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- Walin, Gösta, 1938, et al.
(author)
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Source-related variables for the description of the oceanic carbon system
- 2014
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In: Geochemistry Geophysics Geosystems. - : American Geophysical Union (AGU). - 1525-2027. ; 15:9, s. 3675-3687
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Journal article (peer-reviewed)abstract
- The oceanic carbon system is commonly described in terms of the two state variables total carbon, DIC, and alkalinity, Alk. Here we suggest the use of alternative source adapted state variables, Acidic Carbon, AC and Basic Carbon, BC, defined by and related to (DIC, Alk) with a simple linear transformation. (AC, BC) can be interpreted as representing respectively the supply to the system of carbon dioxide and dissolved carbonate, keeping in mind that supply of hydrogen ions acts to transform from basic carbon to acidic carbon. Accordingly these variables tell us how much carbon dioxide or dissolved carbonate we actually have in the water, despite the fact that the major part of the carbon resides in bicarbonate ions. We claim that using these source-related variables as a compliment to the traditional variables, offers a number of advantages in the formulation of continuity equations, as well as in the interpretation of observations and modeling results. The traditional definition of alkalinity is related to a measuring procedure rather than to the supply of material to the system. Here we demonstrate that alkalinity, though defined in the traditional way, may be interpreted in terms of sources and sinks acting on the system. In the case of ocean water this amounts to twice the supply of dissolved carbonate minus the net supply of free hydrogen ions. We argue that this interpretation is a useful complement to the traditional definition. Every process that affects the state of the carbon system may be quantified in terms of supply of carbon dioxide, F-a, carbonate ions, F-b, or hydrogen ions, E.
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| 3. |
- Green, J. A. Mattias, et al.
(author)
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A comparison of tidal conversion parameterizations for tidal models
- 2013
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In: Journal of Physical Oceanography. - 0022-3670 .- 1520-0485. ; 43:1, s. 104-119
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Journal article (peer-reviewed)abstract
- The conversion of barotropic to baroclinic tidal energy in the global abyssal ocean is calculated using three different formulations. The calculations are done both offline, that is, using externally given tidal currents to estimate the energy conversion, and online, that is, by using the formulations to parameterize linear wave drag in a prognostic tidal model. All three schemes produce globally integrated offline dissipation rates beneath 500-m depth of similar to 0.6-0.8TW for the M-2 constituent, but the spatial structures vary significantly between the parameterizations. Detailed investigations of the energy transfer in local areas confirm the global results: there are large differences between the schemes, although the horizontally integrated conversion rates are similar. The online simulations are evaluated by comparing the sea surface elevation with data from the TOPEX/Poseidon database, and the error is then significantly lower when using the parameterization provided by Nycander than with the other two parameterizations examined.
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| 4. |
- Heifetz, Eyal, et al.
(author)
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Interacting vorticity waves as an instability mechanism for magnetohydrodynamic shear instabilities
- 2015
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In: Journal of Fluid Mechanics. - : Cambridge University Press (CUP). - 0022-1120 .- 1469-7645. ; 767, s. 199-225
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Journal article (peer-reviewed)abstract
- The interacting vorticity wave formalism for shear flow instabilities is extended here to the magnetohydrodynamic (MUD) setting, to provide a mechanistic description for stabilising and destabilising shear instabilities by the presence of a background magnetic field. The interpretation relies on local vorticity anomalies inducing a non-local velocity field, resulting in action at a distance. It is shown here that the waves supported by the system are able to propagate vorticity via the Lorentz force, and waves may interact. The existence of instability then rests upon whether the choice of basic state allows for phase locking and constructive interference of the vorticity waves via mutual interaction. To substantiate this claim, we solve the instability problem of two representative basic states, one where a background magnetic field stabilises an unstable flow and the other where the field destabilises a stable flow, and perform relevant analyses to show how this mechanism operates in MHD.
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| 5. |
- Kumar, Arvind, et al.
(author)
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Open Nodal Power Flow Model of the Nordic Power System
- 2021
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In: 2021 IEEE Madrid PowerTech, PowerTech 2021 - Conference Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- Lack of openly available power system data due to market regulations or corporate policies hinders the development of models for power system planning and operation studies. This work presents an open source model of the Nordic synchronous area (the Nordic490 model), which can be used for power flow calculations. To reach an accurate modelling of the Nordic transmission grid, the production and consumption time series are disaggregated based on demographics, and the values of certain network parameters and generation characteristics are investigated, by crosschecking various data sources. The resulting model is validated using open market data.
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| 8. |
- Nycander, J, et al.
(author)
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Turbulent equipartition and up-gradient transport
- 1996
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In: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; T63, s. 174-181
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Journal article (other academic/artistic)abstract
- Turbulent transport in tokamaks is often observed to be directed up-gradient. It is proposed that such up-gradient fluxes represent a tendency to approach turbulent equipartition (TEP). At TEP the phase space fluid is well mixed along surfaces defined by
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| 9. |
- Nycander, M, et al.
(author)
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Two-step mechanism of inhibition of cathepsin B by cystatin C, due to the inhibitor displacing the occluding loop of the enzyme
- 1998
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In: FEBS Letters. - 1873-3468. ; 422:1, s. 61-64
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Journal article (peer-reviewed)abstract
- Stopped-flow kinetics showed that the inhibition of the lysosomal cysteine proteinase, cathepsin B, by its endogenous inhibitor, cystatin C, occurs by a two-step mechanism, in which an initial, weak interaction is followed by a conformational change. The initial interaction most likely involves binding of the N-terminal region of the inhibitor to the proteinase. Considerable evidence indicates that the subsequent conformational change is due to the inhibitor displacing the occluding loop of the proteinase that partially obscures the active site. The presence of this loop, which allows the enzyme to function as an exopeptidase, thus complicates the inhibition mechanism, rendering cathepsin B much less susceptible than other cysteine proteinases to inhibition by cystatins.
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