976 research outputs found
Sparse approximation of multivariate functions from small datasets via weighted orthogonal matching pursuit
We show the potential of greedy recovery strategies for the sparse
approximation of multivariate functions from a small dataset of pointwise
evaluations by considering an extension of the orthogonal matching pursuit to
the setting of weighted sparsity. The proposed recovery strategy is based on a
formal derivation of the greedy index selection rule. Numerical experiments
show that the proposed weighted orthogonal matching pursuit algorithm is able
to reach accuracy levels similar to those of weighted minimization
programs while considerably improving the computational efficiency for small
values of the sparsity level
Decision and function problems based on boson sampling
Boson sampling is a mathematical problem that is strongly believed to be
intractable for classical computers, whereas passive linear interferometers can
produce samples efficiently. So far, the problem remains a computational
curiosity, and the possible usefulness of boson-sampling devices is mainly
limited to the proof of quantum supremacy. The purpose of this work is to
investigate whether boson sampling can be used as a resource of decision and
function problems that are computationally hard, and may thus have
cryptographic applications. After the definition of a rather general
theoretical framework for the design of such problems, we discuss their
solution by means of a brute-force numerical approach, as well as by means of
non-boson samplers. Moreover, we estimate the sample sizes required for their
solution by passive linear interferometers, and it is shown that they are
independent of the size of the Hilbert space.Comment: Close to the version published in PR
Effects of cigarette smoke extract on human airway smooth muscle cells in COPD
We hypothesised that the response to cigarette smoke in airway smooth muscle (ASM) cells from smokers with chronic obstructive pulmonary disease (COPD) would be intrinsically different from smokers without COPD, producing greater pro-inflammatory mediators and factors relating to airway remodelling. ASM cells were obtained from smokers with or without COPD, and then stimulated with cigarette smoke extract (CSE) or transforming growth factor-β1. The production of chemokines and matrix metalloproteinases (MMPs) were measured by ELISA, and the deposition of collagens by extracellular matrix ELISA. The effects of CSE on cell attachment and wound healing were measured by toluidine blue attachment and cell tracker green wound healing assays. CSE increased the release of CXCL8 and CXCL1 from human ASM cells, and cells from smokers with COPD produced more CSE-induced CXCL1. The production of MMP-1, -3 and -10, and the deposition of collagen VIII alpha 1 (COL8A1) were increased by CSE, especially in the COPD group which had higher production of MMP-1 and deposition of COL8A1. CSE decreased ASM cell attachment and wound healing in the COPD group only. ASM cells from smokers with COPD were more sensitive to CSE stimulation, which may explain, in part, why some smokers develop COPD. Copyright ©ERS 2014
Self-Control in Cyberspace: Applying Dual Systems Theory to a Review of Digital Self-Control Tools
Many people struggle to control their use of digital devices. However, our
understanding of the design mechanisms that support user self-control remains
limited. In this paper, we make two contributions to HCI research in this
space: first, we analyse 367 apps and browser extensions from the Google Play,
Chrome Web, and Apple App stores to identify common core design features and
intervention strategies afforded by current tools for digital self-control.
Second, we adapt and apply an integrative dual systems model of self-regulation
as a framework for organising and evaluating the design features found. Our
analysis aims to help the design of better tools in two ways: (i) by
identifying how, through a well-established model of self-regulation, current
tools overlap and differ in how they support self-control; and (ii) by using
the model to reveal underexplored cognitive mechanisms that could aid the
design of new tools.Comment: 11.5 pages (excl. references), 6 figures, 1 tabl
The set-down and set-up of directionally spread and crossing surface gravity wave groups
For sufficiently directionally spread surface gravity wave groups, the set-down of the wave-averaged free surface, first described by Longuet-Higgins and Stewart (J. Fluid Mech. vol. 13, 1962, pp. 481–504), can turn into a set-up. Using a multiple-scale expansion for two crossing wave groups, we examine the structure and magnitude of this wave-averaged set-up, which is part of a crossing wave pattern that behaves as a modulated partial standing wave: in space, it consists of a rapidly varying standing-wave pattern slowly modulated by the product of the envelopes of the two groups; in time, it grows and decays on the slow time scale associated with the translation of the groups. Whether this crossing wave pattern actually enhances the surface elevation at the point of focus depends on the phases of the linear wave groups, unlike the set-down, which is always negative and inherits the spatial structure of the underlying envelope(s). We present detailed laboratory measurements of the wave-averaged free surface, examining both single wave groups, varying the degree of spreading from small to very large, and the interaction between two wave groups, varying both the degree of spreading and the crossing angle between the groups. In both cases, we find good agreement between the experiments, our simple expressions for the set-down and set-up, and existing second-order theory based on the component-by-component interaction of individual waves with different frequencies and directions. We predict and observe a set-up for wave groups with a Gaussian angular amplitude distribution with standard deviations of above (for energy spectra), which is relatively large for realistic sea states, and for crossing sea states with angles of separation of and above, which are known to occur in the ocean
The Theory of the Interleaving Distance on Multidimensional Persistence Modules
In 2009, Chazal et al. introduced -interleavings of persistence
modules. -interleavings induce a pseudometric on (isomorphism
classes of) persistence modules, the interleaving distance. The definitions of
-interleavings and generalize readily to multidimensional
persistence modules. In this paper, we develop the theory of multidimensional
interleavings, with a view towards applications to topological data analysis.
