TY - THES
AB - This thesis is based on three main topics: In the first part, we study convergence of discrete gradient flow structures associated with regular finite-volume discretisations of Fokker-Planck equations. We show evolutionary I convergence of the discrete gradient flows to the L2-Wasserstein gradient flow corresponding to the solution of a Fokker-Planck
equation in arbitrary dimension d >= 1. Along the argument, we prove Mosco- and I-convergence results for discrete energy functionals, which are of independent interest for convergence of equivalent gradient flow structures in Hilbert spaces.
The second part investigates L2-Wasserstein flows on metric graph. The starting point is a Benamou-Brenier formula for the L2-Wasserstein distance, which is proved via a regularisation scheme for solutions of the continuity equation, adapted to the peculiar geometric structure of metric graphs. Based on those results, we show that the L2-Wasserstein space over a metric graph admits a gradient flow which may be identified as a solution of a Fokker-Planck equation.
In the third part, we focus again on the discrete gradient flows, already encountered in the first part. We propose a variational structure which extends the gradient flow structure to Markov chains violating the detailed-balance conditions. Using this structure, we characterise contraction estimates for the discrete heat flow in terms of convexity of
corresponding path-dependent energy functionals. In addition, we use this approach to derive several functional inequalities for said functionals.
AU - Forkert, Dominik L
ID - 7629
SN - 2663-337X
TI - Gradient flows in spaces of probability measures for finite-volume schemes, metric graphs and non-reversible Markov chains
ER -
TY - JOUR
AB - The posterior parietal cortex (PPC) and frontal motor areas comprise a cortical network supporting goal-directed behaviour, with functions including sensorimotor transformations and decision making. In primates, this network links performed and observed actions via mirror neurons, which fire both when individuals perform an action and when they observe the same action performed by a conspecific. Mirror neurons are believed to be important for social learning, but it is not known whether mirror-like neurons occur in similar networks in other social species, such as rodents, or if they can be measured in such models using paradigms where observers passively view a demonstrator. Therefore, we imaged Ca2+ responses in PPC and secondary motor cortex (M2) while mice performed and observed pellet-reaching and wheel-running tasks, and found that cell populations in both areas robustly encoded several naturalistic behaviours. However, neural responses to the same set of observed actions were absent, although we verified that observer mice were attentive to performers and that PPC neurons responded reliably to visual cues. Statistical modelling also indicated that executed actions outperformed observed actions in predicting neural responses. These results raise the possibility that sensorimotor action recognition in rodents could take place outside of the parieto-frontal circuit, and underscore that detecting socially-driven neural coding depends critically on the species and behavioural paradigm used.
AU - Tombaz, Tuce
AU - Dunn, Benjamin A.
AU - Hovde, Karoline
AU - Cubero, Ryan J
AU - Mimica, Bartul
AU - Mamidanna, Pranav
AU - Roudi, Yasser
AU - Whitlock, Jonathan R.
ID - 7632
IS - 1
JF - Scientific reports
TI - Action representation in the mouse parieto-frontal network
VL - 10
ER -
TY - JOUR
AB - Assemblies of colloidal semiconductor nanocrystals (NCs) in the form of thin solid films leverage the size-dependent quantum confinement properties and the wet chemical methods vital for the development of the emerging solution-processable electronics, photonics, and optoelectronics technologies. The ability to control the charge carrier transport in the colloidal NC assemblies is fundamental for altering their electronic and optical properties for the desired applications. Here we demonstrate a strategy to render the solids of narrow-bandgap NC assemblies exclusively electron-transporting by creating a type-II heterojunction via shelling. Electronic transport of molecularly cross-linked PbTe@PbS core@shell NC assemblies is measured using both a conventional solid gate transistor and an electric-double-layer transistor, as well as compared with those of core-only PbTe NCs. In contrast to the ambipolar characteristics demonstrated by many narrow-bandgap NCs, the core@shell NCs exhibit exclusive n-type transport, i.e., drastically suppressed contribution of holes to the overall transport. The PbS shell that forms a type-II heterojunction assists the selective carrier transport by heavy doping of electrons into the PbTe-core conduction level and simultaneously strongly localizes the holes within the NC core valence level. This strongly enhanced n-type transport makes these core@shell NCs suitable for applications where ambipolar characteristics should be actively suppressed, in particular, for thermoelectric and electron-transporting layers in photovoltaic devices.
