IA Scholar Query: Relaxed matching for stabilization of relative equilibria of mechanical systems.
https://scholar.archive.org/
Internet Archive Scholar query results feedeninfo@archive.orgMon, 21 Nov 2022 00:00:00 GMTfatcat-scholarhttps://scholar.archive.org/help1440Parameterised-Response Zero-Intelligence Traders
https://scholar.archive.org/work/ste777tgdzgs7flv4o7e2qqjxe
I introduce PRZI (Parameterised-Response Zero Intelligence), a new form of zero-intelligence trader intended for use in simulation studies of the dynamics of continuous double auction markets. Like Gode & Sunder's classic ZIC trader, PRZI generates quote-prices from a random distribution over some specified domain of allowable quote-prices. Unlike ZIC, which uses a uniform distribution to generate prices, the probability distribution in a PRZI trader is parameterised in such a way that its probability mass function (PMF) is determined by a real-valued control variable s in the range [-1.0, +1.0] that determines the _strategy_ for that trader. When s=0, a PRZI trader is identical to ZIC, with a uniform PMF; but when |s|=~1 the PRZI trader's PMF becomes maximally skewed to one extreme or the other of the price-range, thereby making its quote-prices more or less urgent, biasing the quote-price distribution toward or away from the trader's limit-price. To explore the co-evolutionary dynamics of populations of PRZI traders that dynamically adapt their strategies, I show results from long-term market experiments in which each trader uses a simple stochastic hill-climber algorithm to repeatedly evaluate alternative s-values and choose the most profitable at any given time. In these experiments the profitability of any particular s-value may be non-stationary because the profitability of one trader's strategy at any one time can depend on the mix of strategies being played by the other traders at that time, which are each themselves continuously adapting. Results from these market experiments demonstrate that the population of traders' strategies can exhibit rich dynamics, with periods of stability lasting over hundreds of thousands of trader interactions interspersed by occasional periods of change. Python source-code for the work reported here has been made publicly available on GitHub.Dave Cliffwork_ste777tgdzgs7flv4o7e2qqjxeMon, 21 Nov 2022 00:00:00 GMTChemical vapor deposition, characterization, and thermodynamic phase diagram calculations of sp2-boron nitride thin films
https://scholar.archive.org/work/lrl7osi5a5cklblcxqaz7i6f3m
The objectives of the research presented in this Thesis have been to (1) advance the field of homo- and heteroepitaxial growth of sp2-hybridized boron nitride (sp2-BN) thin films via chemical vapor deposition (CVD) and (2) evaluate the usefulness of utilizing calculated equilibrium phase diagrams for the prediction of sp2-BN phases - namely hexagonal BN (h-BN) and rhombohedral BN (r-BN) – prepared by thermal CVD. The deposited sp2-BN thin films related to objective (1) were characterized to determine the effects of implemented CVD growth parameters on film growth rates, the substrate-film interfacial microstructure, bulk film microstructure and crystallinity, chemical composition and bonding characteristics, and surface morphology and roughness. The calculated equilibrium phase diagrams related to objective (2) were compared with sp2-BN CVD processes from experimental literature to determine favorable thermodynamic conditions for the deposition of sp2-BN and to discover discrepancies related to the kinetics of CVD growth and sp2-BN phase transformations. The first project related to the achievement of objective (1) of this Thesis was the growth of nanocrystalline sp2-BN thin films on (0001) 4H-SiC substrates at 1030 oC via continuous flow and discontinuous flow-modulated CVD techniques using diborane (B2H6) and ammonia (NH3) as the B- and N sources, respectively. The latter technique enabled observations of both the effect of hydrogen purge steps between precursor injections and the length of injection times for B2H6 on the stoichiometry and microstructure of the films. Stoichiometric BN was achieved in all films grown continuously within the N/B gas phase ratio range of 20 – 200; this was not observed for the discontinuously grown films unless both the B2H6 flow rate and the injection time were minimized. Cross-section transmission electro [...]Philip Jean-remywork_lrl7osi5a5cklblcxqaz7i6f3mThu, 17 Nov 2022 00:00:00 GMTRare-earth based tetrapyrrolic sandwiches: chemistry, materials and applications
