84 research outputs found
A Theoretical Analysis of Deep Neural Networks for Texture Classification
We investigate the use of Deep Neural Networks for the classification of
image datasets where texture features are important for generating
class-conditional discriminative representations. To this end, we first derive
the size of the feature space for some standard textural features extracted
from the input dataset and then use the theory of Vapnik-Chervonenkis dimension
to show that hand-crafted feature extraction creates low-dimensional
representations which help in reducing the overall excess error rate. As a
corollary to this analysis, we derive for the first time upper bounds on the VC
dimension of Convolutional Neural Network as well as Dropout and Dropconnect
networks and the relation between excess error rate of Dropout and Dropconnect
networks. The concept of intrinsic dimension is used to validate the intuition
that texture-based datasets are inherently higher dimensional as compared to
handwritten digits or other object recognition datasets and hence more
difficult to be shattered by neural networks. We then derive the mean distance
from the centroid to the nearest and farthest sampling points in an
n-dimensional manifold and show that the Relative Contrast of the sample data
vanishes as dimensionality of the underlying vector space tends to infinity.Comment: Accepted in International Joint Conference on Neural Networks, IJCNN
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Hematolological manifestations of COVID-19: From cytopenia to coagulopathy
This is an accepted manuscript of an article published by Wiley in European Journal of Haematology on 14/07/2020, available online: https://doi.org/10.1111/ejh.13491
The accepted version of the publication may differ from the final published version.Emerging data from the management of patients with Coronavirus Disease 2019 (COVID‐19) suggests multisystemic involvement, including the hemopoietic system. The hematological manifestations of COVID‐19 include blood count anomalies notably lymphopenia and neutrophilia which are of prognostic significance. Hyperferritinemia and elevated lactate dehydrogenase have also been associated with increased mortality. Furthermore, there is considerable evidence of a distinct coagulopathy associated with COVID‐19 characterised by elevated D‐dimers and an increased risk of thrombotic events. This comprehensive review summarises the latest evidence from published studies and discusses the implications of the various hematological manifestations of COVID‐19 with a view to guiding clinical management and risk stratification in this rapidly evolving pandemic.CA is a recipient of a clinical research fellowship funded by the CRUK-City of London Centre Clinical
Academic Training Programme Award [C355/A28852
Robust and Automatic Data Clustering: Dirichlet Process meets Median-of-Means
Clustering stands as one of the most prominent challenges within the realm of
unsupervised machine learning. Among the array of centroid-based clustering
algorithms, the classic -means algorithm, rooted in Lloyd's heuristic, takes
center stage as one of the extensively employed techniques in the literature.
Nonetheless, both -means and its variants grapple with noteworthy
limitations. These encompass a heavy reliance on initial cluster centroids,
susceptibility to converging into local minima of the objective function, and
sensitivity to outliers and noise in the data. When confronted with data
containing noisy or outlier-laden observations, the Median-of-Means (MoM)
estimator emerges as a stabilizing force for any centroid-based clustering
framework. On a different note, a prevalent constraint among existing
clustering methodologies resides in the prerequisite knowledge of the number of
clusters prior to analysis. Utilizing model-based methodologies, such as
Bayesian nonparametric models, offers the advantage of infinite mixture models,
thereby circumventing the need for such requirements. Motivated by these facts,
in this article, we present an efficient and automatic clustering technique by
integrating the principles of model-based and centroid-based methodologies that
mitigates the effect of noise on the quality of clustering while ensuring that
the number of clusters need not be specified in advance. Statistical guarantees
on the upper bound of clustering error, and rigorous assessment through
simulated and real datasets suggest the advantages of our proposed method over
existing state-of-the-art clustering algorithms
Deploying a Quantum Annealing Processor to Detect Tree Cover in Aerial Imagery of California
Quantum annealing is an experimental and potentially breakthrough computational technology for handling hard optimization problems, including problems of computer vision. We present a case study in training a production-scale classifier of tree cover in remote sensing imagery, using early-generation quantum annealing hardware built by D-wave Systems, Inc. Beginning within a known boosting framework, we train decision stumps on texture features and vegetation indices extracted from four-band, one-meter-resolution aerial imagery from the state of California. We then impose a regulated quadratic training objective to select an optimal voting subset from among these stumps. The votes of the subset define the classifier. For optimization, the logical variables in the objective function map to quantum bits in the hardware device, while quadratic couplings encode as the strength of physical interactions between the quantum bits. Hardware design limits the number of couplings between these basic physical entities to five or six. To account for this limitation in mapping large problems to the hardware architecture, we propose a truncation and rescaling of the training objective through a trainable metaparameter. The boosting process on our basic 108- and 508-variable problems, thus constituted, returns classifiers that incorporate a diverse range of color- and texture-based metrics and discriminate tree cover with accuracies as high as 92% in validation and 90% on a test scene encompassing the open space preserves and dense suburban build of Mill Valley, CA
A semi-analytical approach to perturbations in mutated hilltop inflation
We study cosmological perturbations and observational aspects for mutated
hilltop model of inflation. Employing mostly analytical treatment, we evaluate
observable parameters during inflation as well as post-inflationary
perturbations. This further leads to exploring observational aspects related to
Cosmic Microwave Background (CMB) radiation. This semi-analytical treatment
reduces complications related to numerical computation to some extent for
studying the different phenomena related to CMB angular power spectrum for
mutated hilltop inflation.Comment: 7 pages, 2 figures. Improved version to appear in IJMP
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Integration of silicon chip microstructures for in-line microbial cell lysis in soft microfluidics
The paper presents fabrication methodologies that integrate silicon components into soft microfluidic devices to perform microbial cell lysis for biological applications. The integration methodology consists of a silicon chip that is fabricated with microstructure arrays and embedded in a microfluidic device, which is driven by piezoelectric actuation to perform cell lysis by physically breaking microbial cell walls via micromechanical impaction. We present different silicon microarray geometries, their fabrication techniques, integration of said micropatterned silicon impactor chips into microfluidic devices, and device operation and testing on synthetic microbeads and two yeast species (S. cerevisiae and C. albicans) to evaluate their efficacy. The generalized strategy developed for integration of the micropatterned silicon impactor chip into soft microfluidic devices can serve as an important process step for a new class of hybrid silicon-polymeric devices for future cellular processing applications. The proposed integration methodology can be scalable and integrated as an in-line cell lysis tool with existing microfluidics assays
Neoplastic plasma cells generate an inflammatory environment within bone marrow and markedly alter the distribution of T cells between lymphoid compartments
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