Recurrent Fully Convolutional Neural Networks for Multi-slice MRI Cardiac Segmentation

In cardiac magnetic resonance imaging, fully-automatic segmentation of the heart enables precise structural and functional measurements to be taken, e.g. from short-axis MR images of the left-ventricle. In this work we propose a recurrent fully-convolutional network (RFCN) that learns image representations from the full stack of 2D slices and has the ability to leverage inter-slice spatial dependences through internal memory units. RFCN combines anatomical detection and segmentation into a single architecture that is trained end-to-end thus significantly reducing computational time, simplifying the segmentation pipeline, and potentially enabling real-time applications. We report on an investigation of RFCN using two datasets, including the publicly available MICCAI 2009 Challenge dataset. Comparisons have been carried out between fully convolutional networks and deep restricted Boltzmann machines, including a recurrent version that leverages inter-slice spatial correlation. Our studies suggest that RFCN produces state-of-the-art results and can substantially improve the delineation of contours near the apex of the heart.Comment: MICCAI Workshop RAMBO 201

Serving performance in a suprapostural visual signal detection task: context-dependent and direction-specific control of body sway with fingertip light touch

Keeping gaze fixed on a target during visual smooth pursuit or touch light during fingertip contact while standing may resemble the goals of a suprapostural task with the implicit demands to minimize self-imposed sensorimotor variability. To test whether the principle of a suprapostural task generalizes to more complex sensorimotor stimulus-response mappings, we investigated how the control of body sway is influenced by an implicit feedback coupling (IFC) between the variability of touch forces at the contact point and perceptual difficulty, that is vertical jitter of a horizontally oscillating Landolt-C, in a visual signal detection task (VSDT). Mediolateral (ML) body sway of ten young healthy adults was assessed in four IFC conditions: (1) LT with independent jitter (LT-IJ), (2) LT with jitter depending on LT contact force (LT-CF), (3) LT with jitter depending on body sway (LT-BS), and (4) no contact with jitter depending on body sway (NT-BS). We assumed that the postural control system would be responsive to IFC and therefore reduce body sway in both IFC conditions. Resulting mediolateral body sway differed between the IFC conditions. Reduced sway was found in LT-CF and LT-BS compared to LT-IJ and in LT-BS compared to NT-BS. Our results demonstrate that processes controlling body sway can reduce postural variability below a variability level achieved by LT augmentation of body sway-related feedback alone. Both direct (LT-CF) and indirect (LT-BS) IFC involvement of fingertip contact minimized sway, which implies that no hierarchy existed for whole body sway or precision of fingertip contact (integration of both control processes) or that they can be reversed flexibly (one facilitating the other) if it serves the implicit goal of reduced perceptual noise and enhanced performance within the context of our suprapostural VSDT

Polynomial Interrupt Timed Automata

Interrupt Timed Automata (ITA) form a subclass of stopwatch automata where reachability and some variants of timed model checking are decidable even in presence of parameters. They are well suited to model and analyze real-time operating systems. Here we extend ITA with polynomial guards and updates, leading to the class of polynomial ITA (PolITA). We prove the decidability of the reachability and model checking of a timed version of CTL by an adaptation of the cylindrical decomposition method for the first-order theory of reals. Compared to previous approaches, our procedure handles parameters and clocks in a unified way. Moreover, we show that PolITA are incomparable with stopwatch automata. Finally additional features are introduced while preserving decidability

Baryon-Baryon Interactions

After a short survey of some topics of interest in the study of baryon-baryon scattering, the recent Nijmegen energy dependent partial wave analysis (PWA) of the nucleon-nucleon data is reviewed. In this PWA the energy range for both pp and np is now 0 < Tlab < 350 MeV and a chi^2_{d.o.f.}=1.08 was reached. The implications for the pion-nucleon coupling constants are discussed. Comments are made with respect to recent discussions around this coupling constant in the literature. In the second part, we briefly sketch the picture of the baryon in several, more or less QCD-based, quark-models that have been rather prominent in the literature. Inspired by these pictures we constructed a new soft-core model for the nucleon-nucleon interaction and present the first results of this model in a chi^2 -fit to the new multi-energy Nijmegen PWA. With this new model we succeeded in narrowing the gap between theory and experiment at low energies. For the energies Tlab = 25-320 MeV we reached a record low chi^2_{p.d.p.} = 1.16. We finish the paper with some conclusions and an outlook describing the extension of the new model to baryon-baryon scattering.Comment: 12 pages LaTeX and one postscript figure included. Invited talk presented at the XIVth European Conference of Few-Body Problems in Physics, Amsterdam, August 23-28, 199

Legacy radionuclides in cryoconite and proglacial sediment on Orwell Glacier, Signy Island, Antarctica

