Dynamically coupling system dynamics and SWAT+ models using Tinamït: application of modular tools for coupled human–water system models

Participatory water resource management requires modeling techniques that are accurate and flexible yet stakeholder-friendly. While different modeling frameworks offer advantages and disadvantages, system dynamics (SDs) models have seen sustained use as a stakeholder-friendly approach for participatory water resource modeling. Physically based models (e.g., SWAT+) have seen sustained use to model the hydrological components of water systems. Proposed as a way to combine the relative strengths of both modeling paradigms, model coupling allows researchers to, for example, build participatory SD models with stakeholders, while delegating the hydrological components of the overall model to an external hydrological model. Recently developed to facilitate model coupling, the Tinamït Python package presents an extensible, outward-facing application programming interface (API). It allows for the development of extensions (wrappers) that expand compatibility with different physically based models. However, no watershed hydrological model has yet been connected to this API. In the present study, a socket and JavaScript Object Notation (JSON)-based communication protocol was developed with the goal of facilitating the coupling of models written in languages such as Fortran. This novel protocol served to develop a Tinamït-compatible wrapper for the hydrological model SWAT+, allowing it to be coupled to human–water SD models. The novel coupling protocol was then applied to a case study of Tanzania's Usa river catchment. This approach provides the modeler with the benefits of both physically based and SD models, thereby allowing the detection of potentially far-reaching effects of policy-makers' decisions.</p

Properties of Graphene: A Theoretical Perspective

In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene from a theorist's perspective. We discuss the physical properties of graphene in an external magnetic field, reflecting the chiral nature of the quasiparticles near the Dirac point with a Landau level at zero energy. We address the unique integer quantum Hall effects, the role of electron correlations, and the recent observation of the fractional quantum Hall effect in the monolayer graphene. The quantum Hall effect in bilayer graphene is fundamentally different from that of a monolayer, reflecting the unique band structure of this system. The theory of transport in the absence of an external magnetic field is discussed in detail, along with the role of disorder studied in various theoretical models. We highlight the differences and similarities between monolayer and bilayer graphene, and focus on thermodynamic properties such as the compressibility, the plasmon spectra, the weak localization correction, quantum Hall effect, and optical properties. Confinement of electrons in graphene is nontrivial due to Klein tunneling. We review various theoretical and experimental studies of quantum confined structures made from graphene. The band structure of graphene nanoribbons and the role of the sublattice symmetry, edge geometry and the size of the nanoribbon on the electronic and magnetic properties are very active areas of research, and a detailed review of these topics is presented. Also, the effects of substrate interactions, adsorbed atoms, lattice defects and doping on the band structure of finite-sized graphene systems are discussed. We also include a brief description of graphane -- gapped material obtained from graphene by attaching hydrogen atoms to each carbon atom in the lattice.Comment: 189 pages. submitted in Advances in Physic

Electric double-layer capacitance between an ionic liquid and few-layer graphene

Ionic-liquid gates have a high carrier density due to their atomically thin electric double layer (EDL) and extremely large geometrical capacitance C-g. However, a high carrier density in graphene has not been achieved even with ionic-liquid gates because the EDL capacitance C-EDL between the ionic liquid and graphene involves the series connection of C-g and the quantum capacitance C-q, which is proportional to the density of states. We investigated the variables that determine C-EDL at the molecular level by varying the number of graphene layers n and thereby optimising C-q. The C-EDL value is governed by C-q at n, 4, and by C-g at n > 4. This transition with n indicates a composite nature for C-EDL. Our finding clarifies a universal principle that determines capacitance on a microscopic scale, and provides nanotechnological perspectives on charge accumulation and energy storage using an ultimately thin capacitor

Low Doses of Gamma-Irradiation Induce an Early Bystander Effect in Zebrafish Cells Which Is Sufficient to Radioprotect Cells

