The Experts below are selected from a list of 4704 Experts worldwide ranked by ideXlab platform

Dennis J Mcgillicuddy - One of the best experts on this subject based on the ideXlab platform.

  • seasonal variation in the correlation between anomalies of sea level and chlorophyll in the antarctic circumpolar current
    Geophysical Research Letters, 2018
    Co-Authors: Hajoon Song, Matthew C Long, Peter Gaube, Ivy Frenger, John Marshall, Dennis J Mcgillicuddy
    Abstract:

    The Antarctic Circumpolar Current (ACC) has highly energetic Mesoscale Phenomena, but their impacts on phytoplankton biomass, productivity, and biogeochemical cycling are not understood well. We analyze satellite observations and an eddy‐rich ocean model to show that they drive chlorophyll anomalies of opposite sign in winter versus summer. In winter, deeper mixed layers in positive sea surface height (SSH) anomalies reduce light availability, leading to anomalously low chlorophyll concentrations. In summer with abundant light, however, positive SSH anomalies show elevated chlorophyll concentration due to higher iron level, and an iron budget analysis reveals that anomalously strong vertical mixing enhances iron supply to the mixed layer. Features with negative SSH anomalies exhibit the opposite tendencies: higher chlorophyll concentration in winter and lower in summer. Our results suggest that Mesoscale modulation of iron supply, light availability and vertical mixing plays an important role in causing systematic variations in primary productivity over the seasonal cycle.

  • mechanisms of physical biological biogeochemical interaction at the oceanic Mesoscale
    Annual Review of Marine Science, 2016
    Co-Authors: Dennis J Mcgillicuddy
    Abstract:

    Mesoscale Phenomena are ubiquitous and highly energetic features of ocean circulation. Their influence on biological and biogeochemical processes varies widely, stemming not only from advective transport but also from the generation of variations in the environment that affect biological and chemical rates. The ephemeral nature of Mesoscale features in the ocean makes it difficult to elucidate the attendant mechanisms of physical-biological-biogeochemical interaction, necessitating the use of multidisciplinary approaches involving in situ observations, remote sensing, and modeling. All three aspects are woven through this review in an attempt to synthesize current understanding of the topic, with particular emphasis on novel developments in recent years.

Claude Millot - One of the best experts on this subject based on the ideXlab platform.

  • circulation in the western mediterranean sea
    Journal of Marine Systems, 1999
    Co-Authors: Claude Millot
    Abstract:

    Abstract During the last decade, a considerable amount of work has been made and definite results obtained about the circulation in the Western Mediterranean Sea. The diagrams presented 10 years ago [Millot, C., 1987a. Circulation in the Western Mediterranean. Oceanol. Acta, 10, 2, 143–149.] have been confirmed and complemented, mainly in the south where all water masses appear to flow anticlockwise along the continental slope, as they do everywhere else in the sea. Definitive results have also been obtained about the Mesoscale Phenomena in the Algerian Basin which induce a dramatic variability of the circulation of all water masses, as far as around the Balearic Islands and through the Channel of Sardinia. Extremely interesting observations have been collected between Sicily, Tunisia and Sardinia about the hydrological and dynamical characteristics of the waters entering the Tyrrhenian Sea. Finally, the dense water formation processes have been specified, mainly since some uncommon situations have been encountered. As a whole, the relatively large importance of the seasonal (resp. Mesoscale) variability in the north (resp. south) has been documented. Together, the observations in nature, the laboratory experiments and the numerical models have thus provided a more thorough understanding of the sea dynamics. Nevertheless, uncertainties remain about the amount of the waters formed in the sea mainly at intermediate depths, for these waters are often not easily distinguished from the surrounding ones. This is of major importance for, a priori, intermediate waters can flow out of the sea more easily than deep waters. In any case, the southern Tyrrhenian Sea appears to be a key place for the functionning of the whole sea.

M A Anisimov - One of the best experts on this subject based on the ideXlab platform.