Cryoconite is a specific type of material found on the surface of glaciers and icesheets. Samples of cryoconite were collected from the Orwell Glacier and its moraines, together with suspended sediment from the proglacial stream on Signy Island, part of the South Orkney Islands, Antarctica. The activity concentrations of certain fallout radionuclides were determined in the cryoconite, moraine and suspended sediment, in addition to particle size composition and %C and %N. For cryoconite samples (n = 5), mean activity concentrations (±1SD) of 137Cs, 210Pbun and 241Am were 13.2 ± 20.9, 66.1 ± 94.0 and 0.32 ± 0.64 Bq kg−1, respectively. Equivalent values for the moraine samples (n = 7) were 2.56 ± 2.75, 14.78 ± 12.44 and <1.0 Bq kg−1, respectively. For the composite suspended sediment sample, collected over 3 weeks in the ablation season, the values (± counting uncertainty) for 137Cs, 210Pbun and 241Am were 2.64 ± 0.88, 49.2 ± 11.9 and <1.0 Bq kg−1, respectively. Thus, fallout radionuclide activity concentrations were elevated in cryoconite relative to moraine and suspended sediment. In the case of 40K, the highest value was for the suspended sediment (1423 ± 166 Bq kg−1). The fallout radionuclides in cryoconite were 1–2 orders of magnitude greater than values in soils collected from other locations in Antarctica. This work further demonstrates that cryoconite likely scavenges fallout radionuclides (dissolved and particulate) in glacial meltwater. In the case of 40K, the greater value in suspended sediment implies a subglacial source. These results are amongst the relatively few that demonstrate the presence of fallout radionuclides in cryoconites at remote locations in the Southern Hemisphere. This work adds to the growing contention that elevated activities of fallout radionuclides, and other contaminants, in cryoconites are a global phenomenon and may be a risk to downstream terrestrial and aquatic ecosystems

Application of boundary detection information in breast tomosynthesis reconstruction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135006/1/mp1968.pd

Using item response theory to explore the psychometric properties of extended matching questions examination in undergraduate medical education

BACKGROUND: As assessment has been shown to direct learning, it is critical that the examinations developed to test clinical competence in medical undergraduates are valid and reliable. The use of extended matching questions (EMQ) has been advocated to overcome some of the criticisms of using multiple-choice questions to test factual and applied knowledge. METHODS: We analysed the results from the Extended Matching Questions Examination taken by 4th year undergraduate medical students in the academic year 2001 to 2002. Rasch analysis was used to examine whether the set of questions used in the examination mapped on to a unidimensional scale, the degree of difficulty of questions within and between the various medical and surgical specialties and the pattern of responses within individual questions to assess the impact of the distractor options. RESULTS: Analysis of a subset of items and of the full examination demonstrated internal construct validity and the absence of bias on the majority of questions. Three main patterns of response selection were identified. CONCLUSION: Modern psychometric methods based upon the work of Rasch provide a useful approach to the calibration and analysis of EMQ undergraduate medical assessments. The approach allows for a formal test of the unidimensionality of the questions and thus the validity of the summed score. Given the metric calibration which follows fit to the model, it also allows for the establishment of items banks to facilitate continuity and equity in exam standards

Isotropy of the velocity of light and the Sagnac effect

In this paper, it is shown, using a geometrical approach, the isotropy of the velocity of light measured in a rotating frame in Minkowski space-time, and it is verified that this result is compatible with the Sagnac effect. Furthermore, we find that this problem can be reduced to the solution of geodesic triangles in a Minkowskian cylinder. A relationship between the problems established on the cylinder and on the Minkowskian plane is obtained through a local isometry.Comment: LaTeX, 13 pages, 3 eps figures; typos corrected, added references, minor changes; to appear in "Relativity in Rotating Frames", ed. G. Rizzi G. and M.L. Ruggiero, Kluwer Academic Publishers, Dordrecht (2003

Legacy radionuclides in cryoconite and proglacial sediment on Orwell Glacier, Signy Island, Antarctica

Cryoconite is a specific type of material found on the surface of glaciers and icesheets. Samples of cryoconite were collected from the Orwell Glacier and its moraines, together with suspended sediment from the proglacial stream on Signy Island, part of the South Orkney Islands, Antarctica. The activity concentrations of certain fallout radionuclides were determined in the cryoconite, moraine and suspended sediment, in addition to particle size composition and %C and %N. For cryoconite samples (n = 5), mean activity concentrations (±1SD) of 137Cs, 210Pbun and 241Am were 13.2 ± 20.9, 66.1 ± 94.0 and 0.32 ± 0.64 Bq kg−1, respectively. Equivalent values for the moraine samples (n = 7) were 2.56 ± 2.75, 14.78 ± 12.44 and <1.0 Bq kg−1, respectively. For the composite suspended sediment sample, collected over 3 weeks in the ablation season, the values (± counting uncertainty) for 137Cs, 210Pbun and 241Am were 2.64 ± 0.88, 49.2 ± 11.9 and <1.0 Bq kg−1, respectively. Thus, fallout radionuclide activity concentrations were elevated in cryoconite relative to moraine and suspended sediment. In the case of 40K, the highest value was for the suspended sediment (1423 ± 166 Bq kg−1). The fallout radionuclides in cryoconite were 1–2 orders of magnitude greater than values in soils collected from other locations in Antarctica. This work further demonstrates that cryoconite likely scavenges fallout radionuclides (dissolved and particulate) in glacial meltwater. In the case of 40K, the greater value in suspended sediment implies a subglacial source. These results are amongst the relatively few that demonstrate the presence of fallout radionuclides in cryoconites at remote locations in the Southern Hemisphere. This work adds to the growing contention that elevated activities of fallout radionuclides, and other contaminants, in cryoconites are a global phenomenon and may be a risk to downstream terrestrial and aquatic ecosystems