@inproceedings{7116, abstract = {Training deep learning models has received tremendous research interest recently. In particular, there has been intensive research on reducing the communication cost of training when using multiple computational devices, through reducing the precision of the underlying data representation. Naturally, such methods induce system trade-offs—lowering communication precision could de-crease communication overheads and improve scalability; but, on the other hand, it can also reduce the accuracy of training. In this paper, we study this trade-off space, and ask:Can low-precision communication consistently improve the end-to-end performance of training modern neural networks, with no accuracy loss?From the performance point of view, the answer to this question may appear deceptively easy: compressing communication through low precision should help when the ratio between communication and computation is high. However, this answer is less straightforward when we try to generalize this principle across various neural network architectures (e.g., AlexNet vs. ResNet),number of GPUs (e.g., 2 vs. 8 GPUs), machine configurations(e.g., EC2 instances vs. NVIDIA DGX-1), communication primitives (e.g., MPI vs. NCCL), and even different GPU architectures(e.g., Kepler vs. Pascal). Currently, it is not clear how a realistic realization of all these factors maps to the speed up provided by low-precision communication. In this paper, we conduct an empirical study to answer this question and report the insights.}, author = {Grubic, Demjan and Tam, Leo and Alistarh, Dan-Adrian and Zhang, Ce}, booktitle = {Proceedings of the 21st International Conference on Extending Database Technology}, isbn = {9783893180783}, issn = {2367-2005}, location = {Vienna, Austria}, pages = {145--156}, publisher = {OpenProceedings}, title = {{Synchronous multi-GPU training for deep learning with low-precision communications: An empirical study}}, doi = {10.5441/002/EDBT.2018.14}, year = {2018}, } @inproceedings{7123, abstract = {Population protocols are a popular model of distributed computing, in which n agents with limited local state interact randomly, and cooperate to collectively compute global predicates. Inspired by recent developments in DNA programming, an extensive series of papers, across different communities, has examined the computability and complexity characteristics of this model. Majority, or consensus, is a central task in this model, in which agents need to collectively reach a decision as to which one of two states A or B had a higher initial count. Two metrics are important: the time that a protocol requires to stabilize to an output decision, and the state space size that each agent requires to do so. It is known that majority requires Ω(log log n) states per agent to allow for fast (poly-logarithmic time) stabilization, and that O(log2 n) states are sufficient. Thus, there is an exponential gap between the space upper and lower bounds for this problem. This paper addresses this question. On the negative side, we provide a new lower bound of Ω(log n) states for any protocol which stabilizes in O(n1–c) expected time, for any constant c > 0. This result is conditional on monotonicity and output assumptions, satisfied by all known protocols. Technically, it represents a departure from previous lower bounds, in that it does not rely on the existence of dense configurations. Instead, we introduce a new generalized surgery technique to prove the existence of incorrect executions for any algorithm which would contradict the lower bound. Subsequently, our lower bound also applies to general initial configurations, including ones with a leader. On the positive side, we give a new algorithm for majority which uses O(log n) states, and stabilizes in O(log2 n) expected time. Central to the algorithm is a new leaderless phase clock technique, which allows agents to synchronize in phases of Θ(n log n) consecutive interactions using O(log n) states per agent, exploiting a new connection between population protocols and power-of-two-choices load balancing mechanisms. We also employ our phase clock to build a leader election algorithm with a state space of size O(log n), which stabilizes in O(log2 n) expected time.