367 research outputs found
Misdiagnosis of acute subarachnoid hemorrhage in the era of multimodal diagnostic options
No full textPatients suffering from aneurysmatic Subarachnoid Hemorrhage (SAH) may present with a variety of symptoms. The aim of this study is to evaluate the spectrum of misdiagnoses and to analyze the significance of delay of correct diagnosis on the clinical outcome
Distortions of parton distributions due to multiquark effects
No full textIt has been observed that the momentum distributions of partons in bound nuclei are distorted relative to those of free protons and neutrons. This phenomenon was first observed in deep inelastic scattering experiments with muon and neutrino beams on nuclear targets and is known as the EMC effect. Similar phenomena have been observed in other high energy interactions such as the Drell-Yan process, the hadroproduction of direct photons, and the resonance production of charmonium and bottomonium states. In this work we investigate the possibility that these effects are predominantly of partonic origin. Standard nuclear quantum mechanics predicts that there is a non-zero probability for bound nucleons to overlap forming complex color singlets. We examine whether the observed EMC-type effects can be attributed to the difference between the parton momentum distributions in such clusters and those in single nucleons. We present a systematic way of determining these distributions in the Bjorken scaling limit and of estimating the average number of multiquark clusters in nuclei. The model predicts depletion of the valence quark and enhancement of the ocean quark and gluon components as the cluster baryon number increases. These properties can naturally explain significant features of the high energy behavior of nuclear targets.</p
Predictive anatomical factors for rupture in middle cerebral artery mirror bifurcation aneurysms
No full textOBJECTIVEThe aim of this study was to define predictive factors for rupture of middle cerebral artery (MCA) mirror bifurcation aneurysms.METHODSThe authors retrospectively analyzed the data in patients with ruptured MCA bifurcation aneurysms with simultaneous presence of an unruptured MCA bifurcation mirror aneurysm treated in two neurosurgical centers. The following parameters were measured and analyzed with the statistical software R: neck, dome, and width of both MCA aneurysms—including neck/dome and width/neck ratios, shape of the aneurysms (regular vs irregular), inflow angle of both MCA aneurysms, and the diameters of the bilateral A1 and M1 segments and the frontal and temporal M2 trunks, as well as the bilateral diameter of the internal carotid artery (ICA).RESULTSThe authors analyzed the data of 44 patients (15 male and 29 female, mean age 50.1 years). Starting from the usual significance level of 0.05, the Sidak-corrected significance level is 0.0039. The diameter of the measured vessels was statistically not significant, nor was the inflow angle. The size of the dome was highly significant (p = 0.0000069). The size of the neck (p = 0.0047940) and the width of the aneurysms (p = 0.0056902) were slightly nonsignificant at the stated significance level of 0.0039. The shape of the aneurysms was bilaterally identical in 22 cases (50%). In cases of asymmetrical presentation of the aneurysm shape, 19 (86.4%) ruptured aneurysms were irregular and 3 (13.6%) had a regular shape (p = 0.001).CONCLUSIONSIn this study the authors show that the extraaneurysmal flow dynamics in mirror aneurysms are nonsignificant, and the aneurysmal geometry also does not seem to play a role as a predictor for rupture. The only predictors for rupture were size and shape of the aneurysms. It seems as though under the same conditions, one of the two aneurysms suffers changes in its wall and starts growing in a more or less stochastic manner. Newer imaging methods should enable practitioners to see which aneurysm has an unstable wall, to predict the rupture risk. At the moment one can only conclude that in cases of MCA mirror aneurysms the larger one, with or without shape irregularities, is the unstable aneurysm and that this is the one that needs to be treated.</jats:sec
Predictive Modular Neural Networks
No full textThe subject of this book is predictive modular neural networks and their ap plication to time series problems: classification, prediction and identification. The intended audience is researchers and graduate students in the fields of neural networks, computer science, statistical pattern recognition, statistics, control theory and econometrics. Biologists, neurophysiologists and medical engineers may also find this book interesting. In the last decade the neural networks community has shown intense interest in both modular methods and time series problems. Similar interest has been expressed for many years in other fields as well, most notably in statistics, control theory, econometrics etc. There is a considerable overlap (not always recognized) of ideas and methods between these fields. Modular neural networks come by many other names, for instance multiple models, local models and mixtures of experts. The basic idea is to independently develop several "subnetworks" (modules), which may perform the same or re lated tasks, and then use an "appropriate" method for combining the outputs of the subnetworks. Some of the expected advantages of this approach (when compared with the use of "lumped" or "monolithic" networks) are: superior performance, reduced development time and greater flexibility. For instance, if a module is removed from the network and replaced by a new module (which may perform the same task more efficiently), it should not be necessary to retrain the aggregate networ
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