AU - Miranti, Retno
AU - Shin, Daiki
AU - Septianto, Ricky Dwi
AU - Ibáñez, Maria
AU - Kovalenko, Maksym V.
AU - Matsushita, Nobuhiro
AU - Iwasa, Yoshihiro
AU - Bisri, Satria Zulkarnaen
ID - 7634
IS - 3
JF - ACS Nano
TI - Exclusive electron transport in Core@Shell PbTe@PbS colloidal semiconductor nanocrystal assemblies
VL - 14
ER -
TY - CONF
AB - Concurrent programming can be notoriously complex and error-prone. Programming bugs can arise from a variety of sources, such as operation re-reordering, or incomplete understanding of the memory model. A variety of formal and model checking methods have been developed to address this fundamental difficulty. While technically interesting, existing academic methods are still hard to apply to the large codebases typical of industrial deployments, which limits their practical impact.
AU - Koval, Nikita
AU - Sokolova, Mariia
AU - Fedorov, Alexander
AU - Alistarh, Dan-Adrian
AU - Tsitelov, Dmitry
ID - 7635
SN - 9781450368186
T2 - Proceedings of the ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming, PPOPP
TI - Testing concurrency on the JVM with Lincheck
ER -
TY - CONF
AB - Balanced search trees typically use key comparisons to guide their operations, and achieve logarithmic running time. By relying on numerical properties of the keys, interpolation search achieves lower search complexity and better performance. Although interpolation-based data structures were investigated in the past, their non-blocking concurrent variants have received very little attention so far.
In this paper, we propose the first non-blocking implementation of the classic interpolation search tree (IST) data structure. For arbitrary key distributions, the data structure ensures worst-case O(log n + p) amortized time for search, insertion and deletion traversals. When the input key distributions are smooth, lookups run in expected O(log log n + p) time, and insertion and deletion run in expected amortized O(log log n + p) time, where p is a bound on the number of threads. To improve the scalability of concurrent insertion and deletion, we propose a novel parallel rebuilding technique, which should be of independent interest.
We evaluate whether the theoretical improvements translate to practice by implementing the concurrent interpolation search tree, and benchmarking it on uniform and nonuniform key distributions, for dataset sizes in the millions to billions of keys. Relative to the state-of-the-art concurrent data structures, the concurrent interpolation search tree achieves performance improvements of up to 15% under high update rates, and of up to 50% under moderate update rates. Further, ISTs exhibit up to 2X less cache-misses, and consume 1.2 -- 2.6X less memory compared to the next best alternative on typical dataset sizes. We find that the results are surprisingly robust to distributional skew, which suggests that our data structure can be a promising alternative to classic concurrent search structures.
AU - Brown, Trevor A
AU - Prokopec, Aleksandar
AU - Alistarh, Dan-Adrian
ID - 7636
SN - 9781450368186
T2 - Proceedings of the ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming, PPOPP
TI - Non-blocking interpolation search trees with doubly-logarithmic running time
ER -
TY - JOUR
AB - The evolution of finitely many particles obeying Langevin dynamics is described by Dean–Kawasaki equations, a class of stochastic equations featuring a non-Lipschitz multiplicative noise in divergence form. We derive a regularised Dean–Kawasaki model based on second order Langevin dynamics by analysing a system of particles interacting via a pairwise potential. Key tools of our analysis are the propagation of chaos and Simon's compactness criterion. The model we obtain is a small-noise stochastic perturbation of the undamped McKean–Vlasov equation. We also provide a high-probability result for existence and uniqueness for our model.