}, author = {Alistarh, Dan-Adrian and Aspnes, James and Gelashvili, Rati}, booktitle = {Proceedings of the 29th Annual ACM-SIAM Symposium on Discrete Algorithms}, isbn = {9781611975031}, location = {New Orleans, LA, United States}, pages = {2221--2239}, publisher = {ACM}, title = {{Space-optimal majority in population protocols}}, doi = {10.1137/1.9781611975031.144}, year = {2018}, } @article{723, abstract = {Escaping local optima is one of the major obstacles to function optimisation. Using the metaphor of a fitness landscape, local optima correspond to hills separated by fitness valleys that have to be overcome. We define a class of fitness valleys of tunable difficulty by considering their length, representing the Hamming path between the two optima and their depth, the drop in fitness. For this function class we present a runtime comparison between stochastic search algorithms using different search strategies. The (1+1) EA is a simple and well-studied evolutionary algorithm that has to jump across the valley to a point of higher fitness because it does not accept worsening moves (elitism). In contrast, the Metropolis algorithm and the Strong Selection Weak Mutation (SSWM) algorithm, a famous process in population genetics, are both able to cross the fitness valley by accepting worsening moves. We show that the runtime of the (1+1) EA depends critically on the length of the valley while the runtimes of the non-elitist algorithms depend crucially on the depth of the valley. Moreover, we show that both SSWM and Metropolis can also efficiently optimise a rugged function consisting of consecutive valleys.}, author = {Oliveto, Pietro and Paixao, Tiago and Pérez Heredia, Jorge and Sudholt, Dirk and Trubenova, Barbora}, journal = {Algorithmica}, number = {5}, pages = {1604 -- 1633}, publisher = {Springer}, title = {{How to escape local optima in black box optimisation when non elitism outperforms elitism}}, doi = {10.1007/s00453-017-0369-2}, volume = {80}, year = {2018}, } @article{738, abstract = {This paper is devoted to automatic competitive analysis of real-time scheduling algorithms for firm-deadline tasksets, where only completed tasks con- tribute some utility to the system. Given such a taskset T , the competitive ratio of an on-line scheduling algorithm A for T is the worst-case utility ratio of A over the utility achieved by a clairvoyant algorithm. We leverage the theory of quantitative graph games to address the competitive analysis and competitive synthesis problems. For the competitive analysis case, given any taskset T and any finite-memory on- line scheduling algorithm A , we show that the competitive ratio of A in T can be computed in polynomial time in the size of the state space of A . Our approach is flexible as it also provides ways to model meaningful constraints on the released task sequences that determine the competitive ratio. We provide an experimental study of many well-known on-line scheduling algorithms, which demonstrates the feasibility of our competitive analysis approach that effectively replaces human ingenuity (required Preliminary versions of this paper have appeared in Chatterjee et al. ( 2013 , 2014 ). B Andreas Pavlogiannis pavlogiannis@ist.ac.at Krishnendu Chatterjee krish.chat@ist.ac.at Alexander Kößler koe@ecs.tuwien.ac.at Ulrich Schmid s@ecs.tuwien.ac.at 1 IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria 2 Embedded Computing Systems Group, Vienna University of Technology, Treitlstrasse 3, 1040 Vienna, Austria 123 Real-Time Syst for finding worst-case scenarios) by computing power. For the competitive synthesis case, we are just given a taskset T , and the goal is to automatically synthesize an opti- mal on-line scheduling algorithm A , i.e., one that guarantees the largest competitive ratio possible for T . We show how the competitive synthesis problem can be reduced to a two-player graph game with partial information, and establish that the compu- tational complexity of solving this game is Np -complete. The competitive synthesis problem is hence in Np in the size of the state space of the non-deterministic labeled transition system encoding the taskset. Overall, the proposed framework assists in the selection of suitable scheduling algorithms for a given taskset, which is in fact the most common situation in real-time systems design. }, author = {Chatterjee, Krishnendu and Pavlogiannis, Andreas and Kößler, Alexander and Schmid, Ulrich}, journal = {Real-Time Systems}, number = {1}, pages = {166 -- 207}, publisher = {Springer}, title = {{Automated competitive analysis of real time scheduling with graph games}}, doi = {10.1007/s11241-017-9293-4}, volume = {54}, year = {2018}, } @inproceedings{7407, abstract = {Proofs of space (PoS) [Dziembowski et al., CRYPTO'15] are proof systems where a prover can convince a