196,090 research outputs found
Local transformations of units in scalar-tensor cosmology
No full textThe physical equivalence of Einstein and Jordan frames in scalar-tensor theories was explained by Dicke in 1962: they are related by a local transformation of units. We discuss this point in a cosmological framework. Our main result is the construction of a formalism in which all the physical observables are frame-invariant. The application of this approach to CMB codes is at present under analysis. © 2007 IOP Publishing Ltd
Dynamical relaxation of the dark matter to baryon ratio
No full textA scalar field interacting differently with dark matter and baryons may explain why their ratio is of order unity today. We provide three working examples, checking them against the observations of Cosmic Microwave Background, (CMB), Large Scale Structure, supernovae Ia, and post-Newtonian tests of gravity. Such a scenario could make life much easier for supersymmetric dark matter candidates. © 2004 The American Physical Society
''Compost verde e fanghi da reflui urbani nella produzione di piante ornamentali in vaso''
No full textFully automated contour detection of the ascending aorta in cardiac 2D phase-contrast MRI
No full textPurpose In this study we proposed a fully automated method for localizing and segmenting the ascending aortic lumen with phase-contrast magnetic resonance imaging (PC-MRI). Material and methods Twenty-five phase-contrast series were randomly selected out of a large population dataset of patients whose cardiac MRI examination, performed from September 2008 to October 2013, was unremarkable. The local Ethical Committee approved this retrospective study. The ascending aorta was automatically identified on each phase of the cardiac cycle using a priori knowledge of aortic geometry. The frame that maximized the area, eccentricity, and solidity parameters was chosen for unsupervised initialization. Aortic segmentation was performed on each frame using active contouring without edges techniques. The entire algorithm was developed using Matlab R2016b. To validate the proposed method, the manual segmentation performed by a highly experienced operator was used. Dice similarity coefficient, Bland-Altman analysis, and Pearson's correlation coefficient were used as performance metrics. Results Comparing automated and manual segmentation of the aortic lumen on 714 images, Bland-Altman analysis showed a bias of â 6.68 mm2, a coefficient of repeatability of 91.22 mm2, a mean area measurement of 581.40 mm2, and a reproducibility of 85%. Automated and manual segmentation were highly correlated (R = 0.98). The Dice similarity coefficient versus the manual reference standard was 94.6 ± 2.1% (mean ± standard deviation). Conclusion A fully automated and robust method for identification and segmentation of ascending aorta on PC-MRI was developed. Its application on patients with a variety of pathologic conditions is advisable
GENETIC VARIABILITY AND TAXONOMICAL CONSIDERATIONS ABOUT SIX SPECIES OF EUROPEAN CARDUELINE FINCHES (AVES, PASSERIFORMES).
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Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
A Consistent High‐Resolution Catalog of Induced Seismicity in Basel Based on Matched Filter Detection and Tailored Post‐Processing
No full textSeismic monitoring of the Basel Enhanced Geothermal System has been running for more than a decade. Yet the details of the long-term behavior of its induced seismicity remained unexplored because a seismic event catalog with consistent detection sensitivity and magnitudes did not exist. This knowledge is essential for developing guidelines and mitigation procedures on how to safely operate and terminate injection activities. Only few observational data exist that cover all phases of such projects in a consistent manner. Here we describe a method that overcomes these deficiencies based on sensitive matched filter detection and a machine learning approach to remove false detections. With an emphasis on consistency, we create a catalog that contains more than 280,000 events down to M-w-1.5. The much higher temporal resolution allows us to analyze induced microearthquakes in great detail and to gain new insights. We resolved temporal variations of seismicity parameters and, in the post-operational phase, a preferential temporal clustering of events. We find a breakdown in the Gutenberg-Richter scaling during reservoir stimulation, which may have physical reasons or could be caused by a method-independent detection limit during high event rates. The scaling breakdown has implications for the design of Adaptive Traffic Light Systems and may limit the potential of real-time mitigation strategies in future Enhanced Geothermal System projects. Nevertheless, our catalog gives the opportunity to study the temporal evolution of the sequence in unprecedented detail, which will help to better understand the physical processes in a geothermal reservoir, potentially not only in the Basel case
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