Atomic norm denoising with applications to line spectral estimation

Motivated by recent work on atomic norms in inverse problems, we propose a new approach to line spectral estimation that provides theoretical guarantees for the mean-squared-error (MSE) performance in the presence of noise and without knowledge of the model order. We propose an abstract theory of denoising with atomic norms and specialize this theory to provide a convex optimization problem for estimating the frequencies and phases of a mixture of complex exponentials. We show that the associated convex optimization problem can be solved in polynomial time via semidefinite programming (SDP). We also show that the SDP can be approximated by an l1-regularized least-squares problem that achieves nearly the same error rate as the SDP but can scale to much larger problems. We compare both SDP and l1-based approaches with classical line spectral analysis methods and demonstrate that the SDP outperforms the l1 optimization which outperforms MUSIC, Cadzow's, and Matrix Pencil approaches in terms of MSE over a wide range of signal-to-noise ratios.Comment: 27 pages, 10 figures. A preliminary version of this work appeared in the Proceedings of the 49th Annual Allerton Conference in September 2011. Numerous numerical experiments added to this version in accordance with suggestions by anonymous reviewer

The Ageing, Longevity and Crowding Out Effects on Private and Public Savings: Evidence from Dynamic Panel Analysis

Life-cycle theory predicts ageing exerting long-term macroeconomic impacts through the reduction of private savings. Ageing can be brought either through a fall in fertility rates or a rise in longevity. However, empirical research studying macroeconomic determinants of savings generally regard age dependency as the measure capturing the process of ageing, overlooking longevity exerting an opposite impact on private savings. Since longevity and dependency are correlated determinants of private savings, omitting either potentially causes omitted variable bias. This paper considers the joint effects age dependency and longevity have on savings. In contrast to the wider literature, not only private, but also public, savings was studied. Applying dynamic panel modelling techniques to a dataset of 55 countries from 1972-2004, age dependency is found to still exert a negative effect on private savings. However, it is found that some of these reductions can potentially be offset by increased longevity. The study also reveals some level of crowding out of private sector savings associated with changes in public sector savings and find that the Ricardian Equivalence Hypothesis cannot be entirely dismissed.

Improving classification accuracy of feedforward neural networks for spiking neuromorphic chips

Deep Neural Networks (DNN) achieve human level performance in many image analytics tasks but DNNs are mostly deployed to GPU platforms that consume a considerable amount of power. New hardware platforms using lower precision arithmetic achieve drastic reductions in power consumption. More recently, brain-inspired spiking neuromorphic chips have achieved even lower power consumption, on the order of milliwatts, while still offering real-time processing. However, for deploying DNNs to energy efficient neuromorphic chips the incompatibility between continuous neurons and synaptic weights of traditional DNNs, discrete spiking neurons and synapses of neuromorphic chips need to be overcome. Previous work has achieved this by training a network to learn continuous probabilities, before it is deployed to a neuromorphic architecture, such as IBM TrueNorth Neurosynaptic System, by random sampling these probabilities. The main contribution of this paper is a new learning algorithm that learns a TrueNorth configuration ready for deployment. We achieve this by training directly a binary hardware crossbar that accommodates the TrueNorth axon configuration constrains and we propose a different neuron model. Results of our approach trained on electroencephalogram (EEG) data show a significant improvement with previous work (76% vs 86% accuracy) while maintaining state of the art performance on the MNIST handwritten data set.Comment: IJCAI-2017. arXiv admin note: text overlap with arXiv:1605.0774

A long-lived spin-orbit-coupled degenerate dipolar Fermi gas

We describe the creation of a long-lived spin-orbit-coupled gas of quantum degenerate atoms using the most magnetic fermionic element, dysprosium. Spin-orbit-coupling arises from a synthetic gauge field created by the adiabatic following of degenerate dressed states comprised of optically coupled components of an atomic spin. Because of dysprosium's large electronic orbital angular momentum and large magnetic moment, the lifetime of the gas is limited not by spontaneous emission from the light-matter coupling, as for gases of alkali-metal atoms, but by dipolar relaxation of the spin. This relaxation is suppressed at large magnetic fields due to Fermi statistics. We observe lifetimes up to 400 ms, which exceeds that of spin-orbit-coupled fermionic alkali atoms by a factor of 10-100, and is close to the value obtained from a theoretical model. Elastic dipolar interactions are also observed to influence the Rabi evolution of the spin, revealing an interacting fermionic system. The long lifetime of this weakly interacting spin-orbit-coupled degenerate Fermi gas will facilitate the study of quantum many-body phenomena manifest at longer timescales, with exciting implications for the exploration of exotic topological quantum liquids.Comment: 11 pages, 8 figures, one appendi