verifier that he "wastes" disk space. PoS were introduced as a more ecological and economical replacement for proofs of work which are currently used to secure blockchains like Bitcoin. In this work we investigate extensions of PoS which allow the prover to embed useful data into the dedicated space, which later can be recovered. Our first contribution is a security proof for the original PoS from CRYPTO'15 in the random oracle model (the original proof only applied to a restricted class of adversaries which can store a subset of the data an honest prover would store). When this PoS is instantiated with recent constructions of maximally depth robust graphs, our proof implies basically optimal security. As a second contribution we show three different extensions of this PoS where useful data can be embedded into the space required by the prover. Our security proof for the PoS extends (non-trivially) to these constructions. We discuss how some of these variants can be used as proofs of catalytic space (PoCS), a notion we put forward in this work, and which basically is a PoS where most of the space required by the prover can be used to backup useful data. Finally we discuss how one of the extensions is a candidate construction for a proof of replication (PoR), a proof system recently suggested in the Filecoin whitepaper. }, author = {Pietrzak, Krzysztof Z}, booktitle = {10th Innovations in Theoretical Computer Science Conference}, isbn = {978-3-95977-095-8}, issn = {1868-8969}, location = {San Diego, CA, United States}, pages = {59:1--59:25}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik}, title = {{Proofs of catalytic space}}, doi = {10.4230/LIPICS.ITCS.2019.59}, volume = {124}, year = {2018}, } @article{742, abstract = {We give a detailed and easily accessible proof of Gromov’s Topological Overlap Theorem. Let X be a finite simplicial complex or, more generally, a finite polyhedral cell complex of dimension d. Informally, the theorem states that if X has sufficiently strong higher-dimensional expansion properties (which generalize edge expansion of graphs and are defined in terms of cellular cochains of X) then X has the following topological overlap property: for every continuous map (Formula presented.) there exists a point (Formula presented.) that is contained in the images of a positive fraction (Formula presented.) of the d-cells of X. More generally, the conclusion holds if (Formula presented.) is replaced by any d-dimensional piecewise-linear manifold M, with a constant (Formula presented.) that depends only on d and on the expansion properties of X, but not on M.}, author = {Dotterrer, Dominic and Kaufman, Tali and Wagner, Uli}, journal = {Geometriae Dedicata}, number = {1}, pages = {307–317}, publisher = {Springer}, title = {{On expansion and topological overlap}}, doi = {10.1007/s10711-017-0291-4}, volume = {195}, year = {2018}, } @unpublished{75, abstract = {We prove that any convex body in the plane can be partitioned into m convex parts of equal areas and perimeters for any integer m≥2; this result was previously known for prime powers m=pk. We also give a higher-dimensional generalization.}, author = {Akopyan, Arseniy and Avvakumov, Sergey and Karasev, Roman}, publisher = {arXiv}, title = {{Convex fair partitions into arbitrary number of pieces}}, doi = {10.48550/arXiv.1804.03057}, year = {2018}, } @article{9915, abstract = {The evolution of assortative mating is a key part of the speciation process. Stronger assortment, or greater divergence in mating traits, between species pairs with overlapping ranges is commonly observed, but possible causes of this pattern of reproductive character displacement are difficult to distinguish. We use a multidisciplinary approach to provide a rare example where it is possible to distinguish among hypotheses concerning the evolution of reproductive character displacement. We build on an earlier comparative analysis that illustrated a strong pattern of greater divergence in penis form between pairs of sister species with overlapping ranges than between allopatric sister-species pairs, in a large clade of marine gastropods (Littorinidae). We investigate both assortative mating and divergence in male genitalia in one of the sister-species pairs, discriminating among three contrasting processes each of which can generate a pattern of reproductive character displacement: reinforcement, reproductive interference and the Templeton effect. We demonstrate reproductive character displacement in assortative mating, but not in genital form between this pair of sister species and use demographic models to distinguish among the different processes. Our results support a model with no gene flow since secondary contact and thus favor reproductive interference as the cause of reproductive character displacement for mate choice, rather than reinforcement. High gene flow within species argues against the Templeton effect. Secondary contact appears to have had little impact on genital divergence.