Fast Fourier Transform Simulation Techniques for Coulomb Gases

An improved approach to updating the electric field in simulations of Coulomb gases using the local lattice technique introduced by Maggs and Rossetto, is described and tested. Using the Fast Fourier Transform (FFT) an independent configuration of electric fields subject to Gauss' law constraint can be generated in a single update step. This FFT based method is shown to outperform previous approaches to updating the electric field in the simulation of a basic test problem in electrostatics of strongly correlated systems.Comment: 5 pages, 3 figure

Boundary conditions in local electrostatics algorithms

We study the simulation of charged systems in the presence of general boundary conditions in a local Monte Carlo algorithm based on a constrained electric field. We firstly show how to implement constant-potential, Dirichlet, boundary conditions by introducing extra Monte Carlo moves to the algorithm. Secondly, we show the interest of the algorithm for studying systems which require anisotropic electrostatic boundary conditions for simulating planar geometries such as membranes.Comment: 8 pages, 6 figures, accepted in JC

Simulating nanoscale dielectric response

We introduce a constrained energy functional to describe dielectric response. We demonstrate that the local functional is a generalization of the long ranged Marcus energy. Our re-formulation is used to implement a cluster Monte Carlo algorithm for the simulation of dielectric media. The algorithm avoids solving the Poisson equation and remains efficient in the presence of spatial heterogeneity, nonlinearity and scale dependent dielectric properties.Comment: 4 pages, 2 figures. Revtex

Anisotropic elasticity in confocal studies of colloidal crystals

We consider the theory of fluctuations of a colloidal solid observed in a confocal slice. For a cubic crystal we study the evolution of the projected elastic properties as a function of the anisotropy of the crystal using numerical methods based on the fast Fourier transform. In certain situations of high symmetry we find exact analytic results for the projected fluctuations.Comment: 6 pages, 7 figure

Local Simulation Algorithms for Coulombic Interactions

We consider dynamically constrained Monte-Carlo dynamics and show that this leads to the generation of long ranged effective interactions. This allows us to construct a local algorithm for the simulation of charged systems without ever having to evaluate pair potentials or solve the Poisson equation. We discuss a simple implementation of a charged lattice gas as well as more elaborate off-lattice versions of the algorithm. There are analogies between our formulation of electrostatics and the bosonic Hubbard model in the phase approximation. Cluster methods developed for this model further improve the efficiency of the electrostatics algorithm.Comment: Proceedings Statphys22 10 page

Linking equity, power, and stakeholders’ roles in relation to ecosystem services

The issues of power and equity are gaining attention in research on ecosystem services (ESs). Stakeholders benefiting from ESs are not necessarily able or authorized to participate in ES management. Thus, we have proposed an analytical framework to identify and qualify stakeholders' roles in relation to ES flows. Building on existing frameworks in the ES literature, we aimed to unravel the different direct and indirect management contributions to ES flows and link them to ES benefits. Direct management targets the functioning of ecosystems, the flows of services, and the benefits received by society, whereas indirect management facilitates, controls, or restricts the activities of direct managers. We applied this framework to the Mariño watershed (Peru) to describe stakeholders' roles using a set of 8 ESs. We have discussed the implications of our findings in terms of equity and power distribution. We conducted face-to-face semistructured interviews with representatives of 52 watershed stakeholders to understand how they managed and benefited from ESs. We used statistical analysis (permutation tests) to detect significant differences in the number of received and managed ESs among stakeholder sectors, i.e., civil society, nongovernmental organizations (NGOs), business, and the public sector, and scales, from local to national levels. Indirect forms of ES management were more frequent than direct ones for all ESs. Water quantity, water quality, and agricultural production were managed by the largest number of stakeholder types. The differences in the number of stakeholder types benefiting from and managing ESs could result from intentional choices, e.g., preferences for local benefits. We also found clear differences in the identity of stakeholders who managed or benefited from ESs. Local stakeholders and the business sector benefited from a higher number of ESs, and public organizations and NGOs were most involved in ES management. More equitable governance of ESs should aim to integrate more diverse stakeholders into decision making. Further empirical research could use our framework to explore the factors determining stakeholders' roles and power distribution. There is a particular need to understand how rights, endowments, and entitlements, as well as spatial configuration, underpin inequities in different social and cultural contexts

Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies

A single particle instrument was developed for real-time analysis of organic aerosol. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized by using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE ranges from 0.1 to 90% for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. During optical detection, particle scattered light from the two diode lasers, is detected by two photomultipliers and the detected signals are used to trigger UV excimer laser (λ = 248 nm) used for one-step laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 × 10<sup>−15</sup> kg (∼4 × 10<sup>3</sup> molecules). DOP particles were also used to test the overall operation of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first application of the instrument. Single particle mass spectra were obtained with an effective hit rate of 8%. Some of these mass spectra were found to be very different from one particle to another possibly reflecting chemical differences within the investigated indene SOA particles. Our study shows that an exhaustive statistical analysis, over hundreds of particles, and adapted reference mass spectra are further needed to understand the chemical meaning of single particle mass spectra of chemically complex submicrometer-sized organic aerosols