https://scholar.archive.org/work/jje4afudivfifpj4f6aga26744
This review summarises advances in chemistry of tetrapyrrole sandwiches with rare earth elements and highlights the current state of their use in single-molecule magnetism, organic field-effect transistors, conducting materials and nonlinear optics.Alexander G. Martynov, Yoji Horii, Keiichi Katoh, Yongzhong Bian, Jianzhuang Jiang, Masahiro Yamashita, Yulia G. Gorbunovawork_jje4afudivfifpj4f6aga26744Mon, 14 Nov 2022 00:00:00 GMTCollective models and the marriage market
https://scholar.archive.org/work/ymeaor35yrhhjpti6mwzs2kcwi
In this paper, I develop an integrated approach to collective models and matching models of the marriage market. In the collective framework, both household formation and the intra-household allocation of bargaining power are taken as given. This is no longer the case in the present contribution, where both are endogenous to the determination of equilibrium on the marriage market. I characterize a class of "proper" collective models which can be embedded into a general matching framework with imperfectly transferable utility. In such models, the bargaining sets are parametrized by an analytical device called distance function, which plays a key role both for writing down the usual stability conditions and for estimation. In general, however, distance functions are not known in closed-form. I provide an efficient method for computing distance functions, that works even with the most complex collective models. Finally, I provide a fully-fledged application using PSID data. I identify the sharing rule and its distribution and study the evolution of the sharing rule and housework time sharing in the United States since 1969. In a counterfactual experiment, I simulate the impact of closing the gender wage gap.Simon Weberwork_ymeaor35yrhhjpti6mwzs2kcwiMon, 14 Nov 2022 00:00:00 GMTOrbital Stabilization of Point-to-Point Maneuvers in Underactuated Mechanical Systems
https://scholar.archive.org/work/bo6bid5ad5eirorvyrkgwmwkxm
The task of inducing, via continuous static state-feedback control, an asymptotically stable heteroclinic orbit in a nonlinear control system is considered in this paper. The main motivation comes from the problem of ensuring convergence to a so-called point-to-point maneuver in an underactuated mechanical system. Namely, to a smooth curve in its state--control space, which is consistent with the system dynamics and connects two (linearly) stabilizable equilibrium points. The proposed method uses a particular parameterization, together with a state projection onto the maneuver as to combine two linearization techniques for this purpose: the Jacobian linearization at the equilibria on the boundaries and a transverse linearization along the orbit. This allows for the computation of stabilizing control gains offline by solving a semidefinite programming problem. The resulting nonlinear controller, which simultaneously asymptotically stabilizes both the orbit and the final equilibrium, is time-invariant, locally Lipschitz continuous, requires no switching, and has a familiar feedforward plus feedback--like structure. The method is also complemented by synchronization function--based arguments for planning such maneuvers for mechanical systems with one degree of underactuation. Numerical simulations of the non-prehensile manipulation task of a ball rolling between two points upon the "butterfly" robot demonstrates the efficacy of the synthesis.Christian Fredrik Sætre, Anton S. Shiriaevwork_bo6bid5ad5eirorvyrkgwmwkxmMon, 14 Nov 2022 00:00:00 GMTHeterojunctions fabricated by surface activated bonding–dependence of their nanostructural and electrical characteristics on thermal process
https://scholar.archive.org/work/qy5esrhprbc3bco3ls4xk455v4