}, author = {Hollander, Johan and Montaño-Rendón, Mauricio and Bianco, Giuseppe and Yang, Xi and Westram, Anja M and Duvaux, Ludovic and Reid, David G. and Butlin, Roger K.}, issn = {2056-3744}, journal = {Evolution Letters}, number = {6}, pages = {557--566}, publisher = {Wiley}, title = {{Are assortative mating and genital divergence driven by reinforcement?}}, doi = {10.1002/evl3.85}, volume = {2}, year = {2018}, } @article{9917, abstract = {Adaptive divergence and speciation may happen despite opposition by gene flow. Identifying the genomic basis underlying divergence with gene flow is a major task in evolutionary genomics. Most approaches (e.g., outlier scans) focus on genomic regions of high differentiation. However, not all genomic architectures potentially underlying divergence are expected to show extreme differentiation. Here, we develop an approach that combines hybrid zone analysis (i.e., focuses on spatial patterns of allele frequency change) with system-specific simulations to identify loci inconsistent with neutral evolution. We apply this to a genome-wide SNP set from an ideally suited study organism, the intertidal snail Littorina saxatilis, which shows primary divergence between ecotypes associated with different shore habitats. We detect many SNPs with clinal patterns, most of which are consistent with neutrality. Among non-neutral SNPs, most are located within three large putative inversions differentiating ecotypes. Many non-neutral SNPs show relatively low levels of differentiation. We discuss potential reasons for this pattern, including loose linkage to selected variants, polygenic adaptation and a component of balancing selection within populations (which may be expected for inversions). Our work is in line with theory predicting a role for inversions in divergence, and emphasizes that genomic regions contributing to divergence may not always be accessible with methods purely based on allele frequency differences. These conclusions call for approaches that take spatial patterns of allele frequency change into account in other systems.}, author = {Westram, Anja M and Rafajlović, Marina and Chaube, Pragya and Faria, Rui and Larsson, Tomas and Panova, Marina and Ravinet, Mark and Blomberg, Anders and Mehlig, Bernhard and Johannesson, Kerstin and Butlin, Roger}, issn = {2056-3744}, journal = {Evolution Letters}, number = {4}, pages = {297--309}, publisher = {Wiley}, title = {{Clines on the seashore: The genomic architecture underlying rapid divergence in the face of gene flow}}, doi = {10.1002/evl3.74}, volume = {2}, year = {2018}, } @misc{9929, abstract = {The evolution of assortative mating is a key part of the speciation process. Stronger assortment, or greater divergence in mating traits, between species pairs with overlapping ranges is commonly observed, but possible causes of this pattern of reproductive character displacement are difficult to distinguish. We use a multidisciplinary approach to provide a rare example where it is possible to distinguish among hypotheses concerning the evolution of reproductive character displacement. We build on an earlier comparative analysis that illustrated a strong pattern of greater divergence in penis form between pairs of sister species with overlapping ranges than between allopatric sister-species pairs, in a large clade of marine gastropods (Littorinidae). We investigate both assortative mating and divergence in male genitalia in one of the sister-species pairs, discriminating among three contrasting processes each of which can generate a pattern of reproductive character displacement: reinforcement, reproductive interference and the Templeton effect. We demonstrate reproductive character displacement in assortative mating, but not in genital form between this pair of sister species and use demographic models to distinguish among the different processes. Our results support a model with no gene flow since secondary contact and thus favour reproductive interference as the cause of reproductive character displacement for mate choice, rather than reinforcement. High gene flow within species argues against the Templeton effect. Secondary contact appears to have had little impact on genital divergence.