Alfv\'en-dynamo balance and magnetic excess in MHD turbulence

3D Magnetohydrodynamic (MHD) turbulent flows with initially magnetic and kinetic energies at equipartition spontaneously develop a magnetic excess (or residual energy), as well in numerical simulations and in the solar wind. Closure equations obtained in 1983 describe the residual spectrum as being produced by a dynamo source proportional to the total energy spectrum, balanced by a linear Alfv\'en damping term. A good agreement was found in 2005 with incompressible simulations; however, recent solar wind measurements disagree with these results. The previous dynamo-Alfv\'en theory is generalized to a family of models, leading to simple relations between residual and total energy spectra. We want to assess these models in detail against MHD simulations and solar wind data. The family of models is tested against compressible decaying MHD simulations with low Mach number, low cross-helicity, zero mean magnetic field, without or with expansion terms (EBM or expanding box model). A single dynamo-Alfv\'en model is found to describe correctly both solar wind scalings and compressible simulations without or with expansion. It is equivalent to the 1983-2005 closure equation but with critical balance of nonlinear turnover and linear Alfv\'en times, while the dynamo source term remains unchanged. The discrepancy with previous incompressible simulations is elucidated. The model predicts a linear relation between the spectral slopes of total and residual energies $m_R = -1/2 + 3/2 m_T$. Examining the solar wind data as in \cite{2013ApJ...770..125C}, our relation is found to be valid whatever the cross-helicity, even better so at high cross-helicity, with the total energy slope varying from $1.7$ to $1.55$.Comment: 7 pages, 7 figures, accepted for publication in A&

Stimulation of a glycosyl-phosphatidylinositol-specific phospholipase by insulin and the sulfonylurea, glimepiride, in rat adipocytes depends on increased glucose transport

Abstract. Lipoprotein lipase (LPL) and glycolipidanchored cAMP-binding ectoprotein (Gcel) are modified by glycosyl-phosphatidylinositol (GPI) in rat adipocytes, however, the linkage is potentially unstable. Incubation of the cells with either insulin (0.1-30 nM) or the sulfonylurea, glimepiride (0.5-20/zM), in the presence of glucose led to conversion of up to 35 and 20%, respectively, of the total amphiphilic LPL and Gcel to their hydrophilic versions. Inositol-phosphate was retained in the residual protein-linked anchor structure. This suggests cleavage of the GPI anchors by an endogenous GPI-specific insulin- and glimepiride-inducible phospholipase (GPI-PL). Despite cleavage, hydrophilic LPL and Creel remained membrane associated and were released only if a competitor, e.g., inositol-(cyclic)monophosphate, had been added. Other constituents of the GPI anchor (glucosamine and mannose) were less efficient. This suggests reat body of information exists regarding the structural diversity as well as the biosynthesis and posttranslational attachment of glycosyl-phosphatidylinositol (GPI) ~ structures (for recent reviews see Low, 1989; McConville et al., 1993). However, the functional significance of membrane anchorage via GPI structures versus transmembrane polypeptide domains is still a matter of debate. The accessibility of GPI molecules to cleavage by phospholipase [(G)PI-PL] opens the possibility of a regu-Address all correspondence to Dr. (;tinter Miiller, Hoechst AG Frankfurt

Humpback whales, rock lobsters and mathematics : exploration of assessment models incorporating stock-structure

This thesis presents four marine resource assessments; three concern the Southern Hemisphere (SH) humpback whale (Megaptera novaeangliae) and one the South African east coast rock lobster Palinurus delagoae. It also sets out the statistical background to the methodology employed in the assessments, including an outline of the Bayesian approach, Bayes' theorem, and the sampling-importance re-sampling (SIR) as well as the Markov Chain Monte Carlo (MCMC) methods

Three-dimensional Iroshnikov-Kraichnan turbulence in a mean magnetic field

Forced, weak MHD turbulence with guide field is shown to adopt different regimes, depending on the magnetic excess of the large forced scales. When the magnetic excess is large enough, the classical perpendicular cascade with $5/3$ scaling is obtained, while when equipartition is imposed, an isotropic $3/2$ scaling appears in all directions with respect to the mean field (\cite{2010PhRvE..82b6406G} or GM10). We show here that the $3/2$ scaling of the GM10 regime is not ruled by a small-scale cross-helicity cascade, and propose that it is a 3D extension of a perpendicular weak Iroshnikov-Kraichnan (IK) cascade. We analyze in detail the structure functions in real space and show that they closely follow the critical balance relation both in the local frame and the global frame: we show that there is no contradiction between this and the isotropic $3/2$ scaling of the spectra. We propose a scenario explaining the spectral structure of the GM10 regime, that starts with a perpendicular weak IK cascade and extends to 3D by using quasi-resonant couplings. The quasi-resonance condition happens to reduce the energy flux in the same way as is done in the weak perpendicular cascade, so leading to a $3/2$ scaling in all directions. We discuss the possible applications of these findings to solar wind turbulence.Comment: Major re-write of manuscrip

