The Experts below are selected from a list of 16056 Experts worldwide ranked by ideXlab platform
Benwei Zhang - One of the best experts on this subject based on the ideXlab platform.
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the global geometrical property of jet events in high energy nuclear collisions
European Physical Journal C, 2020Co-Authors: Shiyong Chen, Wei Dai, Shanliang Zhang, Qing Zhang, Benwei ZhangAbstract:We present the first theoretical study of medium modifications of the global geometrical pattern, i.e., transverse Sphericity ( $$S_{\perp }$$ ) distribution of jet events with parton energy loss in relativistic heavy-ion collisions. In our investigation, POWHEG + PYTHIA is employed to make an accurate description of transverse Sphericity in the p + p baseline, which combines the next-to-leading order (NLO) pQCD calculations with the matched parton shower (PS). The Linear Boltzmann Transport (LBT) model of the parton energy loss is implemented to simulate the in-medium evolution of jets. We calculate the event normalized transverse Sphericity distribution in central Pb + Pb collisions at the LHC, and give its medium modifications. An enhancement of transverse Sphericity distribution at small $$S_{\perp }$$ region but a suppression at large $$S_{\perp }$$ region are observed in A + A collisions as compared to their p + p references, which indicates that in overall the geometry of jet events in Pb + Pb becomes more pencil-like. We demonstrate that for events with 2 jets in the final-state of heavy-ion collisions, the jet quenching makes the geometry more sphere-like with medium-induced gluon radiation. However, for events with $$\ge 3$$ jets, parton energy loss in the QCD medium leads to the events more pencil-like due to jet number reduction, where less energetic jets may lose their energies and then fall off the jet selection kinematic cut. These two effects offset each other and in the end result in more jetty events in heavy-ion collisions relative to that in p + p.
Gerald D Buckberg - One of the best experts on this subject based on the ideXlab platform.
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left ventricular geometry in normal and post anterior myocardial infarction patients Sphericity index and new conicity index comparisons
European Journal of Cardio-Thoracic Surgery, 2006Co-Authors: Marisa Di Donato, Petar Dabic, Serenella Castelvecchio, Carlo Santambrogio, Jelena Brankovic, Luigi Collarini, Tammam Joussef, Alessandro Frigiola, Gerald D BuckbergAbstract:Background Anterior myocardial infarction leads a sequence of structural changes that alter the size and the shape of the left ventricle. Efforts to assess shape have been made by global left ventricular (LV) chamber analysis (Sphericity index, SI) but this analysis does not detect regional shape abnormalities like those at the apical level, which precede global ventricular dilatation. Objective The present study will introduce a new analysis of regional apical changes in 52 normal subjects and in 92 patients with previous anterior myocardial infarction. Methods All patients had transthoracic echocardiogram and multiple views were obtained (long axis, 4CH, 2CH and short axis view). From the 4CH view the long and the short axes were measured and their ratio was calculated (Sphericity index). In the same view, the apical axis length was also measured and the ratio between apical and short axis length was calculated (apical conicity index, ACI). Results Patients had all the measured parameters significantly worse than normal, except the Sphericity index which remained unchanged. Ventricular length and width increased following anterior MI but the ratio between the two measurements did not change. Conversely, apical conicity index is significantly different following anterior MI, thereby indicating anterior infarction produces a less conical shape. SI and ACI differed when correlations were made in the relationship of mitral valve function; SI correlates with the degree of mitral regurgitation (MR) and with the distance of papillary muscles, conversely ACI shows an inverse correlation with the determinants of mitral regurgitation. These observations reflect differences between apical versus global dilatation in ischemic cardiomyopathy, so that mitral function is better (lower tenting area and lower coaptation height) when the apex is markedly dilated in respect to the short axis (high conicity index). In contrast, mitral function is impaired (bigger distance between papillary muscles and higher degree of mitral regurgitation), when Sphericity index is high. Conclusions Sphericity index fails to detect regional apical shape abnormalities. To address this focal change, we introduce a simple new measure termed apical conicity index, which is abnormal in patients with myocardial infarction, and can be useful to evaluate changes induced by the subsequent surgical approach of ventricular re-shaping.
Martin Beck - One of the best experts on this subject based on the ideXlab platform.
