314 research outputs found
A Combined Deep Learning-Gradient Boosting Machine Framework for Fluid Intelligence Prediction
The ABCD Neurocognitive Prediction Challenge is a community driven
competition asking competitors to develop algorithms to predict fluid
intelligence score from T1-w MRIs. In this work, we propose a deep learning
combined with gradient boosting machine framework to solve this task. We train
a convolutional neural network to compress the high dimensional MRI data and
learn meaningful image features by predicting the 123 continuous-valued derived
data provided with each MRI. These extracted features are then used to train a
gradient boosting machine that predicts the residualized fluid intelligence
score. Our approach achieved mean square error (MSE) scores of 18.4374,
68.7868, and 96.1806 for the training, validation, and test set respectively.Comment: Challenge in Adolescent Brain Cognitive Development Neurocognitive
Predictio
Partial Volume Segmentation of Brain MRI Scans of any Resolution and Contrast
Partial voluming (PV) is arguably the last crucial unsolved problem in
Bayesian segmentation of brain MRI with probabilistic atlases. PV occurs when
voxels contain multiple tissue classes, giving rise to image intensities that
may not be representative of any one of the underlying classes. PV is
particularly problematic for segmentation when there is a large resolution gap
between the atlas and the test scan, e.g., when segmenting clinical scans with
thick slices, or when using a high-resolution atlas. In this work, we present
PV-SynthSeg, a convolutional neural network (CNN) that tackles this problem by
directly learning a mapping between (possibly multi-modal) low resolution (LR)
scans and underlying high resolution (HR) segmentations. PV-SynthSeg simulates
LR images from HR label maps with a generative model of PV, and can be trained
to segment scans of any desired target contrast and resolution, even for
previously unseen modalities where neither images nor segmentations are
available at training. PV-SynthSeg does not require any preprocessing, and runs
in seconds. We demonstrate the accuracy and flexibility of the method with
extensive experiments on three datasets and 2,680 scans. The code is available
at https://github.com/BBillot/SynthSeg.Comment: accepted for MICCAI 202
Determination of composition and structure of spongy bone tissue in human head of femur by Raman spectral mapping
Biomechanical properties of bone depend on the composition and organization of collagen fibers. In this study, Raman microspectroscopy was employed to determine the content of mineral and organic constituents and orientation of collagen fibers in spongy bone in the human head of femur at the microstructural level. Changes in composition and structure of trabecula were illustrated using Raman spectral mapping. The polarized Raman spectra permit separate analysis of local variations in orientation and composition. The ratios of Îœ2PO43â/Amide III, Îœ4PO43â/Amide III and Îœ1CO32â/Îœ2PO43â are used to describe relative amounts of spongy bone components. The Îœ1PO43â/Amide I ratio is quite susceptible to orientation effect and brings information on collagen fibers orientation. The results presented illustrate the versatility of the Raman method in the study of bone tissue. The study permits better understanding of bone physiology and evaluation of the biomechanical properties of bone
Mechanical model for a collagen fibril pair in extracellular matrix
In this paper, we model the mechanics of a collagen pair in the connective
tissue extracellular matrix that exists in abundance throughout animals,
including the human body. This connective tissue comprises repeated units of
two main structures, namely collagens as well as axial, parallel and regular
anionic glycosaminoglycan between collagens. The collagen fibril can be modeled
by Hooke's law whereas anionic glycosaminoglycan behaves more like a
rubber-band rod and as such can be better modeled by the worm-like chain model.
