TY - JOUR AB - Flow chemistry involves the use of channels or tubing to conduct a reaction in a continuous stream rather than in a flask. Flow equipment provides chemists with unique control over reaction parameters enhancing reactivity or in some cases enabling new reactions. This relatively young technology has received a remarkable amount of attention in the past decade with many reports on what can be done in flow. Until recently, however, the question, “Should we do this in flow?” has merely been an afterthought. This review introduces readers to the basic principles and fundamentals of flow chemistry and critically discusses recent flow chemistry accounts. AU - Plutschack, Matthew B. AU - Pieber, Bartholomäus AU - Gilmore, Kerry AU - Seeberger, Peter H. ID - 11961 IS - 18 JF - Chemical Reviews SN - 0009-2665 TI - The Hitchhiker’s Guide to flow chemistry VL - 117 ER - TY - JOUR AB - The way organic multistep synthesis is performed is changing due to the adoption of flow chemical techniques, which has enabled the development of improved methods to make complex molecules. The modular nature of the technique provides not only access to target molecules via linear flow approaches but also for the targeting of structural cores with single systems. This perspective article summarizes the state of the art of continuous multistep synthesis and discusses the main challenges and opportunities in this area. AU - Pieber, Bartholomäus AU - Gilmore, Kerry AU - Seeberger, Peter H. ID - 11976 IS - 3-4 JF - Journal of Flow Chemistry SN - 2062-249X TI - Integrated flow processing - challenges in continuous multistep synthesis VL - 7 ER - TY - JOUR AB - Systems such as fluid flows in channels and pipes or the complex Ginzburg–Landau system, defined over periodic domains, exhibit both continuous symmetries, translational and rotational, as well as discrete symmetries under spatial reflections or complex conjugation. The simplest, and very common symmetry of this type is the equivariance of the defining equations under the orthogonal group O(2). We formulate a novel symmetry reduction scheme for such systems by combining the method of slices with invariant polynomial methods, and show how it works by applying it to the Kuramoto–Sivashinsky system in one spatial dimension. As an example, we track a relative periodic orbit through a sequence of bifurcations to the onset of chaos. Within the symmetry-reduced state space we are able to compute and visualize the unstable manifolds of relative periodic orbits, their torus bifurcations, a transition to chaos via torus breakdown, and heteroclinic connections between various relative periodic orbits. It would be very hard to carry through such analysis in the full state space, without a symmetry reduction such as the one we present here. AU - Budanur, Nazmi B AU - Cvitanović, Predrag ID - 1211 IS - 3-4 JF - Journal of Statistical Physics TI - Unstable manifolds of relative periodic orbits in the symmetry reduced state space of the Kuramoto–Sivashinsky system VL - 167 ER - TY - JOUR AB - The Leidenfrost effect occurs when an object near a hot surface vaporizes rapidly enough to lift itself up and hover. Although well understood for liquids and stiff sublimable solids, nothing is known about the effect with materials whose stiffness lies between these extremes. Here we introduce a new phenomenon that occurs with vaporizable soft solids - the elastic Leidenfrost effect. By dropping hydrogel spheres onto hot surfaces we find that, rather than hovering, they energetically bounce several times their diameter for minutes at a time. With high-speed video during a single impact, we uncover high-frequency microscopic gap dynamics at the sphere/substrate interface. We show how these otherwise-hidden agitations constitute work cycles that harvest mechanical energy from the vapour and sustain the bouncing. Our findings suggest a new strategy for injecting mechanical energy into a widely used class of soft materials, with potential relevance to fields such as active matter, soft robotics and microfluidics. AU - Waitukaitis, Scott R AU - Zuiderwijk, Antal AU - Souslov, Anton AU - Coulais, Corentin AU - Van Hecke, Martin ID - 123 IS - 11 JF - Nature Physics TI - Coupling the Leidenfrost effect and elastic deformations to power sustained bouncing VL - 13 ER - TY - CONF AB - We consider the problems of maintaining approximate maximum matching and minimum vertex cover in a dynamic graph. Starting with the seminal work of Onak and Rubinfeld [STOC 2010], this problem has received significant attention in recent years. Very recently, extending the framework of Baswana, Gupta and Sen [FOCS 2011], Solomon [FOCS 2016] gave a randomized 2-approximation dynamic algorithm for this problem that has amortized update time of O(1) with high probability. We consider the natural open question