TY - CONF
AB - matching is compatible to two or more labeled point sets of size n with labels {1,…,n} if its straight-line drawing on each of these point sets is crossing-free. We study the maximum number of edges in a matching compatible to two or more labeled point sets in general position in the plane. We show that for any two labeled convex sets of n points there exists a compatible matching with ⌊2n−−√⌋ edges. More generally, for any ℓ labeled point sets we construct compatible matchings of size Ω(n1/ℓ) . As a corresponding upper bound, we use probabilistic arguments to show that for any ℓ given sets of n points there exists a labeling of each set such that the largest compatible matching has O(n2/(ℓ+1)) edges. Finally, we show that Θ(logn) copies of any set of n points are necessary and sufficient for the existence of a labeling such that any compatible matching consists only of a single edge.
AU - Aichholzer, Oswin
AU - Arroyo Guevara, Alan M
AU - Masárová, Zuzana
AU - Parada, Irene
AU - Perz, Daniel
AU - Pilz, Alexander
AU - Tkadlec, Josef
AU - Vogtenhuber, Birgit
ID - 9296
SN - 03029743
T2 - 15th International Conference on Algorithms and Computation
TI - On compatible matchings
VL - 12635
ER -
TY - JOUR
AB - We report the results of an experimental investigation into the decay of turbulence in plane Couette–Poiseuille flow using ‘quench’ experiments where the flow laminarises after a sudden reduction in Reynolds number Re. Specifically, we study the velocity field in the streamwise–spanwise plane. We show that the spanwise velocity containing rolls decays faster than the streamwise velocity, which displays elongated regions of higher or lower velocity called streaks. At final Reynolds numbers above 425, the decay of streaks displays two stages: first a slow decay when rolls are present and secondly a more rapid decay of streaks alone. The difference in behaviour results from the regeneration of streaks by rolls, called the lift-up effect. We define the turbulent fraction as the portion of the flow containing turbulence and this is estimated by thresholding the spanwise velocity component. It decreases linearly with time in the whole range of final Re. The corresponding decay slope increases linearly with final Re. The extrapolated value at which this decay slope vanishes is Reaz≈656±10, close to Reg≈670 at which turbulence is self-sustained. The decay of the energy computed from the spanwise velocity component is found to be exponential. The corresponding decay rate increases linearly with Re, with an extrapolated vanishing value at ReAz≈688±10. This value is also close to the value at which the turbulence is self-sustained, showing that valuable information on the transition can be obtained over a wide range of Re.
AU - Liu, T.
AU - Semin, B.
AU - Klotz, Lukasz
AU - Godoy-Diana, R.
AU - Wesfreid, J. E.
AU - Mullin, T.
ID - 9297
JF - Journal of Fluid Mechanics
SN - 0022-1120
TI - Decay of streaks and rolls in plane Couette-Poiseuille flow
VL - 915
ER -
TY - JOUR
AB - Hill's Conjecture states that the crossing number cr(𝐾𝑛) of the complete graph 𝐾𝑛 in the plane (equivalently, the sphere) is 14⌊𝑛2⌋⌊𝑛−12⌋⌊𝑛−22⌋⌊𝑛−32⌋=𝑛4/64+𝑂(𝑛3) . Moon proved that the expected number of crossings in a spherical drawing in which the points are randomly distributed and joined by geodesics is precisely 𝑛4/64+𝑂(𝑛3) , thus matching asymptotically the conjectured value of cr(𝐾𝑛) . Let cr𝑃(𝐺) denote the crossing number of a graph 𝐺 in the projective plane. Recently, Elkies proved that the expected number of crossings in a naturally defined random projective plane drawing of 𝐾𝑛 is (𝑛4/8𝜋2)+𝑂(𝑛3) . In analogy with the relation of Moon's result to Hill's conjecture, Elkies asked if lim𝑛→∞ cr𝑃(𝐾𝑛)/𝑛4=1/8𝜋2 . We construct drawings of 𝐾𝑛 in the projective plane that disprove this.
