James Webb Space Telescope Mission

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    Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4m4m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5m6.5m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

    The James Webb Space Telescope Mission

    No full text
    Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4 m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5 m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 yr, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit

    Supervised tractogram filtering using Geometric Deep Learning

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    A tractogram is a virtual representation of the brain white matter. It is composed of millions of virtual fibers, encoded as 3D polylines, which approximate the white matter axonal pathways. To date, tractograms are the most accurate white matter representation and thus are used for tasks like presurgical planning and investigations of neuroplasticity, brain disorders, or brain networks. However, it is a well-known issue that a large portion of tractogram fibers is not anatomically plausible and can be considered artifacts of the tracking procedure. With Verifyber, we tackle the problem of filtering out such non-plausible fibers using a novel fullysupervised learning approach. Differently from other approaches based on signal reconstruction and/or brain topology regularization, we guide our method with the existing anatomical knowledge of the white matter. Using tractograms annotated according to anatomical principles, we train our model, Verifyber, to classify fibers as either anatomically plausible or non-plausible. The proposed Verifyber model is an original Geometric Deep Learning method that can deal with variable size fibers, while being invariant to fiber orientation. Our model considers each fiber as a graph of points, and by learning features of the edges between consecutive points via the proposed sequence Edge Convolution, it can capture the underlying anatomical properties. The output filtering results highly accurate and robust across an extensive set of experiments, and fast; with a 12GB GPU, filtering a tractogram of 1M fibers requires less than a minute

    Tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) and pulmonary involvement in COVID-19 pneumonia

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    Background: The aim of the study was to longitudinally evaluate the association between MMP-2, MMP-9, TIMP-1 and chest radiological findings in COVID-19 patients. Methods: COVID-19 patients were evaluated based on their hospital admission (baseline) and three months after hospital discharge (T post) and were stratified into ARDS and non-ARDS groups. As a control group, healthy donors (HD) were enrolled. Results: At the baseline, compared to HD (n = 53), COVID-19 patients (n = 129) showed higher plasma levels of MMP-9 (p < 0.0001) and TIMP-1 (p < 0.0001) and the higher plasma activity of MMP-2 (p < 0.0001) and MMP-9 (p < 0.0001). In the ARDS group, higher plasma levels of MMP-9 (p = 0.0339) and TIMP-1 (p = 0.0044) and the plasma activity of MMP-2 (p = 0.0258) and MMP-9 (p = 0.0021) compared to non-ARDS was observed. A positive correlation between the plasma levels of TIMP-1 and chest computed tomography (CT) score (& rho; = 0.2302, p = 0.0160) was observed. At the T post, a reduction in plasma levels of TIMP-1 (p < 0.0001), whereas an increase in the plasma levels of MMP-9 was observed (p = 0.0088). Conclusions: The positive correlation between TIMP-1 with chest CT scores highlights its potential use as a marker of fibrotic burden. At T post, the increase in plasma levels of MMP-9 and the reduction in plasma levels of TIMP-1 suggested that inflammation and fibrosis resolution were still ongoing

    Migration rate using Fully-covered metal stent in anastomotic strictures after liver transplantation: Results from the BASALT Study Group

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    Background and study aim: The traditional endoscopic therapy of anastomotic strictures (AS) after orthotopic liver transplantation (OLT) is multiple ERCPs with insertion of an increasing number of plastic stents side-by-side. Fully covered self-expanding metal stents (cSEMS) could be a valuable option to decrease the number of procedures needed or non-responders to plastic stents. This study aims to retrospectively analyze the results of AS endoscopic treatment by cSEMS and to identify any factors associated to its success. Patients and Methods Ninety-one patients (mean age 55.9 ¬Ī 7.6 DS; 73 males) from 9 Italian transplantation centers, had a cSEMS positioned for post-OLT AS between 2007 and 2017. 49 (54%) patients were treated with cSEMS as a second-line treatment. Results All the procedures were successfully performed without with no immediate complications. After ERCP, adverse events occurred in 11% of cases (2 moderate pancreatitis, 8 cholangitis). In 49 patients (54%) cSEMSs migrated. After cSEMS removal, 46 patients (51%) needed further endoscopic (45 patients) or radiologic (1 patient) treatments to solve the AS. Lastly, 7 patients underwent surgery. Multivariable stepwise logistic regression showed that cSEMS migration was the only factor associated with further treatments (OR 2.6, 95% CI 1.0-6.6; p-value 0.03); cSEMS implantation before 12 months from OLT was associated with stent migration (OR 5.2, 95% CI 1.7-16.0; p-value 0.004). Conclusions cSEMS appears to be a safe tool to treat AS. cSEMS migration is the main limitation to its routinary implantation and needs to be prevented, probably with the use of new generation anti-migration stents

    Myocardial Fibrosis at Cardiac MRI Helps Predict Adverse Clinical Outcome in Patients with Mitral Valve Prolapse