We present four main results. First, we show that on 1-D persistence modules,
is equal to the bottleneck distance . This result, which first
appeared in an earlier preprint of this paper, has since appeared in several
other places, and is now known as the isometry theorem. Second, we present a
characterization of the -interleaving relation on multidimensional
persistence modules. This expresses transparently the sense in which two
-interleaved modules are algebraically similar. Third, using this
characterization, we show that when we define our persistence modules over a
prime field, satisfies a universality property. This universality result
is the central result of the paper. It says that satisfies a stability
property generalizing one which is known to satisfy, and that in
addition, if is any other pseudometric on multidimensional persistence
modules satisfying the same stability property, then . We also show
that a variant of this universality result holds for , over arbitrary
fields. Finally, we show that restricts to a metric on isomorphism
classes of finitely presented multidimensional persistence modules.Comment: Major revision; exposition improved throughout. To appear in
Foundations of Computational Mathematics. 36 page
Changes in targeted metabolomics in lung tissue of chronic obstructive pulmonary disease.
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a common chronic lung disease and its incidence is steadily increasing. COPD patients and mouse models of COPD share some similarities in lung pathology and physiology. We performed this study to explore the potential metabolic pathways involved in the pathogenesis of COPD and to discover the COPD-associated biomarkers. Furthermore, we aimed to examine how much the mouse model of COPD was similar and different to human COPD in terms of the altered metabolites and pathways. METHODS: Twenty human lung tissue samples (ten COPD and ten controls) and twelve mice lung tissue samples (six COPD and six controls) were analyzed by targeted HM350 metabolomics, and multivariate and pathway analysis were performed by Kyoto Encyclopedia of Genes and Genomes (KEGG) database. RESULTS: The counts of many metabolites such as amino acids, carbohydrates and carnitines were changed in both COPD patients and mice compared to controls, respectively. While lipid metabolism was changed only in COPD mice. After KEGG analysis, we found these altered metabolites involved in COPD through aging, apoptosis, oxidative stress and inflammation pathways. CONCLUSIONS: The expressions of metabolites changed in both COPD patients and cigarette smoke exposed (CS-exposed) mice. And there were also some differences between COPD patients and mouse models due to the differences between species. Our study suggested the dysregulation in amino acid metabolism, energy production pathway and perhaps lipid metabolism may be significantly related to the pathogenesis of COPD
On continuous variable quantum algorithms for oracle identification problems
We establish a framework for oracle identification problems in the continuous
variable setting, where the stated problem necessarily is the same as in the
discrete variable case, and continuous variables are manifested through a
continuous representation in an infinite-dimensional Hilbert space. We apply
this formalism to the Deutsch-Jozsa problem and show that, due to an
uncertainty relation between the continuous representation and its
Fourier-transform dual representation, the corresponding Deutsch-Jozsa
algorithm is probabilistic hence forbids an exponential speed-up, contrary to a
previous claim in the literature.Comment: RevTeX4, 15 pages with 10 figure
Translocations as Experiments in the Ecological Resilience of an Asocial Mega-Herbivore
Species translocations are remarkable experiments in evolutionary ecology, and increasingly critical to biodiversity conservation. Elaborate socio-ecological hypotheses for translocation success, based on theoretical fitness relationships, are untested and lead to complex uncertainty rather than parsimonious solutions. We used an extraordinary 89 reintroduction and 102 restocking events releasing 682 black rhinoceros (Diceros bicornis) to 81 reserves in southern Africa (1981–2005) to test the influence of interacting socio-ecological and individual characters on post-release survival. We predicted that the socio-ecological context should feature more prominently after restocking than reintroduction because released rhinoceros interact with resident conspecifics. Instead, an interaction between release cohort size and habitat quality explained reintroduction success but only individuals' ages explained restocking outcomes. Achieving translocation success for many species may not be as complicated as theory suggests. Black rhino, and similarly asocial generalist herbivores without substantial predators, are likely to be resilient to ecological challenges and robust candidates for crisis management in a changing world
Persistent topology for natural data analysis - A survey
Natural data offer a hard challenge to data analysis. One set of tools is
being developed by several teams to face this difficult task: Persistent
topology. After a brief introduction to this theory, some applications to the
analysis and classification of cells, lesions, music pieces, gait, oil and gas
reservoirs, cyclones, galaxies, bones, brain connections, languages,
handwritten and gestured letters are shown
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