of derandomizing this result. We present a new deterministic fully dynamic algorithm that maintains a O(1)-approximate minimum vertex cover and maximum fractional matching, with an amortized update time of O(1). Previously, the best deterministic algorithm for this problem was due to Bhattacharya, Henzinger and Italiano [SODA 2015]; it had an approximation ratio of (2+ϵ) and an amortized update time of O(logn/ϵ2). Our result can be generalized to give a fully dynamic O(f3)-approximation algorithm with O(f2) amortized update time for the hypergraph vertex cover and fractional matching problems, where every hyperedge has at most f vertices. AU - Bhattacharya, Sayan AU - Chakrabarty, Deeparnab AU - Henzinger, Monika H ID - 12571 SN - 0302-9743 T2 - 19th International Conference on Integer Programming and Combinatorial Optimization TI - Deterministic fully dynamic approximate vertex cover and fractional matching in O(1) amortized update time VL - 10328 ER - TY - JOUR AB - A drawing of a graph G is radial if the vertices of G are placed on concentric circles C 1 , . . . , C k with common center c , and edges are drawn radially : every edge intersects every circle centered at c at most once. G is radial planar if it has a radial embedding, that is, a crossing-free radial drawing. If the vertices of G are ordered or partitioned into ordered levels (as they are for leveled graphs), we require that the assignment of vertices to circles corresponds to the given ordering or leveling. We show that a graph G is radial planar if G has a radial drawing in which every two edges cross an even number of times; the radial embedding has the same leveling as the radial drawing. In other words, we establish the weak variant of the Hanani-Tutte theorem for radial planarity. This generalizes a result by Pach and Toth. AU - Fulek, Radoslav AU - Pelsmajer, Michael AU - Schaefer, Marcus ID - 1113 IS - 1 JF - Journal of Graph Algorithms and Applications TI - Hanani-Tutte for radial planarity VL - 21 ER - TY - JOUR AB - We show that a twisted variant of Linnik’s conjecture on sums of Kloosterman sums leads to an optimal covering exponent for S3. AU - Browning, Timothy D AU - Kumaraswamy, Vinay AU - Steiner, Rapael ID - 169 JF - International Mathematics Research Notices TI - Twisted Linnik implies optimal covering exponent for S3 ER - TY - JOUR AB - We study strong approximation for some algebraic varieties over ℚ which are defined using norm forms. This allows us to confirm a special case of a conjecture due to Harpaz and Wittenberg. AU - Browning, Timothy D AU - Schindler, Damaris ID - 172 JF - International Mathematics Research Notices TI - Strong approximation and a conjecture of Harpaz and Wittenberg ER - TY - JOUR AB - Three-dimensional topological insulators are bulk insulators with Z 2 topological electronic order that gives rise to conducting light-like surface states. These surface electrons are exceptionally resistant to localization by non-magnetic disorder, and have been adopted as the basis for a wide range of proposals to achieve new quasiparticle species and device functionality. Recent studies have yielded a surprise by showing that in spite of resisting localization, topological insulator surface electrons can be reshaped by defects into distinctive resonance states. Here we use numerical simulations and scanning tunnelling microscopy data to show that these resonance states have significance well beyond the localized regime usually associated with impurity bands. At native densities in the model Bi2X3 (X=Bi, Te) compounds, defect resonance states are predicted to generate a new quantum basis for an emergent electron gas that supports diffusive electrical transport. AU - Xu, Yishuai AU - Chiu, Janet AU - Miao, Lin AU - He, Haowei AU - Alpichshev, Zhanybek AU - Kapitulnik, Aharon AU - Biswas, Rudro AU - Wray, Lewis ID - 391 JF - Nature Communications TI - Disorder enabled band structure engineering of a topological insulator surface VL - 8 ER - TY - JOUR AB - We use a three-pulse ultrafast optical spectroscopy to study the relaxation processes in a frustrated Mott insulator Na2IrO3. By being able to independently produce the out-of-equilibrium bound states (excitons) of doublons and holons with the first pulse and suppress the underlying antiferromagnetic order with the second one, we were able to elucidate the relaxation mechanism of quasiparticles in this system. By observing the difference in the exciton dynamics in the magnetically ordered and disordered phases we found that the mass of this quasiparticle is mostly determined by its interaction with the surrounding spins. AU - Alpichshev, Zhanybek AU - Sie, Edbert AU - Mahmood, Fahad AU - Cao, Gang AU - Gedik, Nuh ID - 393 IS - 23 JF - Physical Review B TI - Origin of the exciton mass in the frustrated Mott insulator Na2IrO3 VL - 96 ER -