Recent achievements in the research of heterojunctions fabricated using surface activated bonding (SAB), one of the practically useful direct wafer bonding technologies, are discussed. The response of bonding interfaces to post-bonding annealing is focused. These junctions reveal high thermal tolerance (1000 °C in the case of junctions made of widegap materials) despite differences in coefficients of thermal expansion between bonded materials. Defect layers with several nm thickness formed by the surface activation process at the as-bonded interfaces get faint and their electrical and mechanical properties are improved by annealing. These results show that as-bonded interfaces are in a metastable state, and novel functional devices are likely to be realized by applying wafer processing steps to SAB-based junctions. Characteristics of III–V//Si multijunction solar cells, GaN-on-diamond high electron mobility transistors, and metal-foil based low-loss interconnects that are fabricated by processing SAB-based junctions are described, and future prospects are presented.Naoteru Shigekawa, Jianbo Liang, Yutaka Ohnowork_qy5esrhprbc3bco3ls4xk455v4Mon, 14 Nov 2022 00:00:00 GMTDiscrete Geometric Singular Perturbation Theory
https://scholar.archive.org/work/4joa25wuyzdulhoa5q23sufecm
We propose a mathematical formalism for discrete multi-scale dynamical systems induced by maps which parallels the established geometric singular perturbation theory for continuous-time fast-slow systems. We identify limiting maps corresponding to both 'fast' and 'slow' iteration under the map. A notion of normal hyperbolicity is defined by a spectral gap requirement for the multipliers of the fast limiting map along a critical fixed-point manifold S. We provide a set of Fenichel-like perturbation theorems by reformulating pre-existing results so that they apply near compact, normally hyperbolic submanifolds of S. The persistence of the critical manifold S, local stable/unstable manifolds W^s/u_loc(S) and foliations of W^s/u_loc(S) by stable/unstable fibers is described in detail. The practical utility of the resulting discrete geometric singular perturbation theory (DGSPT) is demonstrated in applications. First, we use DGSPT to identify singular geometry corresponding to excitability, relaxation, chaotic and non-chaotic bursting in a map-based neural model. Second, we derive results which relate the geometry and dynamics of fast-slow ODEs with non-trivial time-scale separation and their Euler-discretized counterpart. Finally, we show that fast-slow ODE systems with fast rotation give rise to fast-slow Poincaré maps, the geometry and dynamics of which can be described in detail using DGSPT.Samuel Jelbart, Christian Kuehnwork_4joa25wuyzdulhoa5q23sufecmTue, 08 Nov 2022 00:00:00 GMTTwo-Step Estimation of a Strategic Network Formation Model with Clustering
https://scholar.archive.org/work/w666iavowfhnbesrttnqvhez2y
This paper explores strategic network formation under incomplete information using data from a single large network. We allow the utility function to be nonseparable in an individual's link choices to capture the spillover effects from friends in common. In a network with n individuals, the nonseparable utility drives an individual to choose between 2^n-1 overlapping portfolios of links. We develop a novel approach that applies the Legendre transform to the utility function so that the optimal decision of an individual can be represented as a sequence of correlated binary choices. The link dependence that results from the preference for friends in common is captured by an auxiliary variable introduced by the Legendre transform. We propose a two-step estimator that is consistent and asymptotically normal. We also derive a limiting approximation of the game as n grows large that can help simplify the computation in very large networks. We apply these methods to favor exchange networks in rural India and find that the direction of support from a mutual link matters in facilitating favor provision.Geert Ridder, Shuyang Shengwork_w666iavowfhnbesrttnqvhez2yTue, 08 Nov 2022 00:00:00 GMTPlanet-Disk Interactions
https://scholar.archive.org/work/owrb5g2xvvgzbdfv7cesk6eppy