AU - Arroyo Guevara, Alan M
AU - Mcquillan, Dan
AU - Richter, R. Bruce
AU - Salazar, Gelasio
AU - Sullivan, Matthew
ID - 9295
JF - Journal of Graph Theory
SN - 0364-9024
TI - Drawings of complete graphs in the projective plane
ER -
TY - JOUR
AB - We consider planning problems for graphs, Markov Decision Processes (MDPs), and games on graphs in an explicit state space. While graphs represent the most basic planning model, MDPs represent interaction with nature and games on graphs represent interaction with an adversarial environment. We consider two planning problems with k different target sets: (a) the coverage problem asks whether there is a plan for each individual target set; and (b) the sequential target reachability problem asks whether the targets can be reached in a given sequence. For the coverage problem, we present a linear-time algorithm for graphs, and quadratic conditional lower bound for MDPs and games on graphs. For the sequential target problem, we present a linear-time algorithm for graphs, a sub-quadratic algorithm for MDPs, and a quadratic conditional lower bound for games on graphs. Our results with conditional lower bounds, based on the boolean matrix multiplication (BMM) conjecture and strong exponential time hypothesis (SETH), establish (i) model-separation results showing that for the coverage problem MDPs and games on graphs are harder than graphs, and for the sequential reachability problem games on graphs are harder than MDPs and graphs; and (ii) problem-separation results showing that for MDPs the coverage problem is harder than the sequential target problem.
AU - Chatterjee, Krishnendu
AU - Dvořák, Wolfgang
AU - Henzinger, Monika
AU - Svozil, Alexander
ID - 9293
IS - 8
JF - Artificial Intelligence
SN - 00043702
TI - Algorithms and conditional lower bounds for planning problems
VL - 297
ER -
TY - JOUR
AB - In this issue of Developmental Cell, Doyle and colleagues identify periodic anterior contraction as a characteristic feature of fibroblasts and mesenchymal cancer cells embedded in 3D collagen gels. This contractile mechanism generates a matrix prestrain required for crawling in fibrous 3D environments.
AU - Gärtner, Florian R
AU - Sixt, Michael K
ID - 9294
IS - 6
JF - Developmental Cell
SN - 15345807
TI - Engaging the front wheels to drive through fibrous terrain
VL - 56
ER -
TY - JOUR
AB - We establish finite time extinction with probability one for weak solutions of the Cauchy–Dirichlet problem for the 1D stochastic porous medium equation with Stratonovich transport noise and compactly supported smooth initial datum. Heuristically, this is expected to hold because Brownian motion has average spread rate O(t12) whereas the support of solutions to the deterministic PME grows only with rate O(t1m+1). The rigorous proof relies on a contraction principle up to time-dependent shift for Wong–Zakai type approximations, the transformation to a deterministic PME with two copies of a Brownian path as the lateral boundary, and techniques from the theory of viscosity solutions.
AU - Hensel, Sebastian
ID - 9307
JF - Stochastics and Partial Differential Equations: Analysis and Computations
SN - 21940401
TI - Finite time extinction for the 1D stochastic porous medium equation with transport noise
ER -
TY - JOUR
AB - The high processing cost, poor mechanical properties and moderate performance of Bi2Te3–based alloys used in thermoelectric devices limit the cost-effectiveness of this energy conversion technology. Towards solving these current challenges, in the present work, we detail a low temperature solution-based approach to produce Bi2Te3-Cu2-xTe nanocomposites with improved thermoelectric performance. Our approach consists in combining proper ratios of colloidal nanoparticles and to consolidate the resulting mixture into nanocomposites using a hot press. The transport properties of the nanocomposites are characterized and compared with those of pure Bi2Te3 nanomaterials obtained following the same procedure. In contrast with most previous works, the presence of Cu2-xTe nanodomains does not result in a significant reduction of the lattice thermal conductivity of the reference Bi2Te3 nanomaterial, which is already very low. However, the introduction of Cu2-xTe yields a nearly threefold increase of the power factor associated to a simultaneous increase of the Seebeck coefficient and electrical conductivity at temperatures above 400 K. Taking into account the band alignment of the two materials, we rationalize this increase by considering that Cu2-xTe nanostructures, with a relatively low electron affinity, are able to inject electrons into Bi2Te3, enhancing in this way its electrical conductivity. The simultaneous increase of the Seebeck coefficient is related to the energy filtering of charge carriers at energy barriers within Bi2Te3 domains associated with the accumulation of electrons in regions nearby a Cu2-xTe/Bi2Te3 heterojunction. Overall, with the incorporation of a proper amount of Cu2-xTe nanoparticles, we demonstrate a 250% improvement of the thermoelectric figure of merit of Bi2Te3.