International audienceThe term ''bystander effect'' is used to describe an effect in which cells that have not been exposed to radiation are affected by irradiated cells though various intracellular signaling mechanisms. In this study we analyzed the kinetics and mechanisms of bystander effect and radioadaptation in embryonic zebrafish cells (ZF4) exposed to chronic low dose of gamma rays. ZF4 cells were irradiated for 4 hours with total doses of gamma irradiation ranging from 0.01-0.1 Gy. In two experimental conditions, the transfer of irradiated cells or culture medium from irradiated cells results in the occurrence of DNA double strand breaks in non-irradiated cells (assessed by the number of c-H2AX foci) that are repaired at 24 hours post-irradiation whatever the dose. At low total irradiation doses the bystander effect observed does not affect DNA repair mechanisms in targeted and bystander cells. An increase in global methylation of ZF4 cells was observed in irradiated cells and bystander cells compared to control cells. We observed that pre-irradiated cells which are then irradiated for a second time with the same doses contained significantly less c-H2AX foci than in 24 h gamma-irradiated control cells. We also showed that bystander cells that have been in contact with the pre-irradiated cells and then irradiated alone present less c-H2AX foci compared to the control cells. This radioadaptation effect is significantly more pronounced at the highest doses. To determine the factors involved in the early events of the bystander effect, we performed an extensive comparative proteomic study of the ZF4 secretomes upon irradiation. In the experimental conditions assayed here, we showed that the early events of bystander effect are probably not due to the secretion of specific proteins neither the oxidation of these secreted proteins. These results suggest that early bystander effect may be due probably to a combination of multiple factors

Diversity and distribution of groundwater fauna in a calcrete aquifer: does sampling method influence the story?

© CSIRO 2008There has been an increase in the number of studies examining the spatial and temporal patterns in species richness, community structure and population dynamics of groundwater organisms. These studies have raised the issue of uncertainty about the comparability of different sampling methods, and questions of whether sampling bias may exist. Recently, a diverse subterranean fauna was discovered in calcrete (carbonate) aquifers of the Yilgarn Region of central Western Australia. Little is known about the community structure and population dynamics in these aquifers. One important issue is whether current sampling methods adequately sample the species richness and abundance of the fauna to allow for comparative studies. Here we investigate the effectiveness of three sampling methods: haul net sampling, pumping with a 12-V impeller pump, and a discrete interval sampler. The methods were trialled over 16 months with &gt;250 samples taken from 55 uncased bore holes. No significant taxonomic bias was detected across the sampling methods. However, sampling using a haul net was found to be the most efficient method for capturing the available taxa per unit time when sampling bores are less than 10 m deep, with pumping being the least efficient. These results are discussed in relation to the problems of studying stygofauna in Western Australian calcrete aquifers, and of groundwater faunas more generally.Adam Allford, Steven J. B. Cooper, William F. Humphreys and Andrew D. Austi

Controlled hydrogenation of graphene sheets and nanoribbons

10.1021/nn102034yACS Nano52888-89

Toward ubiquitous environmental gas sensors—capitalizing on the promise of graphene

Atomically thin sheets of carbon known as &ldquo;graphene&rdquo; have captured the imagination of much of the scientific world during the past few years. Although these single sheets of graphite were under our noses for years&mdash;within technologies ranging from the humble pencil, which has been around since at least 1565 (Petroski, H. The Pencil: A History of Design and Circumstance; Alfred A. Knopf: New York, 1993), to modern nuclear reactors&mdash;graphene was merely considered as part of graphite&rsquo;s crystal structure until 2004, when Novoselov, Geim, and colleagues (Science 2004, 306, 666&minus;669) first presented some of the surprising electrical properties of graphene layers they had isolated by mechanically peeling sheets off graphite crystals. Today, graphene&rsquo;s unique electronic structures and properties, bolstered by other intriguing properties discovered in the intervening years, threaten the dominance of carbon nanotubes, a more mature allotrope of carbon, in potential applications from electronics to sensors. In this review, we will consider the promise of graphene for producing small-scale gas sensors for environmental monitoring.<br /