Planet-disk interactions, where an embedded massive body interacts gravitationally with the protoplanetary disk it was formed in, can play an important role in reshaping both the disk and the orbit of the planet. Spiral density waves are launched into the disk by the planet, which, if they are strong enough, can lead to the formation of a gap. Both effects are observable with current instruments. The back-reaction of perturbations induced in the disk, both wave-like and non-wavelike, is a change in orbital elements of the planet. The efficiency of orbital migration is a long-standing problem in planet formation theory. We discuss recent progress in planet-disk interactions for different planet masses and disk parameters, in particular the level of turbulence, and progress in modeling observational signatures of embedded planets.Sijme-Jan Paardekooper, Ruobing Dong, Paul Duffell, Jeffrey Fung, Frederic S. Masset, Gordon Ogilvie, Hidekazu Tanakawork_owrb5g2xvvgzbdfv7cesk6eppyTue, 08 Nov 2022 00:00:00 GMTPotential of metal–organic frameworks for adsorptive separation of industrially and environmentally relevant liquid mixtures
https://scholar.archive.org/work/arhf7q27rbfjflbxd7rdilh3t4
Metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) are defined as crystalline, open,coordination network architectures with potential voids. They have drawn momentous attention across several crossroads of material chemistry since their discovery, owing to an exciting plethora of application-oriented footprints left by this class of crystalline, supramolecular and open coordination architectures. The unmatched aspect of tunable coordination nanospace arising from the countless choice of pre-functionalized organic struts pertaining to varying lengths alongside multivariate coordination geometries/oxidation states of the metal nodes, bestows a distinct chemical tailorability facet to this class of porous materials. Amidst the two-decade long attention dedicated to the adsorption-governed purification of gases, the MOF literature has substantially expanded its horizon into the manifestation of industrially relevant liquid mixtures' adsorptive separation-driven purification. Such chemical separation phenomena categorically encompasses high importance to the manufacturing and processing industry sectors, apart from the fundamental scientific pursuit of discovering novel physicochemical principles. Aimed at the energy-economic preparation of pure industrial feedstocks and their consequent usage as end products, structure-property correlations pursued in the alleys of coordination chemistry has led to major advancements in a number of critical separation frontiers, inclusive of biofuels (alcohol/water), diverse hydrocarbon mixtures, and chiral species. This comprehensive review summarizes the topical developments accrued in the field of MOF-based liquid mixtures' adsorptive separation phenomena, structure-selectivity relationships as well as the associated plausible mechanisms substantiating such behavior.Soumya Mukherjee, Aamod V. Desai, Sujit K. Ghoshwork_arhf7q27rbfjflbxd7rdilh3t4Mon, 07 Nov 2022 00:00:00 GMTNdBaInO4 based triple (electronic, ionic and protonic) conductor for solid oxide fuel cell applications
https://scholar.archive.org/work/5wjpqdmzdng7xpuchinkyo2zfu
Oxide-ion conducting materials have never failed to attract intensive attention due to their potential to be used for the applications of solid oxide fuel cell (SOFC) devices. With the aim of reducing the operating temperatures of SOFC devices to the intermediate high temperature range (500oC-800 oC), the design and synthesis of a new structure family to be used as the electrolyte material could be crucial. In this thesis, the potential of calcium-doped layered perovskite compounds, BaNd1-xCaxInO4-x/2 (where x is the Ca content), as protonic conductors was experimentally investigated. The single phase of monoclinic crystal structure with the P21/c symmetry was confirmed in the as-synthesized BaNd1-xCaxInO4-x/2 solid solutions by XRD characterisations. The acceptor-doped ceramics exhibited improved total conductivities that were 1-2 orders of magnitude higher than those of the parent material, BaNdInO4. The highest total conductivity of 2.6 x 10-3 Scm-1 was obtained for the BaNd0.8Ca0.2InO3.90 sample at a temperature of 750 oC in air. Electrochemical impedance spectroscopy measurements of the x = 0.1 and x = 0.2 substituted samples showed higher total conductivity under humid environments than those measured in a dry environment over a large temperature range (250 oC-750 oC). At 500 oC, the total conductivity of the 20% substituted sample in humid air (~3% H2O) was 1.3 x 10-4 Scm-1. The