A5089764617- Ecosystem dynamics and resilience
- Nonlinear Dynamics and Pattern Formation
- Ecology and Vegetation Dynamics Studies
- stochastic dynamics and bifurcation
- Land Use and Ecosystem Services
- Innovative Teaching Methods
- Astrophysical Phenomena and Observations
- Science Education and Pedagogy
- Gene Regulatory Network Analysis
- Innovative Teaching and Learning Methods
- Chaos control and synchronization
- Photosynthetic Processes and Mechanisms
- Earth Systems and Cosmic Evolution
- Laser Design and Applications
- Experimental Learning in Engineering
- Astrophysics and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- 3D Modeling in Geospatial Applications
- Peatlands and Wetlands Ecology
- Soil erosion and sediment transport
- Botany and Plant Ecology Studies
- Animal Ecology and Behavior Studies
- Interdisciplinary Research and Collaboration
- Soil Mechanics and Vehicle Dynamics
Virginia Commonwealth University
2020-2025
The Ohio State University
2018-2019
University of California, Berkeley
2011-2018
Compass (United States)
2018
University of Chile
2017
Durham University
2014
Cornell University
2005
Many ecosystems show both self-organized spatial patterns and multistability of possible states. The combination these two phenomena in different forms has a significant impact on the behavior changing environments. One notable case is connected to tristability distinct uniform states together with patterned states, which recently been found model studies dryland ecosystems. Using simple model, we determine extent parameter space, explore its effects system dynamics, consider implications...
Banded patterns consisting of alternating bare soil and dense vegetation have been observed in water-limited ecosystems across the globe, often appearing along gently sloped terrain with stripes aligned transverse to elevation gradient. In many cases, these bands are arced, field observations suggesting a link between orientation arcing relative grade curvature underlying terrain. We modify water transport Klausmeier model water–biomass interactions, originally posed on uniform hillslope,...
In many drylands around the globe, vegetation self-organizes into regular spatial patterns in response to aridity stress. We consider regularly-spaced bands, on gentle hill-slopes, that survive low rainfall conditions by harvesting additional stormwater from upslope low-infiltration bare zones. are interested robustness of this pattern formation survival mechanism changes variability. For this, we use a flow-kick modeling framework treats storms as instantaneous kicks soil water. The...
Spatially localized structures in the one-dimensional Gray–Scott reaction–diffusion model are studied using a combination of numerical continuation techniques and weakly nonlinear theory, focusing on regime which activator substrate diffusivities different but comparable. Localized states arise three ways: subcritical Turing instability present this regime, from folds branch spatially periodic states. They also fold uniform These solution branches interconnect complex ways. We use to explore...
The theory of stationary spatially localized patterns in dissipative systems driven by time-independent forcing is well developed. With time-periodic forcing, related but time-dependent structures may result. These consist breathing patterns, or states that grow for part the cycle via nucleation new wavelengths pattern followed wavelength annihilation during remainder cycle. two competing processes lead to a complex phase diagram whose structure consequence series resonances between time and...
We develop a model for investigating the impact of rainstorm variability on formation banded vegetation patterns in dryland ecosystems. Water input, during rare rainstorms, is modeled as an instantaneous kick to soil water. The redistribution, from surface water moisture, accounts infiltration rate and downslope overland flow speed. These two positive feedbacks between biomass distributions act fast timescales rain storms. During dry periods, classic reaction-diffusion framework used slow...
We have designed an introductory laboratory course that engaged first-year undergraduate students in two complementary types of iteration: (1) iterative improvement experiments through cycles modeling systems, designing experiments, analyzing data, and refining models designs; (2) self reflecting on progress, soliciting feedback, implementing changes to study habits mind. The consisted three major activities: a thermal expansion activity, which spanned the first half semester; final research...
We report on an experimental, theoretical and numerical study of slanted snaking spatially localized parametrically excited waves the surface a water-surfactant mixture in Hele-Shaw cell. demonstrate experimentally presence hysteretic transition to extended when acceleration amplitude is varied, as well exhibiting snaking. The latter extend outside hysteresis loop. attribute this behavior conserved quantity, liquid volume, introduce universal model based symmetry arguments, which couples...
The Adler equation with time-periodic frequency modulation is studied. A series of resonances between the period and time scale for generation a phase slip identified. resulting parameter space structure determined using combination numerical continuation, simulations, asymptotic methods. Regions an integer number slips per are separated by regions noninteger numbers include canard trajectories that drift along unstable equilibria. Both high- low-frequency considered. An adiabatic...
Virtually all forms of life, from single-cell eukaryotes to complex, highly differentiated multicellular organisms, exhibit a property referred as symmetry. However, precise measures symmetry are often difficult formulate and apply in meaningful way biological systems, where symmetries asymmetries can be dynamic transient, or visually apparent but not reliably quantifiable using standard mathematics physics. Here, we present illustrate novel measure that draws on concepts information theory...
A longitudinally and transversely coherent, high repetition rate x-ray source with widely tunable wavelength is desired for a variety of experimental applications. free electron laser (FEL) powered by an beam from superconducting linac can reach the peak average power levels transverse coherence. However, generating coherent pulses significant challenge, especially at rate. This paper presents one-dimensional theoretical numerical investigation method to achieve longitudinal coherence...
Center manifold reduction is a standard technique in bifurcation theory, reducing the essential features of local bifurcations to equations small number variables corresponding critical eigenvalues. This method can be applied admissible differential for network, but it bears no obvious relation network structure. A fully inhomogeneous one which all nodes and couplings different. For this class networks, there are general circumstances center reduced inherit structure their own. arises by...
The generalized Swift--Hohenberg equation with a quadratic-cubic nonlinearity is used to study the persistence and decay of localized patterns in presence time-periodic parametric forcing. A novel resonance phenomenon between forcing period time required nucleate one wavelength pattern outside pinning region identified. generates distinct regions parameter space characterized by net number wavelengths gained or lost cycle. These are well described an asymptotic theory based on...
The broad energy range spanned by ASTRO-H instruments, from ~0.3 to 600 keV, with its high spectral resolution calorimeter and sensitive hard X-ray imaging, offers unique opportunities study black holes their environments. ability measure polarization is particularly novel, potential sources including blazars, Galactic pulsars binaries. In this White Paper, we present an overview of the synergistic instrumental capabilities improvements over prior missions. We also show how fits into...
We describe a simple experiment for measuring the thermal expansion coefficient of metal wire and discuss how can be used as tool exploring interplay measurement uncertainty scientific models. In particular, we probe regimes applicability three models wire: stiff massless, elastic massive. Using both analytical empirical techniques, present conditions under which wire's mass elasticity neglected. By accounting these effects, measure nichrome's to 17.1(1.3) ppm/K, is consistent with accepted...
Contact tracing can be an effective measure to control emerging infectious diseases, but the efficacy of contact measures depend upon willingness individuals get tested even when they are symptomatic. In this paper, we examine effects symptomatic getting and use in a network model disease transmission. We utilize resolve influence patterns between as apposed assuming mass action where all connected each other. find that self-reporting vary depending on structure network. also compare...
Two identical van der Pol oscillators with mutual inhibition are considered as a conceptual framework for modeling latching mechanism cell cycle regulation. In particular, the biased to latched state in which there is globally attracting steady-state equilibrium without coupling. The inhibitory coupling induces stable alternating large-amplitude oscillations that model normal cycle. A homoclinic bifurcation within found be responsible transition from cycling endocycles only one of two...