Anisotropic collisions of dipolar Bose-Einstein condensates in the universal regime

We report the measurement of collisions between two Bose-Einstein condensates with strong dipolar interactions. The collision velocity is significantly larger than the internal velocity distribution widths of the individual condensates, and thus, with the condensates being sufficiently dilute, a halo corresponding to the two-body differential scattering cross section is observed. The results demonstrate a novel regime of quantum scattering, relevant to dipolar interactions, in which a large number of angular momentum states become coupled during the collision. We perform Monte-Carlo simulations to provide a detailed comparison between theoretical two-body cross sections and the experimental observations.Comment: 10 pages, 5 figure

Use of antivascular endothelial growth factor for diabetic macular edema

Rushmia Karim, Benjamin TangUniversity of Sydney School of Public Health, Concord Repatriation General Hospital, Concord, NSW, AustraliaBackground: Diabetic macular edema (DME) is one of the manifestations of diabetic retinopathy leading to loss of central vision and visual acuity. It manifests itself with swelling around the central part of the retina, the area responsible for sharp vision. Current treatment includes laser therapy and intravitreal steroids with preventative measures including diabetes control. No one treatment has guaranteed control of diabetic macular edema which leads to deteriorating visual acuity, function and quality of life in patients. Vascular endothelial growth factor (VEGF) has been shown to be a critical stimulus in the pathogenesis of macular edema secondary to diabetes.1 Antiangiogenic therapy encompassed treatment with anti-VEGF which inhibits VEGF-driven neovascularization hence macular edema leading to decreased visual acuity.Objective: For this review, we evaluated the effectiveness of intravitreal anti-VEGF in treating DME.Data sources: We identified five trials (n = 525) using electronic databases (Cochrane Central Register of Controlled Trials [Central], Medline®, and Excerpta Medica Database [EMBASE®]) in October 2008, supplemented by hand searching of reference lists, review articles, and conference abstracts.Methods: We included all randomized clinical trials (RCTs) evaluating any form of intravitreal anti-VEGF for treating DME. The main outcome factor was change in best-corrected visual acuity and central macular thickness. One author assessed eligibility, methodological quality, and extracted data. Meta analysis was performed when appropriate.Results: We included three trials of adequate methodological quality in our metaanalysis. Patients treated with anti-VEGF showed improvement in visual acuity of -0.17 (95% confidence interval [CI]: -0.23, -0.10) and central macular thickness -84.69 (95% CI: -117.09, -52.30). Patients treated with combined anti-VEGF and intravitreal triamcinolone showed improvement of visual acuity of -0.19 (95% CI: -0.27, -0.11) and central macular thickness mean change being –111.20 (95% CI: -148.13, -74.28).Conclusions: Anti-VEGF has been associated with an improvement in visual acuity and central macular thickness in the analysis, however trial analysis was of a short duration and further research is needed to determine long-term benefits.Keywords: anti-VEGF, diabetic macular edema, ranizubimab, Avastin®, pegaptani

Sugar additives for MALDI matrices improve signal allowing the smallest nucleotide change (A:T) in a DNA sequence to be resolved

Sample preparation for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) of DNA is critical for obtaining high quality mass spectra. Sample impurity, solvent content, substrate surface and environmental conditions (temperature and humidity) all affect the rate of matrix–analyte co-crystallization. As a result, laser fluence threshold for desorption/ionization varies from spot to spot. When using 3-hydroxypicolinic acid (3-HPA) as the matrix, laser fluence higher than the threshold value reduces mass resolution in time-of-flight (TOF) MS as the excess energy transferred to DNA causes metastable decay. This can be overcome by either searching for ‘hot’ spots or adjusting the laser fluence. However, both solutions may require a significant amount of operator manipulation and are not ideal for automatic measurements. We have added various sugars for crystallization with the matrix to minimize the transfer of excess laser energy to DNA molecules. Fructose and fucose were found to be the most effective matrix additives. Using these additives, mass resolution for DNA molecules does not show noticeable deterioration as laser energy increases. Improved sample preparation is important for the detection of single nucleotide polymorphisms (SNPs) using primer extension with a single nucleotide. During automatic data acquisition it is difficult to routinely detect heterozygous A/T mutations, which requires resolving a mass difference of 9 Da, unless a sugar is added during crystallization