}, author = {Hollander, Johan and Montaño-Rendón, Mauricio and Bianco, Giuseppe and Yang, Xi and Westram, Anja M and Duvaux, Ludovic and Reid, David G. and Butlin, Roger K.}, publisher = {Dryad}, title = {{Data from: Are assortative mating and genital divergence driven by reinforcement?}}, doi = {10.5061/dryad.51sd2p5}, year = {2018}, } @misc{9930, abstract = {Adaptive divergence and speciation may happen despite opposition by gene flow. Identifying the genomic basis underlying divergence with gene flow is a major task in evolutionary genomics. Most approaches (e.g. outlier scans) focus on genomic regions of high differentiation. However, not all genomic architectures potentially underlying divergence are expected to show extreme differentiation. Here, we develop an approach that combines hybrid zone analysis (i.e. focuses on spatial patterns of allele frequency change) with system-specific simulations to identify loci inconsistent with neutral evolution. We apply this to a genome-wide SNP set from an ideally-suited study organism, the intertidal snail Littorina saxatilis, which shows primary divergence between ecotypes associated with different shore habitats. We detect many SNPs with clinal patterns, most of which are consistent with neutrality. Among non-neutral SNPs, most are located within three large putative inversions differentiating ecotypes. Many non-neutral SNPs show relatively low levels of differentiation. We discuss potential reasons for this pattern, including loose linkage to selected variants, polygenic adaptation and a component of balancing selection within populations (which may be expected for inversions). Our work is in line with theory predicting a role for inversions in divergence, and emphasises that genomic regions contributing to divergence may not always be accessible with methods purely based on allele frequency differences. These conclusions call for approaches that take spatial patterns of allele frequency change into account in other systems.}, author = {Westram, Anja M and Rafajlović, Marina and Chaube, Pragya and Faria, Rui and Larsson, Tomas and Panova, Marina and Ravinet, Mark and Blomberg, Anders and Mehlig, Bernhard and Johannesson, Kerstin and Butlin, Roger}, publisher = {Dryad}, title = {{Data from: Clines on the seashore: the genomic architecture underlying rapid divergence in the face of gene flow}}, doi = {10.5061/dryad.bp25b65}, year = {2018}, } @inproceedings{309, abstract = {We present an efficient algorithm for a problem in the interface between clustering and graph embeddings. An embedding ' : G ! M of a graph G into a 2manifold M maps the vertices in V (G) to distinct points and the edges in E(G) to interior-disjoint Jordan arcs between the corresponding vertices. In applications in clustering, cartography, and visualization, nearby vertices and edges are often bundled to a common node or arc, due to data compression or low resolution. This raises the computational problem of deciding whether a given map ' : G ! M comes from an embedding. A map ' : G ! M is a weak embedding if it can be perturbed into an embedding ψ: G ! M with k' "k < " for every " > 0. A polynomial-time algorithm for recognizing weak embeddings was recently found by Fulek and Kyncl [14], which reduces to solving a system of linear equations over Z2. It runs in O(n2!) O(n4:75) time, where 2:373 is the matrix multiplication exponent and n is the number of vertices and edges of G. We improve the running time to O(n log n). Our algorithm is also conceptually simpler than [14]: We perform a sequence of local operations that gradually "untangles" the image '(G) into an embedding (G), or reports that ' is not a weak embedding. It generalizes a recent technique developed for the case that G is a cycle and the embedding is a simple polygon [1], and combines local constraints on the orientation of subgraphs directly, thereby eliminating the need for solving large systems of linear equations.