incorporation of water vapour decreased the activation energies of the bulk conductivity of the BaNd0.8Ca0.2InO3.90 sample from 0.755(2) eV to 0.678(2) eV in air. The saturated BaNd0.8Ca0.2InO3.90 sample contained 2.2 mol% protonic defects, which caused an expansion in the lattice according to the in-situ X-ray diffraction data. Combining studies of the impedance behaviour with 4-probe DC conductivity measurements obtained in humid air which showed a decrease in the resistance of the x=0.2 sample, it could be concluded that experimental evidence indicates that BaNd1-xCaxInO4-x/2 exhibits triple (oxygen-ion, proton and hole) conduct [...]Yu Zhou, Stephen Skinner, China Scholarship Councilwork_5wjpqdmzdng7xpuchinkyo2zfuMon, 07 Nov 2022 00:00:00 GMTUltrafast carrier and quasiparticle dynamics in strongly confined perovskite nanoplatelets
https://scholar.archive.org/work/wo7kjgfzjzcwlgpzp5mckqjqcm
Over the past decade, lead halide perovskites (LHPs) have received considerable attention thanks to their impressive optoelectronic properties. Today, LHP-based devices are one of the most efficient singlejunction solar cells, with power-conversion efficiencies reaching 25.7%. Likewise, nanostructures of the same material have emerged with tremendous potential for light-emitting and lasing applications. The perovskite complex and dynamic structures also makes them fascinating for fundamental photophysical studies, not only to apply in the context of the device improvements but also for a much broader class of semiconductors. Typically, charge carrier dynamics on the ultrafast timescale, from a few nanoseconds down to tens of femtoseconds, are monitored by time-resolved spectroscopic techniques using ultrashort laser pulses. The aim of this work is to associate transient absorption (TA) and time-resolved photoluminescence (TRPL) spectroscopy for investigating early photophysical mechanisms in low-dimensional perovskite nanocrystals (PNCs). While most available TRPL experimental techniques are limited by a temporal resolution of a few picoseconds, broadband fluorescence upconversion spectroscopy (FLUPS) is employed to obtain two-dimensional spectro-temporal data with a sub-picosecond temporal resolution. Chapters 1 and 2 provide the scientific background relevant to the thesis. Chapter 1 establishes the fundamental photophysical concepts for bulk and confined semiconductors and provides a general overview of the PNC optoelectronic properties, reviewing the relevant literature. The second chapter focuses on TRPL spectroscopy and details the theoretical and experimental approaches for FLUPS, the primary technique employed in this work. Chapter 3 describes the synthetic procedure to obtain colloidal blue-emitting CsPbBr 3 nanoplatelets (NPls). The product is then characterized by standard methods, including transmission electron microscopy, cyclic voltammetry and linear UV-Vis absorption and emission spectroscopy. The consequences of strong quantum and dielectric confinements are highlighted and induce unique optoelectronic properties. The importance of capping ligands engineering for passivating the perovskite surface states is also stressed. Capping ligands can also increase the NPl emission efficiency and long-term stability. Chapters 4 and 5 discuss the charge carrier dynamics under weak and strong excitation regimes. By 5 combining FLUPS and TA data, complex photophysical behaviors within the first ten picoseconds are revealed. Under low excitation intensities, the NPl dynamics are dominated by an ensemble of independent excitons. Besides, at high pump fluences, enhanced carrier-carrier interactions induce surprisingly stable and emissive exciton-exciton pairs, also called biexcitons. The properties and recombination mechanisms of the biexcitons display typical quantum well signatures. Finally, chapter 6 investigates the charge separation and subsequent charge recombination mechanisms in CsPbBr 3 NPls combining FLUPS, TA and nanosecond flash photolysis measurements. NPl-acceptor complexes are synthesized by attaching phenothiazine and p-benzoquinone to the NPl surface, acting as hole and electron acceptors, respectively. Excitation energy-dependent FLUPS measurements are carried out to unveil fast interfacial charge transfer from the perovskite band edge and ultrafast hot carrier transfer from higher energy levels.Etienne Christophe Sociework_wo7kjgfzjzcwlgpzp5mckqjqcmMon, 07 Nov 2022 00:00:00 GMTA coupled ice sheet model for the Global Resolved Energy Balance model for global simulations on time-scales of 100 kyr