While both computer simulations and continuum mechanics models have been
investigated the behavior of this connective tissue typically, authors either
assume a simple form of the molecular potential energy or entirely ignore the
microscopic structure of the connective tissue. Here, we apply basic physical
methodologies and simple applied mathematical modeling techniques to describe
the collagen pair quantitatively. We find that the growth of fibrils is
intimately related to the maximum length of the anionic glycosaminoglycan and
the relative displacement of two adjacent fibrils, which in return is closely
related to the effectiveness of anionic glycosaminoglycan in transmitting
forces between fibrils. These reveal the importance of the anionic
glycosaminoglycan in maintaining the structural shape of the connective tissue
extracellular matrix and eventually the shape modulus of human tissues. We also
find that some macroscopic properties, like the maximum molecular energy and
the breaking fraction of the collagen, are also related to the microscopic
characteristics of the anionic glycosaminoglycan
Gastrointestinal stromal tumour of the duodenum in childhood: a rare case report
<p>Abstract</p> <p>Background</p> <p>Gastrointestinal stromal tumours (GISTs) are uncommon primary mesenchymal tumours of the gastrointestinal tract mostly observed in the adults. Duodenal GISTs are relatively rare in adults and it should be regarded as exceptional in childhood. In young patients duodenal GISTs may be a source of potentially lethal haemorrhage and this adds diagnostic and therapeutic dilemmas to the concern about the long-term outcome.</p> <p>Case presentation</p> <p>A 14-year-old boy was referred to our hospital with severe anaemia due to recurrent episodes of upper gastrointestinal haemorrhage. Endoscopy, small bowel series, scintigraphy and video capsule endoscopy previously done elsewhere were negative. Shortly after the admission, the patient underwent emergency surgery for severe recurrence of the bleeding. At surgery, a 4 cm solid mass arising from the wall of the fourth portion of the duodenum was identified. The invasion and the erosion of the duodenal mucosa was confirmed by intra-operative pushed duodenoscopy. The mass was resected by a full-thickness duodenal wall excision with adequate grossly free margins. Immunohistochemical analysis of the specimen revealed to be positive for CD117 (c-KIT protein) consistent with a diagnosis of GIST. The number of mitoses was < 5/50 HPF. Mutational analysis for c-KIT/PDGFRA tyrosine kinase receptor genes resulted in a wildtype pattern. The patient had an uneventful course and he has remained disease-free during two years of follow-up.</p> <p>Conclusion</p> <p>Duodenal GISTs in children are very rare and may present with massive bleeding. Cure can be achieved by complete surgical resection, but even in the low-aggressive tumours the long-term outcome may be unpredictable.</p
Self-consistent Spectral Function for Non-Degenerate Coulomb Systems and Analytic Scaling Behaviour
Novel results for the self-consistent single-particle spectral function and
self-energy are presented for non-degenerate one-component Coulomb systems at
various densities and temperatures. The GW^0-method for the dynamical
self-energy is used to include many-particle correlations beyond the
quasi-particle approximation. The self-energy is analysed over a broad range of
densities and temperatures (n=10^17/cm^3-10^27/cm^3, T=10^2 eV/k_B-10^4
eV/k_B). The spectral function shows a systematic behaviour, which is
determined by collective plasma modes at small wavenumbers and converges
towards a quasi-particle resonance at higher wavenumbers. In the low density
limit, the numerical results comply with an analytic scaling law that is
presented for the first time. It predicts a power-law behaviour of the
imaginary part of the self-energy, Im Sigma ~ -n^(1/4). This resolves a long
time problem of the quasi-particle approximation which yields a finite
self-energy at vanishing density.Comment: 28 pages, 9 figure
A novel underuse model shows that inactivity but not ovariectomy determines the deteriorated material properties and geometry of cortical bone in the tibia of adult rats
Our goal in this study was to determine to what extent the physiologic consequences of ovariectomy (OVX) in bones are exacerbated by a lack of daily activity such as walking. We forced 14-week-old female rats to be inactive for 15Â weeks with a unique experimental system that prevents standing and walking while allowing other movements. Tibiae, femora, and 4th lumbar vertebrae were analyzed by peripheral quantitative computed tomography (pQCT), microfocused X-ray computed tomography (micro-CT), histology, histomorphometry, Raman spectroscopy, and the three-point bending test. Contrary to our expectation, the exacerbation was very much limited to the cancellous bone parameters. Parameters of femur and tibia cortical bone were affected by the forced inactivity but not by OVX: (1) cross-sectional moment of inertia was significantly smaller in Sham-Inactive rat bones than that of their walking counterparts; (2) the number of sclerostin-positive osteocytes per unit cross-sectional area was larger in Sham-Inactive rat bones than in Sham-Walking rat bones; and (3) material properties such as ultimate stress of inactive rat tibia was lower than that of their walking counterparts. Of note, the additive effect of inactivity and OVX was seen only in a few parameters, such as the cancellous bone mineral density of the lumbar vertebrae and the structural parameters of cancellous bone in the lumbar vertebrae/tibiae. It is concluded that the lack of daily activity is detrimental to the strength and quality of cortical bone in the femur and tibia of rats, while lack of estrogen is not. Our inactive rat model, with the older rats, will aid the study of postmenopausal osteoporosis, the etiology of which may be both hormonal and mechanical
Leading-order QCD Analysis of Neutrino-Induced Dimuon Events
The results of a leading-order QCD analysis of neutrino-induced charm production are presented. They are based on a sample of 4111 \numu- and 871 \anumu-induced opposite-sign dimuon events with , , observed in the CHARM~II detector exposed to the CERN wideband neutrino and antineutrino beams. The analysis yields the value of \linebreak the charm quark mass and the Cabibbo--Kobayashi--Maskawa matrix element . The strange quark content of the nucleon is found to be suppressed with respect to non-strange sea quarks by a factor
Experimental search for muonic photons
We report new limits on the production of muonic photons in the CERN neutrino beam. The results are based on the analysis of neutrino production of dimuons in the CHARM II detector. A CL limit on the coupling constant of muonic photons, is derived for a muon neutrino mass in the range eV. This improves the limit obtained from a precision measurement of the anomalous magnetic moment of the muon by a factor from 8 to 4
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