Explicit and almost sure conditions for K/2 degrees of freedom

It is well known that in K-user constant single-antenna interference channels K/2 degrees of freedom (DoF) can be achieved for almost all channel matrices. Explicit conditions on the channel matrix to admit K/2 DoF are, however, not available. The purpose of this paper is to identify such explicit conditions, which are satisfied for almost all channel matrices. We also provide a construction of corresponding asymptotically DoF-optimal input distributions. The main technical tool used is a recent breakthrough result by Hochman in fractal geometry.Comment: To be presented at IEEE Int. Symp. Inf. Theory 2014, Honolulu, H

Super-Resolution from Short-Time Fourier Transform Measurements

While spike trains are obviously not band-limited, the theory of super-resolution tells us that perfect recovery of unknown spike locations and weights from low-pass Fourier transform measurements is possible provided that the minimum spacing, $\Delta$, between spikes is not too small. Specifically, for a cutoff frequency of $f_c$, Donoho [2] shows that exact recovery is possible if $\Delta > 1/f_c$, but does not specify a corresponding recovery method. On the other hand, Cand\`es and Fernandez-Granda [3] provide a recovery method based on convex optimization, which provably succeeds as long as $\Delta > 2/f_c$. In practical applications one often has access to windowed Fourier transform measurements, i.e., short-time Fourier transform (STFT) measurements, only. In this paper, we develop a theory of super-resolution from STFT measurements, and we propose a method that provably succeeds in recovering spike trains from STFT measurements provided that $\Delta > 1/f_c$.Comment: IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), May 2014, to appea

Almost Lossless Analog Signal Separation

We propose an information-theoretic framework for analog signal separation. Specifically, we consider the problem of recovering two analog signals from a noiseless sum of linear measurements of the signals. Our framework is inspired by the groundbreaking work of Wu and Verd\'u (2010) on almost lossless analog compression. The main results of the present paper are a general achievability bound for the compression rate in the analog signal separation problem, an exact expression for the optimal compression rate in the case of signals that have mixed discrete-continuous distributions, and a new technique for showing that the intersection of generic subspaces with subsets of sufficiently small Minkowski dimension is empty. This technique can also be applied to obtain a simplified proof of a key result in Wu and Verd\'u (2010).Comment: To be presented at IEEE Int. Symp. Inf. Theory 2013, Istanbul, Turke

Anion-Sensitive Fluorophore Identifies the Drosophila Swell-Activated Chloride Channel in a Genome-Wide RNA Interference Screen

When cells swell in hypo-osmotic solutions, chloride-selective ion channels ($Cl_{swell}$) activate to reduce intracellular osmolality and prevent catastrophic cell rupture. Despite intensive efforts to assign a molecular identity to the mammalian $Cl_{swell}$ channel, it remains unknown. In an unbiased genome-wide RNA interference (RNAi) screen of Drosophila cells stably expressing an anion-sensitive fluorescent indicator, we identify Bestrophin 1 (dBest1) as the Drosophila $Cl_{swell}$ channel. Of the 23 screen hits with mammalian homologs and predicted transmembrane domains, only RNAi specifically targeting dBest1 eliminated the $Cl_{swell}$ current ($I_{Clswell}$). We further demonstrate the essential contribution of dBest1 to Drosophila $I_{Clswell}$ with the introduction of a human Bestrophin disease-associated mutation (W94C). Overexpression of the W94C construct in Drosophila cells significantly reduced the endogenous $I_{Clswell}$. We confirm that exogenous expression of dBest1 alone in human embryonic kidney (HEK293) cells creates a clearly identifiable Drosophila–like $I_{Clswell}$. In contrast, activation of mouse Bestrophin 2 (mBest2), the closest mammalian ortholog of dBest1, is swell-insensitive. The first 64 residues of dBest1 conferred swell activation to mBest2. The chimera, however, maintains mBest2-like pore properties, strongly indicating that the Bestrophin protein forms the $Cl_{swell}$ channel itself rather than functioning as an essential auxiliary subunit. dBest1 is an anion channel clearly responsive to swell; this activation depends upon its N-terminus

Control of arable crop pathogens; climate change mitigation, impacts and adaptation

© Springer Science+Business Media New York 2016. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1007/978-1-4939-3536-9_3In the context of threats to global food security from impacts of damaging crop diseases and of climate change, this chapter describes three aspects of the interactions between climate change and diseases that reduce arable crop yields. It considers the role of crop disease control in climate change mitigation, by estimating consequences for greenhouse gas (GHG) emissions of crop management strategies to control diseases, using UK oilseed rape and barley crops as examples. In this chapter we conclude that good control of crop diseases, resulting in more efficient use of nitrogen fertiliser, can decrease UK GHG from crop production by c. 1.6 Mt CO2 eq. each year. Within the chapter we discuss impacts of climate change on incidence of crop diseases and their effects on crop yields, using UK oilseed rape phoma stem canker and wheat fusarium ear blight as examples. For both these diseases, it is estimated that global warming will increase the range and severity of epidemics. To make such estimates, it is emphasised that it is important to estimate impacts of climate on both crop growth and disease development. In response to such projections of impacts of climate change, within this chapter we assess strategies for adaptation to climate change of crop disease management to decrease arable crop losses related to climate change, for both policymakers and farmers.Peer reviewe