Thermalization and many-body localization in systems under dynamic nuclear polarization

We study the role of dipolar interactions in the standard protocol used to achieve dynamic nuclear polarization (DNP). In the so-called spin-temperature regime, where the interactions establish an effective thermodynamic behavior in the out-of-equilibrium stationary state, we provide numerical predictions for the level of hyperpolarization. We show that nuclear spins equilibrate to the effective spin-temperature established among the electron spins of radicals, as expected from the quantum theory of thermalization. Moreover, we present an analytical technique to estimate the spin temperature, and thus, the nuclear hyperpolarization in the steady state, as a function of interaction strength and quenched disorder. This reproduces both our numerical data and experimental results. Our central finding is that the nuclear hyperpolarization increases steadily upon reducing the interaction strength (by diluting the radical density). Interestingly, the highest polarization is reached at a point where the establishment of a spin temperature is just about to break down due to the incipient many-body localization transition in the electron spin system.Comment: 12 pages (+ 3 pages of appendix), 8 figure

Anisotropy of third-order structure functions in MHD turbulence

The measure of the third-order structure function, Y, is employed in the solar wind to compute the cascade rate of turbulence. In the absence of a mean field B0=0, Y is expected to be isotropic (radial) and independent of the direction of increments, so its measure yields directly the cascade rate. For turbulence with mean field, as in the solar wind, Y is expected to become more two dimensional (2D), that is, to have larger perpendicular components, loosing the above simple symmetry. To get the cascade rate one should compute the flux of Y, which is not feasible with single-spacecraft data, thus measurements rely upon assumptions about the unknown symmetry. We use direct numerical simulations (DNS) of magneto-hydrodynamic (MHD) turbulence to characterize the anisotropy of Y. We find that for strong guide field B0=5 the degree of two-dimensionalization depends on the relative importance of shear and pseudo polarizations (the two components of an Alfv\'en mode in incompressible MHD). The anisotropy also shows up in the inertial range. The more Y is 2D, the more the inertial range extent differs along parallel and perpendicular directions. We finally test the two methods employed in observations and find that the so-obtained cascade rate may depend on the angle between B0 and the direction of increments. Both methods yield a vanishing cascade rate along the parallel direction, contrary to observations, suggesting a weaker anisotropy of solar wind turbulence compared to our DNS. This could be due to a weaker mean field and/or to solar wind expansion.Comment: Some text editing and typos corrected, 13 pages, 6 figures, to be published in Ap

Risk and sustainability assessment (RSA) framework for ‘water scarcity – water reuse’ situations: Conceptualisation, operationalisation, and testing