  • Mesoscale Phenomena in ternary solutions of tertiary butyl alcohol water and propylene oxide
    Journal of Physical Chemistry B, 2014
    Co-Authors: Deepa Subramanian, Jeffery B Klauda, Peter J Collings, M A Anisimov
    Abstract:

    The phase behavior and mesoscopic inhomogeneities in the ternary system of tertiary butyl alcohol (TBA), water, and propylene oxide (PO) have been studied by static and dynamic light scattering, gas chromatography, mass spectrometry, and molecular dynamics simulations. Mesoscale inhomogeneities are observed in this system in a broad range of PO concentrations, from 0.02 to about 65 mass %, and at certain TBA/water mass ratios varying from about 3/97 to about 30/70. This TBA/water composition domain corresponds to a region where short-lived micelle-like molecular clustering and thermodynamic anomalies are observed in the TBA-water binary system. At dilute PO concentrations (0.02 to about 1 mass %) the Mesoscale inhomogeneities are Brownian diffusive droplets, with a size of the order of a hundred nanometers. We hypothesize that these droplets have a hydrophobic core enriched by oily impurities and oligomerized PO molecules. A hydrogen-bonded layer of TBA, water, and PO molecules surrounds this hydrophobic core. At high PO concentrations (beyond 50 mass %), the interfacial curvature of the mesoscopic inhomogeneities changes its sign and the exteriors of these inhomogeneities become hydrophobic. The inversion of the internal curvature may result in the formation of a spongelike bicontinuous Mesoscale structure at intermediate PO concentrations. This mesostructure appears to be at a nonequilibrium state, although extremely long-lived.

  • Mesoscale Phenomena in solutions of 3 methylpyridine heavy water and an antagonistic salt
    Soft Matter, 2013
    Co-Authors: Jan Leys, Deepa Subramanian, Eva Rodezno, Boualem Hammouda, M A Anisimov
    Abstract:

    We have investigated controversial issues regarding the Mesoscale behavior of 3-methylpyridine (3MP), heavy water, and sodium tetraphenylborate (NaBPh4) solutions by combining results obtained from dynamic light scattering (DLS) and small-angle neutron scattering (SANS). We have addressed three questions: (i) what is the origin of the Mesoscale inhomogeneities (order of 100 nm in size) manifested by the “slow mode” in DLS? (ii) Is the periodic structure observed from SANS an inherent property of this system? (iii) What is the universality class of critical behavior in this system? Our results confirm that the “slow mode” observed from DLS experiments corresponds to long-lived, highly stable Mesoscale droplets (order of 100 nm in size), which occur only when the solute (3MP) is contaminated by hydrophobic impurities. SANS data confirm the presence of a periodic structure with a periodicity of about 10 nm. This periodic structure cannot be eliminated by nanopore filtration and thus is indeed an inherent solution property. The critical behavior of this system, in the range of concentration and temperatures investigated by DLS experiments, indicates that the criticality belongs to the universality class of the 3-dimensional Ising model.

Rhj Ron Peerlings - One of the best experts on this subject based on the ideXlab platform.

  • a multiscale quasicontinuum method for lattice models with bond failure and fiber sliding
    Computer Methods in Applied Mechanics and Engineering, 2014
    Co-Authors: Laa Lars Beex, Rhj Ron Peerlings, Mgd Marc Geers
    Abstract:

    Structural lattice models incorporating trusses and beams are frequently used to mechanically model fibrous materials, because they can capture (local) Mesoscale Phenomena. Physically relevant lattice computations are however computationally expensive. A suitable multiscale approach to reduce the computational cost of large-scale lattice computations is the quasicontinuum (QC) method. This method resolves local Mesoscale Phenomena in regions of interest and coarse grains elsewhere, using only the lattice model. In previous work, a virtual-power-based QC framework is proposed for lattice models that include local dissipative mechanisms. In this paper, the virtual-power-based QC method is adopted for lattice models in which bond failure and subsequent frictional fiber sliding are incorporated – which are of significant importance for fibrous materials such as paper, cardboard, textile and electronic textile. Bond failure and fiber sliding are nonlocal dissipative mechanisms and to deal with this nonlocality, the virtual-power-based QC method is equipped with a mixed formulation in which the kinematic variables as well as the internal history variables are interpolated. Previously defined summation rules can still be used to sample the governing equations in this QC framework. Illustrative examples are presented.

