95,977 research outputs found
Visual and computational analysis of structure-activity relationships in high-throughput screening data
Novel analytic methods are required to assimilate the large volumes of structural and bioassay data generated by combinatorial chemistry and high-throughput screening programmes in the pharmaceutical and agrochemical industries. This paper reviews recent work in visualisation and data mining that can be used to develop structure-activity relationships from such chemical/biological datasets
Deep Metric Learning and Image Classification with Nearest Neighbour Gaussian Kernels
We present a Gaussian kernel loss function and training algorithm for
convolutional neural networks that can be directly applied to both distance
metric learning and image classification problems. Our method treats all
training features from a deep neural network as Gaussian kernel centres and
computes loss by summing the influence of a feature's nearby centres in the
feature embedding space. Our approach is made scalable by treating it as an
approximate nearest neighbour search problem. We show how to make end-to-end
learning feasible, resulting in a well formed embedding space, in which
semantically related instances are likely to be located near one another,
regardless of whether or not the network was trained on those classes. Our
approach outperforms state-of-the-art deep metric learning approaches on
embedding learning challenges, as well as conventional softmax classification
on several datasets.Comment: Accepted in the International Conference on Image Processing (ICIP)
2018. Formerly titled Nearest Neighbour Radial Basis Function Solvers for
Deep Neural Network
Hierarchical progressive surveys. Multi-resolution HEALPix data structures for astronomical images, catalogues, and 3-dimensional data cubes
Scientific exploitation of the ever increasing volumes of astronomical data
requires efficient and practical methods for data access, visualisation, and
analysis. Hierarchical sky tessellation techniques enable a multi-resolution
approach to organising data on angular scales from the full sky down to the
individual image pixels. Aims. We aim to show that the Hierarchical progressive
survey (HiPS) scheme for describing astronomical images, source catalogues, and
three-dimensional data cubes is a practical solution to managing large volumes
of heterogeneous data and that it enables a new level of scientific
interoperability across large collections of data of these different data
types. Methods. HiPS uses the HEALPix tessellation of the sphere to define a
hierarchical tile and pixel structure to describe and organise astronomical
data. HiPS is designed to conserve the scientific properties of the data
alongside both visualisation considerations and emphasis on the ease of
implementation. We describe the development of HiPS to manage a large number of
diverse image surveys, as well as the extension of hierarchical image systems
to cube and catalogue data. We demonstrate the interoperability of HiPS and
Multi-Order Coverage (MOC) maps and highlight the HiPS mechanism to provide
links to the original data. Results. Hierarchical progressive surveys have been
generated by various data centres and groups for ~200 data collections
including many wide area sky surveys, and archives of pointed observations.
These can be accessed and visualised in Aladin, Aladin Lite, and other
applications. HiPS provides a basis for further innovations in the use of
hierarchical data structures to facilitate the description and statistical
analysis of large astronomical data sets.Comment: 21 pages, 6 figures. Accepted for publication in Astronomy &
Astrophysic
Overview on spectral line source finding and visualisation
Here I will outline successes and challenges for finding spectral line
sources in large data cubes that are dominated by noise. This is a 3D challenge
as the sources we wish to catalog are spread over several spatial pixels and
spectral channels. While 2D searches can be applied, e.g., channel by channel,
optimal searches take into account the 3-dimensional nature of the sources. In
this overview I will focus on HI 21-cm spectral line source detection in
extragalactic surveys, in particular HIPASS, the "HI Parkes All-Sky Survey" and
WALLABY, the "ASKAP HI All-Sky Survey". I use the original HIPASS data to
highlight the diversity of spectral signatures of galaxies and gaseous clouds,
both in emission and absorption. Among others, I report the discovery of a 680
km/s wide HI absorption trough in the megamaser galaxy NGC 5793. Issues such as
source confusion and baseline ripples, typically encountered in single-dish HI
surveys, are much reduced in interferometric HI surveys. Several large HI
emission and absorption surveys are planned for the Australian Square Kilometre
Array Pathfinder (ASKAP): here we focus on WALLABY, the 21-cm survey of the sky
(Dec < +30 degr; z < 0.26) which will take about one year of observing time
with ASKAP. Novel phased array feeds ("radio cameras") will provide 30 square
degrees instantaneous field-of-view. WALLABY is expected to detect more than
500 000 galaxies, unveil their large-scale structures and cosmological
parameters, detect their extended, low-surface brightness disks as well as gas
streams and filaments between galaxies. It is a precursor for future HI surveys
with SKA Phase I and II, exploring galaxy formation and evolution. The
compilation of highly reliable and complete source catalogs will require
sophisticated source-finding algorithms as well as accurate source
parametrisation.Comment: 14 pages, 6 figures, PASA Special Issue on "Source Finding &
Visualisation", submitte
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