}, author = {Akitaya, Hugo and Fulek, Radoslav and Tóth, Csaba}, location = {New Orleans, LA, USA}, pages = {274 -- 292}, publisher = {ACM}, title = {{Recognizing weak embeddings of graphs}}, doi = {10.1137/1.9781611975031.20}, year = {2018}, } @article{31, abstract = {Correlations in sensory neural networks have both extrinsic and intrinsic origins. Extrinsic or stimulus correlations arise from shared inputs to the network and, thus, depend strongly on the stimulus ensemble. Intrinsic or noise correlations reflect biophysical mechanisms of interactions between neurons, which are expected to be robust to changes in the stimulus ensemble. Despite the importance of this distinction for understanding how sensory networks encode information collectively, no method exists to reliably separate intrinsic interactions from extrinsic correlations in neural activity data, limiting our ability to build predictive models of the network response. In this paper we introduce a general strategy to infer population models of interacting neurons that collectively encode stimulus information. The key to disentangling intrinsic from extrinsic correlations is to infer the couplings between neurons separately from the encoding model and to combine the two using corrections calculated in a mean-field approximation. We demonstrate the effectiveness of this approach in retinal recordings. The same coupling network is inferred from responses to radically different stimulus ensembles, showing that these couplings indeed reflect stimulus-independent interactions between neurons. The inferred model predicts accurately the collective response of retinal ganglion cell populations as a function of the stimulus.}, author = {Ferrari, Ulisse and Deny, Stephane and Chalk, Matthew J and Tkacik, Gasper and Marre, Olivier and Mora, Thierry}, issn = {2470-0045}, journal = {Physical Review E}, number = {4}, publisher = {American Physical Society}, title = {{Separating intrinsic interactions from extrinsic correlations in a network of sensory neurons}}, doi = {10.1103/PhysRevE.98.042410}, volume = {98}, year = {2018}, } @inproceedings{310, abstract = {A model of computation that is widely used in the formal analysis of reactive systems is symbolic algorithms. In this model the access to the input graph is restricted to consist of symbolic operations, which are expensive in comparison to the standard RAM operations. We give lower bounds on the number of symbolic operations for basic graph problems such as the computation of the strongly connected components and of the approximate diameter as well as for fundamental problems in model checking such as safety, liveness, and coliveness. Our lower bounds are linear in the number of vertices of the graph, even for constant-diameter graphs. For none of these problems lower bounds on the number of symbolic operations were known before. The lower bounds show an interesting separation of these problems from the reachability problem, which can be solved with O(D) symbolic operations, where D is the diameter of the graph. Additionally we present an approximation algorithm for the graph diameter which requires Õ(n/D) symbolic steps to achieve a (1 +ϵ)-approximation for any constant > 0. This compares to O(n/D) symbolic steps for the (naive) exact algorithm and O(D) symbolic steps for a 2-approximation. Finally we also give a refined analysis of the strongly connected components algorithms of [15], showing that it uses an optimal number of symbolic steps that is proportional to the sum of the diameters of the strongly connected components.}, author = {Chatterjee, Krishnendu and Dvorák, Wolfgang and Henzinger, Monika H and Loitzenbauer, Veronika}, location = {New Orleans, Louisiana, United States}, pages = {2341 -- 2356}, publisher = {ACM}, title = {{Lower bounds for symbolic computation on graphs: Strongly connected components, liveness, safety, and diameter}}, doi = {10.1137/1.9781611975031.151}, year = {2018}, } @article{314, abstract = {The interface of physics and biology pro-vides a fruitful environment for generatingnew concepts and exciting ways forwardto understanding living matter. Examplesof successful studies include the estab-lishment and readout of morphogen gra-dients during development, signal pro-cessing in protein and genetic networks,the role of fluctuations in determining thefates of cells and tissues, and collectiveeffects in proteins and in tissues. It is nothard to envision that significant further ad-vances will translate to societal benefitsby initiating the development of new de-vices and strategies for curing disease.However, research at the interface posesvarious challenges, in particular for youngscientists, and current institutions arerarely designed to facilitate such scientificprograms. In this Letter, we propose aninternational initiative that addressesthese challenges through the establish-ment of a worldwide network of platformsfor cross-disciplinary training and incuba-tors for starting new collaborations.