https://scholar.archive.org/work/7laccaqspfctzet6yoa6wqxtme
We developed a new global ice sheet model for simple climate model the Global Resolved Energy Balance (GREB) in the project for paleoclimate simulation. In the thesis, we described how the ISM was built and how climate and ice sheet components coupled to have globally coupled Earth system model - the GREB-ISM. After that, a series of benchmark experiments are presented to evaluate the performance of the GREB-ISM in long-term mean state and transition simulations. Last but not least, we applied the GREB-ISM to understand the importance and relevant physics of climate-ice sheet feedback by using a series of sensitivity experiments.Zhiang Xiework_7laccaqspfctzet6yoa6wqxtmeThu, 03 Nov 2022 00:00:00 GMTNumerical schemes for a multi-species BGK model with velocity-dependent collision frequency
https://scholar.archive.org/work/4jyhsw4debdonpop76kc6mbaoe
We consider a kinetic description of a multi-species gas mixture modeled with Bhatnagar-Gross-Krook (BGK) collision operators, in which the collision frequency varies not only in time and space but also with the microscopic velocity. In this model, the Maxwellians typically used in standard BGK operators are replaced by a generalization of such target functions, which are defined by a variational procedure . In this paper we present a numerical method for simulating this model, which uses an Implicit-Explicit (IMEX) scheme to minimize a certain potential function, mimicking the Lagrange functional that appears in the theoretical derivation. We show that theoretical properties such as conservation of mass, total momentum and total energy as well as positivity of the distribution functions are preserved by the numerical method, and illustrate its usefulness and effectiveness with numerical examples.Jeffrey Haack, Cory Hauck, Christian Klingenberg, Marlies Pirner, Sandra Warneckework_4jyhsw4debdonpop76kc6mbaoeThu, 03 Nov 2022 00:00:00 GMTMagnetically Dominated Disks in Tidal Disruption Events and Quasi-Periodic Eruptions
https://scholar.archive.org/work/54kc6svdcvgfbbh7d2ktwl22fq
The classical radiation pressure instability has been a persistent theoretical feature of thin, radiatively efficient accretion disks with accretion rates 1 to 100 per cent of the Eddington rate. But there is only limited evidence of its occurrence in nature: rapid heartbeat oscillations of a few X-ray binaries and now, perhaps, the new class of hourly X-ray transients called quasi-periodic eruptions (QPEs). The accretion disks formed in tidal disruption events (TDEs) have been observed to peacefully trespass through the range of unstable accretion rates without exhibiting any clear sign of the instability. We try to explain the occurrence or otherwise of this instability in these systems, by constructing steady state 1D models of thin magnetic accretion disks. The local magnetic pressure in the disk is assumed to be dominated by toroidal fields arising from a dynamo sourced by magneto-rotational instability (MRI). We choose a physically motivated criterion of MRI saturation, validated by recent magnetohydrodynamic simulations, to determine the strength of magnetic pressure in the disk. The resulting magnetic pressure support efficiently shrinks: (1) the parameter space of unstable mass accretion rates, explaining the absence of instability in systems such as TDEs and (2) the range of unstable radii in the inner accretion disk, which can shorten the quasi-periods of instability limit-cycles by more than three orders of magnitude, explaining the observed periods ( a few hrs) of QPEs. In addition to examining stability properties of strongly magnetized disks, we predict other observational signatures such as spectral hardening factors and jet luminosities to test the compatibility of our disk models with observations of apparently stable TDE disks.Karamveer Kaur, Nicholas C. Stone, Shmuel Gilbaumwork_54kc6svdcvgfbbh7d2ktwl22fqTue, 01 Nov 2022 00:00:00 GMTPairing cellular and synaptic dynamics into building blocks of rhythmic neural circuits