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    Background Patients with mitral valve prolapse (MVP) may develop adverse outcomes even in the absence of mitral regurgitation or left ventricular (LV) dysfunction. Purpose To investigate the prognostic value of mitral annulus disjunction (MAD) and myocardial fibrosis at late gadolinium enhancement (LGE) cardiac MRI in patients with MVP without moderate-to-severe mitral regurgitation or LV dysfunction. Materials and Methods In this longitudinal retrospective study, 118 144 cardiac MRI studies were evaluated between October 2007 and June 2020 at 15 European tertiary medical centers. Follow-up was from the date of cardiac MRI examination to June 2020; the minimum and maximum follow-up intervals were 6 months and 156 months, respectively. Patients were excluded if at least one of the following conditions was present: cardiomyopathy, LV ejection fraction less than 40%, ischemic heart disease, congenital heart disease, inflammatory heart disease, moderate or worse mitral regurgitation, participation in competitive sport, or electrocardiogram suggestive of channelopathies. In the remainder, cardiac MRI studies were reanalyzed, and patients were included if they were aged 18 years or older, MVP was diagnosed at cardiac MRI, and clinical information and electrocardiogram monitoring were available within 3 months from cardiac MRI examination. The end point was a composite of adverse outcomes: sustained ventricular tachycardia (VT), sudden cardiac death (SCD), or unexplained syncope. Multivariable Cox regression analysis was performed. Results A total of 474 patients (mean age, 47 years ¬Ī 16 [SD]; 244 women) were included. Over a median follow-up of 3.3 years, 18 patients (4%) reached the study end point. LGE presence (hazard ratio, 4.2 [95% CI: 1.5, 11.9]; P = .006) and extent (hazard ratio, 1.2 per 1% increase [95% CI: 1.1, 1.4]; P = .006), but not MAD presence (P = .89), were associated with clinical outcome. LGE presence had incremental prognostic value over MVP severity and sustained VT and aborted SCD at baseline (area under the receiver operating characteristic curve, 0.70 vs 0.62; P = .03). Conclusion In contrast to mitral annulus disjunction, myocardial fibrosis determined according to late gadolinium enhancement at cardiac MRI was associated with adverse outcome in patients with mitral valve prolapse without moderate-to-severe mitral regurgitation or left ventricular dysfunction. ¬© RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Gerber in this issue

    Migration rate using fully covered metal stent in anastomotic strictures after liver transplantation: Results from the BASALT study group

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    Background and Study Aim The traditional endoscopic therapy of anastomotic strictures (AS) after orthotopic liver transplantation (OLT) is multiple ERCPs with the insertion of an increasing number of plastic stents side-by-side. Fully covered self-expanding metal stents (cSEMS) could be a valuable option to decrease the number of procedures needed or non-responders to plastic stents. This study aims to retrospectively analyse the results of AS endoscopic treatment by cSEMS and to identify any factors associated with its success. Patients and Methods Ninety-one patients (mean age 55.9 +/- 7.6 SD; 73 males) from nine Italian transplantation centres, had a cSEMS positioned for post-OLT-AS between 2007 and 2017. Forty-nine (54%) patients were treated with cSEMS as a second-line treatment. Results All the procedures were successfully performed without immediate complications. After ERCP, adverse events occurred in 11% of cases (2 moderate pancreatitis and 8 cholangitis). In 49 patients (54%), cSEMSs migrated. After cSEMS removal, 46 patients (51%) needed further endoscopic (45 patients) or radiological (1 patient) treatments to solve the AS. Lastly, seven patients underwent surgery. Multivariable stepwise logistic regression showed that cSEMS migration was the only factor associated with further treatments (OR 2.6, 95% CI 1.0-6.6; p value 0.03); cSEMS implantation before 12 months from OLT was associated with stent migration (OR 5.2, 95% CI 1.7-16.0; p value 0.004). Conclusions cSEMS appears to be a safe tool to treat AS. cSEMS migration is the main limitation to its routinary implantation and needs to be prevented, probably with the use of new generation anti-migration stents

    Space Weather Effects Observed in the Northern Hemisphere during November 2021 Geomagnetic Storm: The Impacts on Plasmasphere, Ionosphere and Thermosphere Systems

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    On 3 November 2021, an interplanetary coronal mass ejection impacted the Earth’s magnetosphere leading to a relevant geomagnetic storm (Kp = 8-), the most intense event that occurred so far during the rising phase of solar cycle 25. This work presents the state of the solar wind before and during the geomagnetic storm, as well as the response of the plasmasphere–ionosphere–thermosphere system in the European sector. To investigate the longitudinal differences, the ionosphere–thermosphere response of the American sector was also analyzed. The plasmasphere dynamics was investigated through field line resonances detected at the European quasi-Meridional Magnetometer Array, while the ionosphere was investigated through the combined use of ionospheric parameters (mainly the critical frequency of the F2 layer, foF2) from ionosondes and Total Electron Content (TEC) obtained from Global Navigation Satellite System receivers at four locations in the European sector, and at three locations in the American one. An original method was used to retrieve aeronomic parameters from observed electron concentration in the ionospheric F region. During the analyzed interval, the plasmasphere, originally in a state of saturation, was eroded up to two Earth’s radii, and only partially recovered after the main phase of the storm. The possible formation of a drainage plume is also observed. We observed variations in the ionospheric parameters with negative and positive phase and reported longitudinal and latitudinal dependence of storm features in the European sector. The relative behavior between foF2 and TEC data is also discussed in order to speculate about the possible role of the topside ionosphere and plasmasphere response at the investigated European site. The American sector analysis revealed negative storm signatures in electron concentration at the F2 region. Neutral composition and temperature changes are shown to be the main reason for the observed decrease of electron concentration in the American sector
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