AU - Zhang, Yu
AU - Xing, Congcong
AU - Liu, Yu
AU - Li, Mengyao
AU - Xiao, Ke
AU - Guardia, Pablo
AU - Lee, Seungho
AU - Han, Xu
AU - Ostovari Moghaddam, Ahmad
AU - Josep Roa, Joan
AU - Arbiol, Jordi
AU - Ibáñez, Maria
AU - Pan, Kai
AU - Prato, Mirko
AU - Xie, Ying
AU - Cabot, Andreu
ID - 9304
IS - 8
JF - Chemical Engineering Journal
SN - 13858947
TI - Influence of copper telluride nanodomains on the transport properties of n-type bismuth telluride
VL - 418
ER -
TY - JOUR
AB - Several Ising-type magnetic van der Waals (vdW) materials exhibit stable magnetic ground states. Despite these clear experimental demonstrations, a complete theoretical and microscopic understanding of their magnetic anisotropy is still lacking. In particular, the validity limit of identifying their one-dimensional (1-D) Ising nature has remained uninvestigated in a quantitative way. Here we performed the complete mapping of magnetic anisotropy for a prototypical Ising vdW magnet FePS3 for the first time. Combining torque magnetometry measurements with their magnetostatic model analysis and the relativistic density functional total energy calculations, we successfully constructed the three-dimensional (3-D) mappings of the magnetic anisotropy in terms of magnetic torque and energy. The results not only quantitatively confirm that the easy axis is perpendicular to the ab plane, but also reveal the anisotropies within the ab, ac, and bc planes. Our approach can be applied to the detailed quantitative study of magnetism in vdW materials.
AU - Nauman, Muhammad
AU - Kiem, Do Hoon
AU - Lee, Sungmin
AU - Son, Suhan
AU - Park, J-G
AU - Kang, Woun
AU - Han, Myung Joon
AU - Jo, Youn Jung
ID - 9282
JF - 2D Materials
KW - Mechanical Engineering
KW - General Materials Science
KW - Mechanics of Materials
KW - General Chemistry
KW - Condensed Matter Physics
SN - 2053-1583
TI - Complete mapping of magnetic anisotropy for prototype Ising van der Waals FePS3
ER -
TY - JOUR
AB - Assemblies of actin and its regulators underlie the dynamic morphology of all eukaryotic cells. To understand how actin regulatory proteins work together to generate actin-rich structures such as filopodia, we analyzed the localization of diverse actin regulators within filopodia in Drosophila embryos and in a complementary in vitro system of filopodia-like structures (FLSs). We found that the composition of the regulatory protein complex where actin is incorporated (the filopodial tip complex) is remarkably heterogeneous both in vivo and in vitro. Our data reveal that different pairs of proteins correlate with each other and with actin bundle length, suggesting the presence of functional subcomplexes. This is consistent with a theoretical framework where three or more redundant subcomplexes join the tip complex stochastically, with any two being sufficient to drive filopodia formation. We provide an explanation for the observed heterogeneity and suggest that a mechanism based on multiple components allows stereotypical filopodial dynamics to arise from diverse upstream signaling pathways.
AU - Dobramysl, Ulrich
AU - Jarsch, Iris Katharina
AU - Inoue, Yoshiko
AU - Shimo, Hanae
AU - Richier, Benjamin
AU - Gadsby, Jonathan R.
AU - Mason, Julia
AU - Szałapak, Alicja
AU - Ioannou, Pantelis Savvas
AU - Correia, Guilherme Pereira
AU - Walrant, Astrid
AU - Butler, Richard
AU - Hannezo, Edouard B
AU - Simons, Benjamin D.
AU - Gallop, Jennifer L.
ID - 9306
IS - 4
JF - The Journal of Cell Biology
TI - Stochastic combinations of actin regulatory proteins are sufficient to drive filopodia formation
VL - 220
ER -
TY - JOUR
AB - Copper chalcogenides are outstanding thermoelectric materials for applications in the medium-high temperature range. Among different chalcogenides, while Cu2−xSe is characterized by higher thermoelectric figures of merit, Cu2−xS provides advantages in terms of low cost and element abundance. In the present work, we investigate the effect of different dopants to enhance the Cu2−xS performance and also its thermal stability. Among the tested options, Pb-doped Cu2−xS shows the highest improvement in stability against sulfur volatilization. Additionally, Pb incorporation allows tuning charge carrier concentration, which enables a significant improvement of the power factor. We demonstrate here that the introduction of an optimal additive amount of just 0.3% results in a threefold increase of the power factor in the middle-temperature range (500–800 K) and a record dimensionless thermoelectric figure of merit above 2 at 880 K.
AU - Zhang, Yu
AU - Xing, Congcong
AU - Liu, Yu
AU - Spadaro, Maria Chiara
AU - Wang, Xiang
AU - Li, Mengyao
AU - Xiao, Ke
AU - Zhang, Ting
AU - Guardia, Pablo
AU - Lim, Khak Ho
AU - Moghaddam, Ahmad Ostovari
AU - Llorca, Jordi
AU - Arbiol, Jordi
AU - Ibáñez, Maria
AU - Cabot, Andreu
ID - 9305
IS - 7
JF - Nano Energy
SN - 22112855
TI - Doping-mediated stabilization of copper vacancies to promote thermoelectric properties of Cu2-xS
VL - 85
ER -