https://scholar.archive.org/work/mc2bzfpdfbc5rcyyevvigt465m
The purpose of this paper is trifold -- to serve as an instructive resource and a reference catalog for biologically plausible modeling with i) conductance-based models, coupled with ii) strength-varying slow synapse models, culminating in iii) two canonical pair-wise rhythm-generating networks. We document the properties of basic network components: cell models and synaptic models, which are prerequisites for proper network assembly. Using the slow-fast decomposition we present a detailed analysis of the cellular dynamics including a discussion of the most relevant bifurcations. Several approaches to model synaptic coupling are also discussed, and a new logistic model of slow synapses is introduced. Finally, we describe and examine two types of bicellular rhythm-generating networks: i) half-center oscillators ii) excitatory-inhibitory pairs and elucidate a key principle -- the network hysteresis underlying the stable onset of emergent slow bursting in these neural building blocks. These two cell networks are a basis for more complicated neural circuits of rhythmogensis and feature in our models of swim central pattern generators.James Scully, Jassem Bourahmah, David Bloom, Andrey L Shilnikovwork_mc2bzfpdfbc5rcyyevvigt465mTue, 01 Nov 2022 00:00:00 GMTThe effects of foraging behaviour on food-web structure and dynamics
https://scholar.archive.org/work/z7qh32ops5e3tmuaaumnmn5hei
A food web summarises the foraging relationships among creatures within a community. Therefore, to understand how food-web structural and dynamical properties emerge, it is essential to clarify how foraging behaviour (as the underpinning driver) shapes the properties at the level of the whole food web. In this thesis, we examine the influence of several behavioural aspects of foraging on food webs, as well as the mechanisms that cause these influences. In Chapter 2, by conducting food-web dynamical modelling that is constrained by species' metabolism (following Metabolic Theory of Ecology, MTE), we bring to light how the foraging strategy and dimensionality interact with food-web structures to determine species coexistence in food webs. In Chapter 3, by further introducing Optimal Foraging Theory (OFT) as a diet choice mechanism, we explore the food-web structural and dynamical consequences when species are able to adjust their diet depending on resource abundances. We show that incorporating OFT indeed significantly affect both the structure and the dynamics of food webs, while the impacts can be varied and dependent on parameters that control the properties of both the community and its species' behaviour. We then proceed in Chapter 4, by modelling using the same MTEOFT framework, to investigate the emergent food-web structure under conditions where species cannot fully comply with OFT but rather are constrained by the predation risk they undertake. We develop a new model that describes consumers' diet choice under this predation-risk effect, and find that we can capture better the empirical food-web structure than can the classical OFT model without predation-risk considerations. By showing how foraging strategy and dimensionality, adaptive diet choice, and predation risk-driven response scale up their effect to determine food-web properties, overall, the findings of this thesis shed light on how food-web properties emerge from organismal foraging behaviour. Also, the present thesis lays a firm quantitative fo [...]Hsi-Cheng Ho, Samraat Pawar, Jason Tylianakis, Imperial College Londonwork_z7qh32ops5e3tmuaaumnmn5heiTue, 01 Nov 2022 00:00:00 GMTPairing cellular and synaptic dynamics into building blocks of rhythmic neural circuits
https://scholar.archive.org/work/l7ovglesbnbxvnbkn6bwhomyp4