}, author = {Bauer, Guntram and Fakhri, Nikta and Kicheva, Anna and Kondev, Jané and Kruse, Karsten and Noji, Hiroyuki and Riveline, Daniel and Saunders, Timothy and Thatta, Mukund and Wieschaus, Eric}, issn = {2405-4712}, journal = {Cell Systems}, number = {4}, pages = {400 -- 402}, publisher = {Cell Press}, title = {{The science of living matter for tomorrow}}, doi = {10.1016/j.cels.2018.04.003}, volume = {6}, year = {2018}, } @article{315, abstract = {More than 100 years after Grigg’s influential analysis of species’ borders, the causes of limits to species’ ranges still represent a puzzle that has never been understood with clarity. The topic has become especially important recently as many scientists have become interested in the potential for species’ ranges to shift in response to climate change—and yet nearly all of those studies fail to recognise or incorporate evolutionary genetics in a way that relates to theoretical developments. I show that range margins can be understood based on just two measurable parameters: (i) the fitness cost of dispersal—a measure of environmental heterogeneity—and (ii) the strength of genetic drift, which reduces genetic diversity. Together, these two parameters define an ‘expansion threshold’: adaptation fails when genetic drift reduces genetic diversity below that required for adaptation to a heterogeneous environment. When the key parameters drop below this expansion threshold locally, a sharp range margin forms. When they drop below this threshold throughout the species’ range, adaptation collapses everywhere, resulting in either extinction or formation of a fragmented metapopulation. Because the effects of dispersal differ fundamentally with dimension, the second parameter—the strength of genetic drift—is qualitatively different compared to a linear habitat. In two-dimensional habitats, genetic drift becomes effectively independent of selection. It decreases with ‘neighbourhood size’—the number of individuals accessible by dispersal within one generation. Moreover, in contrast to earlier predictions, which neglected evolution of genetic variance and/or stochasticity in two dimensions, dispersal into small marginal populations aids adaptation. This is because the reduction of both genetic and demographic stochasticity has a stronger effect than the cost of dispersal through increased maladaptation. The expansion threshold thus provides a novel, theoretically justified, and testable prediction for formation of the range margin and collapse of the species’ range.}, author = {Polechova, Jitka}, issn = {1544-9173}, journal = {PLoS Biology}, number = {6}, publisher = {Public Library of Science}, title = {{Is the sky the limit? On the expansion threshold of a species’ range}}, doi = {10.1371/journal.pbio.2005372}, volume = {16}, year = {2018}, } @article{316, abstract = {Self-incompatibility (SI) is a genetically based recognition system that functions to prevent self-fertilization and mating among related plants. An enduring puzzle in SI is how the high diversity observed in nature arises and is maintained. Based on the underlying recognition mechanism, SI can be classified into two main groups: self- and non-self recognition. Most work has focused on diversification within self-recognition systems despite expected differences between the two groups in the evolutionary pathways and outcomes of diversification. Here, we use a deterministic population genetic model and stochastic simulations to investigate how novel S-haplotypes evolve in a gametophytic non-self recognition (SRNase/S Locus F-box (SLF)) SI system. For this model the pathways for diversification involve either the maintenance or breakdown of SI and can vary in the order of mutations of the female (SRNase) and male (SLF) components. We show analytically that diversification can occur with high inbreeding depression and self-pollination, but this varies with evolutionary pathway and level of completeness (which determines the number of potential mating partners in the population), and in general is more likely for lower haplotype number. The conditions for diversification are broader in stochastic simulations of finite population size. However, the number of haplotypes observed under high inbreeding and moderate to high self-pollination is less than that commonly observed in nature. Diversification was observed through pathways that maintain SI as well as through self-compatible intermediates. Yet the lifespan of diversified haplotypes was sensitive to their level of completeness. By examining diversification in a non-self recognition SI system, this model extends our understanding of the evolution and maintenance of haplotype diversity observed in a self recognition system common in flowering plants.