100 research outputs found
3D Masked Autoencoders with Application to Anomaly Detection in Non-Contrast Enhanced Breast MRI
Self-supervised models allow (pre-)training on unlabeled data and therefore
have the potential to overcome the need for large annotated cohorts. One
leading self-supervised model is the masked autoencoder (MAE) which was
developed on natural imaging data. The MAE is masking out a high fraction of
visual transformer (ViT) input patches, to then recover the uncorrupted images
as a pretraining task. In this work, we extend MAE to perform anomaly detection
on breast magnetic resonance imaging (MRI). This new model, coined masked
autoencoder for medical imaging (MAEMI) is trained on two non-contrast enhanced
MRI sequences, aiming at lesion detection without the need for intravenous
injection of contrast media and temporal image acquisition. During training,
only non-cancerous images are presented to the model, with the purpose of
localizing anomalous tumor regions during test time. We use a public dataset
for model development. Performance of the architecture is evaluated in
reference to subtraction images created from dynamic contrast enhanced
(DCE)-MRI
Influence of Substrate Temperature on Structural and Morphological Properties of SnO2 Nanostructured Thin Films
SnO2 nanostructures thin films with thickness of 500 nm were prepared by electron beam-physical vapor deposition on glass substrate at temperature of 300, 373, 443, and 583 K. Structural and morphological properties of these nanostructured thin films were studied by Scanning and Transmission Electron Microscopy (SEM, TEM) and Atomic Force Microscope (AFM) methods. The changes in structural and morphological properties are found at different temperatures. Increase temperature causes important change of the structural and morphological properties. The sample prepared at 300 K has crystalline structure and the sample prepared at 583 K has amorphous structure. Roughness parameters have low values at 300, 373, 443 K as opposed to the values obtained at 583 K. This different behavior may be due to the amorphous structure of the sample that was observed in the TEM analysis
Equilibrium swelling and universal ratios in dilute polymer solutions: Exact Brownian dynamics simulations for a delta function excluded volume potential
A narrow Gaussian excluded volume potential, which tends to a delta-function
repulsive potential in the limit of a width parameter d* going to zero, has
been used to examine the universal consequences of excluded volume interactions
on the equilibrium and linear viscoelastic properties of dilute polymer
solutions. Brownian dynamics simulations data, acquired for chains of finite
length, has been extrapolated to the limit of infinite chain length to obtain
model independent predictions. The success of the method in predicting well
known aspects of static solution properties suggests that it can be used as a
systematic means by which the influence of solvent quality on both equilibrium
and non-equilibrium properties can be studied.Comment: Revised version submitted to Physical Review Letters. 4 pages, 2
figures (revised with additional data
Recent experimental probes of shear banding
Recent experimental techniques used to investigate shear banding are
reviewed. After recalling the rheological signature of shear-banded flows, we
summarize the various tools for measuring locally the microstructure and the
velocity field under shear. Local velocity measurements using dynamic light
scattering and ultrasound are emphasized. A few results are extracted from
current works to illustrate open questions and directions for future research.Comment: Review paper, 23 pages, 11 figures, 204 reference
- …