AU - Cornalba, Federico
AU - Shardlow, Tony
AU - Zimmer, Johannes
ID - 7637
IS - 2
JF - Nonlinearity
SN - 09517715
TI - From weakly interacting particles to a regularised Dean-Kawasaki model
VL - 33
ER -
TY - JOUR
AB - Following on from our recent work, we investigate a stochastic approach to non-equilibrium quantum spin systems. We show how the method can be applied to a variety of physical observables and for different initial conditions. We provide exact formulae of broad applicability for the time-dependence of expectation values and correlation functions following a quantum quench in terms of averages over classical stochastic processes. We further explore the behavior of the classical stochastic variables in the presence of dynamical quantum phase transitions, including results for their distributions and correlation functions. We provide details on the numerical solution of the associated stochastic differential equations, and examine the growth of fluctuations in the classical description. We discuss the strengths and limitations of the current implementation of the stochastic approach and the potential for further development.
AU - De Nicola, Stefano
AU - Doyon, B.
AU - Bhaseen, M. J.
ID - 7638
IS - 1
JF - Journal of Statistical Mechanics: Theory and Experiment
TI - Non-equilibrium quantum spin dynamics from classical stochastic processes
VL - 2020
ER -
TY - JOUR
AU - Han, Huibin
AU - Rakusova, Hana
AU - Verstraeten, Inge
AU - Zhang, Yuzhou
AU - Friml, Jiří
ID - 7643
JF - Plant Physiology
SN - 0032-0889
TI - SCFTIR1/AFB auxin signaling for bending termination during shoot gravitropism
ER -
TY - JOUR
AB - In plant cells, environmental stressors promote changes in connectivity between the cortical ER and the PM. Although this process is tightly regulated in space and time, the molecular signals and structural components mediating these changes in inter-organelle communication are only starting to be characterized. In this report, we confirm the presence of a putative tethering complex containing the synaptotagmins 1 and 5 (SYT1 and SYT5) and the Ca2+ and lipid binding protein 1 (CLB1/SYT7). This complex is enriched at ER-PM contact sites (EPCS), have slow responses to changes in extracellular Ca2+, and display severe cytoskeleton-dependent rearrangements in response to the trivalent lanthanum (La3+) and gadolinium (Gd3+) rare earth elements (REEs). Although REEs are generally used as non-selective cation channel blockers at the PM, here we show that the slow internalization of REEs into the cytosol underlies the activation of the Ca2+/Calmodulin intracellular signaling, the accumulation of phosphatidylinositol-4-phosphate (PI4P) at the PM, and the cytoskeleton-dependent rearrangement of the SYT1/SYT5 EPCS complexes. We propose that the observed EPCS rearrangements act as a slow adaptive response to sustained stress conditions, and that this process involves the accumulation of stress-specific phosphoinositides species at the PM.
AU - Lee, E
AU - Vila Nova Santana, B
AU - Samuels, E
AU - Benitez-Fuente, F
AU - Corsi, E
AU - Botella, MA
AU - Perez-Sancho, J
AU - Vanneste, S
AU - Friml, Jiří
AU - Macho, A
AU - Alves Azevedo, A
AU - Rosado, A
ID - 7646
JF - Journal of Experimental Botany
SN - 0022-0957
TI - Rare earth elements induce cytoskeleton-dependent and PI4P-associated rearrangement of SYT1/SYT5 ER-PM contact site complexes in Arabidopsis
ER -
TY - JOUR
AB - We consider a dilute, homogeneous Bose gas at positive temperature. The system is investigated in the Gross–Pitaevskii limit, where the scattering length a is so small that the interaction energy is of the same order of magnitude as the spectral gap of the Laplacian, and for temperatures that are comparable to the critical temperature of the ideal gas. We show that the difference between the specific free energy of the interacting system and the one of the ideal gas is to leading order given by 4πa(2ϱ2−ϱ20). Here ϱ denotes the density of the system and ϱ0 is the expected condensate density of the ideal gas. Additionally, we show that the one-particle density matrix of any approximate minimizer of the Gibbs free energy functional is to leading order given by the one of the ideal gas. This in particular proves Bose–Einstein condensation with critical temperature given by the one of the ideal gas to leading order. One key ingredient of our proof is a novel use of the Gibbs variational principle that goes hand in hand with the c-number substitution.
AU - Deuchert, Andreas
AU - Seiringer, Robert
ID - 7650
IS - 6
JF - Archive for Rational Mechanics and Analysis
SN - 0003-9527
TI - Gross-Pitaevskii limit of a homogeneous Bose gas at positive temperature
VL - 236
ER -