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do normal radiographs exclude aSphericity of the femoral head neck junction
Clinical Orthopaedics and Related Research, 2009Co-Authors: Marcel Dudda, Christoph E Albers, Tallal C Mamisch, Stefan Werlen, Martin BeckAbstract:ASphericity of the femoral head-neck junction is one cause for femoroacetabular impingement of the hip. However, the aSphericity often is underestimated on conventional radiographs. This study compares the presence of aSphericity on conventional radiographs with its appearance on radial slices of magnetic resonance arthrography (MRA). We retrospectively reviewed 58 selected hips in 148 patients who underwent a surgical dislocation of the hip. To assess the circumference of the proximal femur, alpha angle and height of aSphericity were measured in 14 positions using radial slices of MRA. The hips were assigned to one of four groups depending on the appearance of the head-neck junction on anteroposterior pelvic and lateral crosstable radiographs. Group I (n = 19) was circular on both planes, Group II (n = 19) was aspheric on the crosstable view, Group III (n = 4) was aspheric on the anteroposterior view, and Group IV (n = 13) was aspheric on both views. In all four groups, the highest alpha angle was found in the anterosuperior area of the head-neck junction. Even when conventional radiographs appeared normal, an increased alpha angle was present anterosuperiorly. Without the use of radial slices in MRA, the aSphericity would be underestimated in these patients.
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comparison of six radiographic projections to assess femoral head neck aSphericity
Clinical Orthopaedics and Related Research, 2006Co-Authors: Dominik C Meyer, Reinhold Ganz, Martin Beck, Thomas J Ellis, Michael LeunigAbstract:Early radiographic detection of femoroacetabular impingement might prevent initiation and progression of osteoarthritis. The structural abnormality in femoral-induced femoroacetabular impingement (cam type) is frequently aSphericity at the anterosuperior head/neck contour. To determine which of six radiographic projections (anteroposterior, Dunn, Dunn/45 degrees flexion, cross-table/15 degrees internal rotation, cross-table/neutral rotation, and cross-table/15 degrees external rotation) best identifies femoral head/neck aSphericity, we studied 21 desiccated femurs; 11 with an aspherical femoral head/neck contour and 10 with a spherical femoral head/neck contour. To radiographically quantify femoral head aSphericity, we measured the angle where the femoral head/neck leaves Sphericity (angle alpha). The aspherical femoral head/neck contours had a greater maximum angle alpha (70 degrees ) compared with the spherical head/neck contours (50 degrees ). The angle alpha varied depending on the radiographic projection: it was greatest in the Dunn view with 45 degrees hip flexion (71 degrees +/- 10 degrees ) and least in the cross-table view in 15 degrees external rotation (51 degrees +/- 7 degrees ). Diagnosis of a pathologic femoral head/neck contour depends on the radiologic projection. The Dunn view in 45 degrees or 90 degrees flexion or a cross-table projection in internal rotation best show femoral head/neck aSphericity, whereas anteroposterior or externally rotated cross-table views are likely to miss aSphericity. Level of Evidence: Prognostic study, level II-1 (retrospective study).
Thomas A Silvestrini - One of the best experts on this subject based on the ideXlab platform.
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characterization of the aspheric corneal surface with intrastromal corneal ring segments
Journal of Refractive Surgery, 1999Co-Authors: Debby K Holmeshiggin, Phillip C Baker, Terry E Burris, Thomas A SilvestriniAbstract:Purpose Anterior corneal surface aSphericity was examined in eyes of Phase II clinical trial participants, before and after intrastromal corneal ring segments (ICRS, Intacs) refractive surgery, and surveyed for relationship to clinical visual performance. Methods Aspheric test objects with surface aSphericity (Q) ranging from -0.01 Q to -1.44 Q and base radius of curvatures ranging from 7.5 mm to 9.0 mm were measured topographically using videokeratography. Radius of curvature aSphericity profile plots were produced for test objects and compared to similar plots created for trial participant eyes (n=25) to quantify corneal aSphericity. The potential effects of different amounts of corneal aSphericity were assessed using measurement of uncorrected and spectacle-corrected visual acuity and photopic contrast sensitivity. Results Preoperative corneal aSphericity ranged from -0.01 Q to -0.81 Q and postoperative from -0.01 Q to -1.44 Q. Preoperative uncorrected visual acuity was significantly related to corneal aSphericity; more myopic eyes tended to have more prolate corneal aSphericity. Corneal aSphericity was not significantly related to spectacle-corrected visual acuity or photopic contrast sensitivity, before or after surgery. Conclusion Postoperative corneal aSphericity values demonstrated that intrastromal corneal ring segments (Intacs) produced a prolate aspheric surface for myopic correction from -1.00 D to -6.00 D. This study indicated that the range of corneal aSphericity measured in these 25 eyes, before and after surgery, provided good visual acuity and normal contrast sensitivity.
Jose F Alfonso - One of the best experts on this subject based on the ideXlab platform.
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long term follow up of intrastromal corneal ring segments 210 degree arc length in central keratoconus with high corneal aSphericity
Cornea, 2017Co-Authors: Carlos Lisa, Fernandezvega L Cueto, Aranzazu Poolopez, David Madridcosta, Jose F AlfonsoAbstract:Purpose:To assess the long-term outcomes of implanting intrastromal corneal ring segments (ICRSs) to correct central keratoconus with a high corneal aSphericity value.Methods:Forty-three eyes with central keratoconus with a corneal aSphericity value ≥−1.00 were evaluated before and after implanting