}, author = {Bodova, Katarina and Priklopil, Tadeas and Field, David and Barton, Nicholas H and Pickup, Melinda}, journal = {Genetics}, number = {3}, pages = {861--883}, publisher = {Genetics Society of America}, title = {{Evolutionary pathways for the generation of new self-incompatibility haplotypes in a non-self recognition system}}, doi = {10.1534/genetics.118.300748}, volume = {209}, year = {2018}, } @article{317, abstract = {We replace the established aluminium gates for the formation of quantum dots in silicon with gates made from palladium. We study the morphology of both aluminium and palladium gates with transmission electron microscopy. The native aluminium oxide is found to be formed all around the aluminium gates, which could lead to the formation of unintentional dots. Therefore, we report on a novel fabrication route that replaces aluminium and its native oxide by palladium with atomic-layer-deposition-grown aluminium oxide. Using this approach, we show the formation of low-disorder gate-defined quantum dots, which are reproducibly fabricated. Furthermore, palladium enables us to further shrink the gate design, allowing us to perform electron transport measurements in the few-electron regime in devices comprising only two gate layers, a major technological advancement. It remains to be seen, whether the introduction of palladium gates can improve the excellent results on electron and nuclear spin qubits defined with an aluminium gate stack.}, author = {Brauns, Matthias and Amitonov, Sergey and Spruijtenburg, Paul and Zwanenburg, Floris}, journal = {Scientific Reports}, number = {1}, publisher = {Nature Publishing Group}, title = {{Palladium gates for reproducible quantum dots in silicon}}, doi = {10.1038/s41598-018-24004-y}, volume = {8}, year = {2018}, } @article{318, abstract = {The insect’s fat body combines metabolic and immunological functions. In this issue of Developmental Cell, Franz et al. (2018) show that in Drosophila, cells of the fat body are not static, but can actively “swim” toward sites of epithelial injury, where they physically clog the wound and locally secrete antimicrobial peptides.}, author = {Casano, Alessandra M and Sixt, Michael K}, journal = {Developmental Cell}, number = {4}, pages = {405 -- 406}, publisher = {Cell Press}, title = {{A fat lot of good for wound healing}}, doi = {10.1016/j.devcel.2018.02.009}, volume = {44}, year = {2018}, } @article{32, abstract = {The functional role of AMPA receptor (AMPAR)-mediated synaptic signaling between neurons and oligodendrocyte precursor cells (OPCs) remains enigmatic. We modified the properties of AMPARs at axon-OPC synapses in the mouse corpus callosum in vivo during the peak of myelination by targeting the GluA2 subunit. Expression of the unedited (Ca2+ permeable) or the pore-dead GluA2 subunit of AMPARs triggered proliferation of OPCs and reduced their differentiation into oligodendrocytes. Expression of the cytoplasmic C-terminal (GluA2(813-862)) of the GluA2 subunit (C-tail), a modification designed to affect the interaction between GluA2 and AMPAR-binding proteins and to perturb trafficking of GluA2-containing AMPARs, decreased the differentiation of OPCs without affecting their proliferation. These findings suggest that ionotropic and non-ionotropic properties of AMPARs in OPCs, as well as specific aspects of AMPAR-mediated signaling at axon-OPC synapses in the mouse corpus callosum, are important for balancing the response of OPCs to proliferation and differentiation cues. In the brain, oligodendrocyte precursor cells (OPCs) receive glutamatergic AMPA-receptor-mediated synaptic input from neurons. Chen et al. show that modifying AMPA-receptor properties at axon-OPC synapses alters proliferation and differentiation of OPCs. This expands the traditional view of synaptic transmission by suggesting neurons also use synapses to modulate behavior of glia.}, author = {Chen, Ting and Kula, Bartosz and Nagy, Balint and Barzan, Ruxandra and Gall, Andrea and Ehrlich, Ingrid and Kukley, Maria}, journal = {Cell Reports}, number = {4}, pages = {852 -- 861.e7}, publisher = {Elsevier}, title = {{In Vivo regulation of Oligodendrocyte processor cell proliferation and differentiation by the AMPA-receptor Subunit GluA2}}, doi = {10.1016/j.celrep.2018.09.066}, volume = {25}, year = {2018}, }