  • a discrete network model for bond failure and frictional sliding in fibrous materials
    International Journal of Solids and Structures, 2013
    Co-Authors: D V Wilbrink, Laa Lars Beex, Rhj Ron Peerlings
    Abstract:

    Discrete network models and lattice models using trusses or beams can be used to mechanically model fibrous materials, since the discrete elements represent the individual fibers or yarns at the Mesoscale of these materials. Consequently, local Mesoscale Phenomena, such as individual fiber failure and interfiber bond failure, can be incorporated. Only a few discrete network models in which bond failure is incorporated include frictional fiber sliding that occurs after bond failure has taken place, although this occurs in the mechanical behaviour of several fibrous materials. In this paper, a spring network model for interfiber bond failure and subsequent frictional fiber sliding is developed, which is formulated in a thermodynamical setting. The thermodynamical basis ensures that performed mechanical work is either stored in the network or dissipated due to bond failure and subsequent sliding. A numerical implementation of the framework is proposed in which the kinematic and internal variables are simultaneously solved, because the internal variables are directly coupled in the framework. Variations in network connectivity, bond strength, fiber length and anisotropy are implemented in the framework. The results show amongst others that the macroscopic yield point scales with the bond strength and that the macroscopic stiffness and the macroscopic yield point scale with the fiber length. The presented results also show that the macroscopic yield point becomes significantly less pronounced for an increase of the fiber length.

Josep Vivesrego - One of the best experts on this subject based on the ideXlab platform.

  • mathematical modelling methodologies in predictive food microbiology a swot analysis
    International Journal of Food Microbiology, 2009
    Co-Authors: Jordi Ferrer, Clara Prats, Daniel Lopez, Josep Vivesrego
    Abstract:

    Abstract Predictive microbiology is the area of food microbiology that attempts to forecast the quantitative evolution of microbial populations over time. This is achieved to a great extent through models that include the mechanisms governing population dynamics. Traditionally, the models used in predictive microbiology are whole-system continuous models that describe population dynamics by means of equations applied to extensive or averaged variables of the whole system. Many existing models can be classified by specific criteria. We can distinguish between survival and growth models by seeing whether they tackle mortality or cell duplication. We can distinguish between empirical (phenomenological) models, which mathematically describe specific behaviour, and theoretical (mechanistic) models with a biological basis, which search for the underlying mechanisms driving already observed Phenomena. We can also distinguish between primary, secondary and tertiary models, by examining their treatment of the effects of external factors and constraints on the microbial community. Recently, the use of spatially explicit Individual-based Models (IbMs) has spread through predictive microbiology, due to the current technological capacity of performing measurements on single individual cells and thanks to the consolidation of computational modelling. Spatially explicit IbMs are bottom–up approaches to microbial communities that build bridges between the description of micro-organisms at the cell level and macroscopic observations at the population level. They provide greater insight into the Mesoscale Phenomena that link unicellular and population levels. Every model is built in response to a particular question and with different aims. Even so, in this research we conducted a SWOT (Strength, Weaknesses, Opportunities and Threats) analysis of the different approaches (population continuous modelling and Individual-based Modelling), which we hope will be helpful for current and future researchers.

  • mathematical modelling methodologies in predictive food microbiology a swot analysis
    International Journal of Food Microbiology, 2009
    Co-Authors: Jordi Ferrer, Clara Prats, Daniel Lopez, Josep Vivesrego
    Abstract:

    Abstract Predictive microbiology is the area of food microbiology that attempts to forecast the quantitative evolution of microbial populations over time. This is achieved to a great extent through models that include the mechanisms governing population dynamics. Traditionally, the models used in predictive microbiology are whole-system continuous models that describe population dynamics by means of equations applied to extensive or averaged variables of the whole system. Many existing models can be classified by specific criteria. We can distinguish between survival and growth models by seeing whether they tackle mortality or cell duplication. We can distinguish between empirical (phenomenological) models, which mathematically describe specific behaviour, and theoretical (mechanistic) models with a biological basis, which search for the underlying mechanisms driving already observed Phenomena. We can also distinguish between primary, secondary and tertiary models, by examining their treatment of the effects of external factors and constraints on the microbial community. Recently, the use of spatially explicit Individual-based Models (IbMs) has spread through predictive microbiology, due to the current technological capacity of performing measurements on single individual cells and thanks to the consolidation of computational modelling. Spatially explicit IbMs are bottom–up approaches to microbial communities that build bridges between the description of micro-organisms at the cell level and macroscopic observations at the population level. They provide greater insight into the Mesoscale Phenomena that link unicellular and population levels. Every model is built in response to a particular question and with different aims. Even so, in this research we conducted a SWOT (Strength, Weaknesses, Opportunities and Threats) analysis of the different approaches (population continuous modelling and Individual-based Modelling), which we hope will be helpful for current and future researchers.