677 research outputs found
Roto-Translation Equivariant Convolutional Networks: Application to Histopathology Image Analysis
Rotation-invariance is a desired property of machine-learning models for
medical image analysis and in particular for computational pathology
applications. We propose a framework to encode the geometric structure of the
special Euclidean motion group SE(2) in convolutional networks to yield
translation and rotation equivariance via the introduction of SE(2)-group
convolution layers. This structure enables models to learn feature
representations with a discretized orientation dimension that guarantees that
their outputs are invariant under a discrete set of rotations. Conventional
approaches for rotation invariance rely mostly on data augmentation, but this
does not guarantee the robustness of the output when the input is rotated. At
that, trained conventional CNNs may require test-time rotation augmentation to
reach their full capability. This study is focused on histopathology image
analysis applications for which it is desirable that the arbitrary global
orientation information of the imaged tissues is not captured by the machine
learning models. The proposed framework is evaluated on three different
histopathology image analysis tasks (mitosis detection, nuclei segmentation and
tumor classification). We present a comparative analysis for each problem and
show that consistent increase of performances can be achieved when using the
proposed framework
Attentive Group Equivariant Convolutional Networks
Although group convolutional networks are able to learn powerful
representations based on symmetry patterns, they lack explicit means to learn
meaningful relationships among them (e.g., relative positions and poses). In
this paper, we present attentive group equivariant convolutions, a
generalization of the group convolution, in which attention is applied during
the course of convolution to accentuate meaningful symmetry combinations and
suppress non-plausible, misleading ones. We indicate that prior work on visual
attention can be described as special cases of our proposed framework and show
empirically that our attentive group equivariant convolutional networks
consistently outperform conventional group convolutional networks on benchmark
image datasets. Simultaneously, we provide interpretability to the learned
concepts through the visualization of equivariant attention maps.Comment: Proceedings of the 37th International Conference on Machine Learning
(ICML), 202
Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation
The generation of tunable visible, infrared, and ultraviolet light is examined, along with the control of this light by means of novel mode-locking and modulation techniques. Transient mode-locking of the Nd:YAG laser and generation of short tunable pulses in the visible and the alkali metal inert gas excimer laser systems were investigated. Techniques for frequency conversion of high power and high energy laser radiation are discussed, along with high average power blue and UV laser light sources
Search for Rayleigh scattering in the atmosphere of GJ1214b
We investigate the atmosphere of GJ1214b, a transiting super-Earth planet
with a low mean density, by measuring its transit depth as a function of
wavelength in the blue optical portion of the spectrum. It is thought that this
planet is either a mini-Neptune, consisting of a rocky core with a thick,
hydrogen-rich atmosphere, or a planet with a composition dominated by water.
Most observations favor a water-dominated atmosphere with a small scale-height,
however, some observations indicate that GJ1214b could have an extended
atmosphere with a cloud layer muting the molecular features. In an atmosphere
with a large scale-height, Rayleigh scattering at blue wavelengths is likely to
cause a measurable increase in the apparent size of the planet towards the
blue. We observed the transit of GJ1214b in the B-band with the FOcal Reducing
Spectrograph (FORS) at the Very Large Telescope (VLT) and in the g-band with
both ACAM on the William Hershel Telescope (WHT) and the Wide Field Camera
(WFC) at the Isaac Newton Telescope (INT). We find a planet-to-star radius
ratio in the B-band of 0.1162+/-0.0017, and in the g-band 0.1180+/-0.0009 and
0.1174+/-0.0017 for the WHT & INT observations respectively. These optical data
do not show significant deviations from previous measurements at longer
wavelengths. In fact, a flat transmission spectrum across all wavelengths best
describes the combined observations. When atmospheric models are considered a
small scale-height water-dominated model fits the data best.Comment: Accepted for publication in Ap
Social determinants of content selection in the age of (mis)information
Despite the enthusiastic rhetoric about the so called \emph{collective
intelligence}, conspiracy theories -- e.g. global warming induced by chemtrails
or the link between vaccines and autism -- find on the Web a natural medium for
their dissemination. Users preferentially consume information according to
their system of beliefs and the strife within users of opposite narratives may
result in heated debates. In this work we provide a genuine example of
information consumption from a sample of 1.2 million of Facebook Italian users.
We show by means of a thorough quantitative analysis that information
supporting different worldviews -- i.e. scientific and conspiracist news -- are
consumed in a comparable way by their respective users. Moreover, we measure
the effect of the exposure to 4709 evidently false information (satirical
version of conspiracy theses) and to 4502 debunking memes (information aiming
at contrasting unsubstantiated rumors) of the most polarized users of
conspiracy claims. We find that either contrasting or teasing consumers of
conspiracy narratives increases their probability to interact again with
unsubstantiated rumors.Comment: misinformation, collective narratives, crowd dynamics, information
spreadin
The prevalence of microvascular obstruction in acute myocardial infarction: importance of ST elevation, infarct size, transmurality and infarct age
Clinical implications of microvascular obstruction and intramyocardial haemorrhage in acute myocardial infarction using cardiovascular magnetic resonance imaging
OBJECTIVES: To investigate the clinical implications of microvascular obstruction (MVO) and intramyocardial haemorrhage (IMH) in acute myocardial infarction (AMI). METHODS: Ninety patients with a first AMI undergoing primary percutaneous coronary intervention (PCI) were studied. T2-weighted, cine and late gadolinium-enhanced cardiovascular magnetic resonance imaging was performed at 5 ± 2 and 103 ± 11 days. Patients were categorised into three groups based on the presence or absence of MVO and IMH. RESULTS: MVO was observed in 54% and IMH in 43% of patients, and correlated significantly (r = 0.8, p < 0.001). Pre-PCI thrombolysis in myocardial infarction 3 flow was only observed in MVO(−)/IMH(−) patients. Infarct size and impairment of systolic function were largest in MVO(+)/IMH(+) patients (n = 39, 23 ± 9% and 47 ± 7%), smallest in MVO(−)/IMH(−) patients (n = 41, 8 ± 8% and 55 ± 8%) and intermediate in MVO(+)/IMH(−) patients (n = 10, 16 ± 7% and 51 ± 6%, p < 0.001). LVEF increased in all three subgroups at follow-up, but remained intermediate in MVO(+)/IMH(−) and was lowest in MVO(+)/IMH(+) patients. Using random intercept model analysis, only infarct size was an independent predictor for adverse LV remodelling. CONCLUSIONS: Intramyocardial haemorrhage and microvascular obstruction are strongly related. Pre-PCI TIMI 3 flow is less frequently observed in patients with MVO and IMH. Only infarct size was an independent predictor of LV remodelling
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