The purpose of this paper is to serve as an instructive resource and a reference catalog for biologically plausible modeling with i) conductance-based models, coupled with ii) strength varying slow synapse models, culminating in iii) two canonical pair-wise rhythm-generating networks. We document the properties of basic network components: cell models and synaptic models, which are prerequisites for proper network assembly. Using the slow-fast decomposition we present a detailed analysis of the cellular dynamics including a discussion of the most relevant bifurcations. Several approaches to model synaptic coupling are also discussed, and a new logistic model of slow synapses is introduced. Finally, we describe and examine two types of bicellular rhythm-generating networks: i) half center oscillators ii) excitatory-inhibitory pairs and elucidate a key principle - the network hysteresis underlying the stable onset of emergent slow bursting in these neural building blocks. These two cell networks are a basis for more complicated neural circuits of rhythmogenesis and feature in our models of swim central pattern generators.James Scully, Jassem Bourahmah, David Bloom, Andrey Shilnikovwork_l7ovglesbnbxvnbkn6bwhomyp4Tue, 01 Nov 2022 00:00:00 GMTSaddle-Type Blow-Up Solutions with Computer-Assisted Proofs: Validation and Extraction of Global Nature
https://scholar.archive.org/work/yji7y2hc5vfi5h7v7sb74fb4zm
In this paper, blow-up solutions of autonomous ordinary differential equations (ODEs) which are unstable under perturbations of initial points, referred to as saddle-type blow-up solutions, are studied. Combining dynamical systems machinery (e.g., compactifications, time-scale desingularizations of vector fields) with tools from computer-assisted proofs (e.g., rigorous integrators, the parameterization method for invariant manifolds), these blow-up solutions are obtained as trajectories on local stable manifolds of hyperbolic saddle equilibria at infinity. With the help of computer-assisted proofs, global trajectories on stable manifolds, inducing blow-up solutions, provide a global picture organized by global-in-time solutions and blow-up solutions simultaneously. Using the proposed methodology, intrinsic features of saddle-type blow-ups are observed: locally smooth dependence of blow-up times on initial points, level set distribution of blow-up times, and decomposition of the phase space playing a role as separatrixes among solutions, where the magnitude of initial points near those blow-ups does not matter for asymptotic behavior. Finally, singular behavior of blow-up times on initial points belonging to different family of blow-up solutions is addressed.Jean-Philippe Lessard, Kaname Matsue, Akitoshi Takayasuwork_yji7y2hc5vfi5h7v7sb74fb4zmSun, 30 Oct 2022 00:00:00 GMTAdvances in honeycomb layered oxides: Part II – Theoretical advances in the characterisation of honeycomb layered oxides with optimised lattices of cations
https://scholar.archive.org/work/dknl5fqwxzcv3l3n4f5xuk2roa
The quest for a successful condensed matter theory that incorporates diffusion of cations, whose trajectories are restricted to a honeycomb/hexagonal pattern prevalent in honeycomb layered materials is ongoing, with the recent progress discussed herein focusing on symmetries, topological aspects and phase transition descriptions of the theory. Such a theory is expected to differ both qualitatively and quantitatively from 2D electron theory on static carbon lattices, by virtue of the dynamical nature of diffusing cations within lattices in honeycomb layered materials. Herein, we have focused on recent theoretical progress in the characterisation of pnictogen- and chalcogen-based honeycomb layered oxides with emphasis on hexagonal/honeycomb lattices of cations. Particularly, we discuss the link between Liouville conformal field theory to expected experimental results characterising the optimal nature of the honeycomb/hexagonal lattices in congruent sphere packing problems. The diffusion and topological aspects are captured by an idealised model, which successfully incorporates the duality between the theory of cations and their vacancies. Moreover, the rather intriguing experimental result that a wide class of silver-based layered materials form stable Ag bilayers, each comprising a pair of triangular sub-lattices, suggests a bifurcation mechanism for the Ag triangular sub-lattices, which ultimately requires conformal symmetry breaking within the context of the idealised model, resulting in a cation monolayer-bilayer phase transition. Other relevant experimental, theoretical and computational techniques applicable to the characterisation of honeycomb layered materials have been availed for completeness.Godwill Mbiti Kanyolo, Titus Masesework_dknl5fqwxzcv3l3n4f5xuk2roaFri, 28 Oct 2022 00:00:00 GMT