The number of regions undergoing water scarcity, where the quantity of available water is not enough to meet human demand, is expected to increase in the future. Water reuse measures have been widely implemented to face these situations as a means of increasing the supply of water resources. Thus, ‘water scarcity – water reuse’ (WS-WR) situations will likely become more common. In these cases, water resources management to secure enough water supply is key. Risk and sustainability concepts have been consolidated as guiding discourses that also support the management of water resources. In particular, in the case of WS-WR situations, they can guide decision-makers towards reducing the risk of water scarcity and striving for the implementation of sustainable water reuse measures. In particular, the use of risk and sustainability assessments helps to deal with various social, economic, and environmental requirements and constraints. However, there is still the call for a more comprehensive and integrated assessments. This dissertation aims at providing new ideas for the integration of risk and sustainability in the case of WS-WR situations. Three objectives guide this research: (A) to develop a conceptual assessment framework to support decision-making concerning sustainable water reuse in regions facing risk of water scarcity; (B) to advance the conceptual framework interrelating existing risk and sustainability assessment methodologies and indicators in the context of decision support; and (C) to test the conceptual and methodological framework using a case study in Latin America. Each objective is associated with a research question: (RQ1) How is decision-making regarding water reuse understood and supported towards reducing the risk of water scarcity sustainably – and how can it be represented in a conceptual assessment framework?; (RQ2) How can a conceptual framework for assessing water reuse as sustainable water scarcity risk reduction measures be operationalised through a methodological framework?; and (RQ3) What are the findings from testing the framework in a case study – and what can be incorporated into the framework? Each objective and its respective research question was addressed as a separate step of the research approach, comprising the development of an integrated Risk and Sustainability Assessment (RSA) Framework for WS-WR situations, its operationalisation and testing. The research approach followed a deductive to inductive rationale relying on qualitative and quantitative methods. The outputs of this research are three scientific publications that build this cumulative dissertation (two published and one submitted for revision). The development of the conceptual framework followed three steps: (i) defining the concepts of ‘water scarcity’, ‘water reuse’, ‘risk’ and ‘risk assessment’, ‘sustainability’ and ‘sustainability assessment’, and ‘decision-making’; (ii) integrating these concepts by interpreting water scarcity from a risk perspective and water reuse from a sustainability perspective, and relating assessments with decision-making; and (iii) structuring the RSA Framework, following a risk assessment and framing it by the social, economic, and environmental dimensions of sustainability. Results allowed defining decision-making in WS-WR situations as a four-step cyclic process that can be supported by an integrated RSA that comprises an analysis (descriptive and objective) and evaluation (subjective). The methodological aspects for the operationalisation of the RSA conceptual framework focused mainly on developing an analytical concept to support an adequate derivation of the information required in an integrated RSA for WS-WR situations. The resulting concept is based on (i) understanding the WS-WR situation as a Coupled Human and Natural System (CHANS) and identifying the main biophysical elements (endpoints); (ii) translating the CHANS endpoints into an information system via a Multi-Layer (ML) approach using generic descriptors and specific indicators; and (iii) identifying and characterising interlinkages between the indicators via a Lane-Based (LB) approach. Additional methodological aspects related to the evaluation include the use of indicator-based multi-criteria decision-making methods that include the weighting and aggregation of these indicators, as well as the selection of threshold values as evaluation criteria. The testing of the integrated RSA Framework was carried out in Cerrillos de Tamaya, Chile. It involved an ex-post RSA of a water reuse measure implemented in 2018 to face the local water scarcity situation. The testing included (i) describing the case study location and adapting the RSA Framework to fit the local context; (ii) translating the case study’s CHANS via the ML approach and identifying and characterising interlinkages via the LB approach; and (iii) evaluating the degree of risk of water scarcity and sustainability of water reuse via the distance-based method TOPSIS. The results of the testing provided feedback for the RSA Framework. These mainly referred to the influence of the conceptualisation behind the indicators and their use, and the methodological challenges for integrating risk and sustainability evaluation. Further recommendations to the RSA framework are: the inclusion of interlinkage directionality; the use of existing system dynamics modelling approaches (e.g., CLD, SFD); the development of an established database of indicators; the automation of the interlinkages analysis (LB approach); and advance the use of scenarios for sustainability evaluation for better coupling with risk evaluation methods. Overall this research provides evidence of (a) the conceptual integration of risk and sustainability discourses under one decision support framework for the case of WS-WR situations; (b) the use of a system thinking approach for interpreting the WS-WR situation; (c) the relevance of indicators as a means of representing the situation; (d) the interlinkage of social, economic, environmental information; (e) the benefits of the use of conceptual maps; (f) gaps in the process of measuring the effect of water reuse on water scarcity levels via indicators; (g) the gap between a simulation-based risk assessment and a snapshot-focused sustainability assessment that hinders an operational integration; (h) the possibility of the RSA framework to bridge a system thinking view with a traditional assessment-based decision-making view.:Acknowledgements Abstract Contents List of Figures List of Tables Acronyms and Abbreviations Symbols Chapter 1 - Introduction 1.1 Background and problem statement 1.1.1 Water resources for water security 1.1.2 Risk and sustainability discourses for water-related decision-making 1.1.3 Problem statement and research focus 1.2 Objectives and research questions 1.3 Research approach and structure of the document 1.3.1 Research approach 1.3.2 Structure of the document 1.4 Chapter references Chapter 2 - Conceptual Framework 2.1 Introduction 2.2 Developing the conceptual framework 2.2.1 Definition and interpretation of the subject at stake 2.2.2 Identification and definition of key concepts 2.2.3 Construction of the conceptual framework 2.3 Results and discussion 2.3.1 Defining and interpreting the ‘water scarcity – water reuse’ situation 2.3.2 Identifying and defining key concepts 2.3.3 Construction of the integrated RSA Framework 2.4 Conclusions and outlook 2.5 Acknowledgements 2.6 Chapter references Chapter 3 - Methodological Aspects 3.1 Introduction 3.2 RSA Framework for a WS-WR situation 3.3 Systems thinking in a WS-WR situation 3.3.1 Identifying elements of a WS-WR situation and its interpretation as a system 3.3.2 Translation of the CHANS into an information system 3.4 Characterisation and interlinkage of indicators 3.4.1 Type and number of indicators 3.4.2 Type and number of interlinkages 3.4.3 Indicator connectivity 3.4.4 Structuring via a lane-based approach 3.5 RSA analytical concept and exemplification 3.5.1 RSA analytical concept 3.5.2 Exemplification of the analyitical concept 3.6 Discussion 3.6.1 Translating the CHANS into an information system 3.6.2 Supporting decision-making via the analytical concept 3.7 Conclusions 3.8 Acknowledgements 3.9 Chapter references Chapter 4 - Framework Testing 4.1 Introduction 4.2 Approach 4.2.1 RSA Framework 4.2.2 Case study site 4.3 Results 4.3.1 Analysis 4.3.2 Evaluation 4.3.3 General results for the case 4.4 Discussion 4.4.1 Analysis 4.4.2 Evaluation 4.4.3 Overall discussion on the testing of the RSA Framework 4.5 Conclusions 4.6 Acknowledgements 4.7 Chapter References Chapter 5 - Synthesis 5.1 Conceptual aspects 5.2 Methodological aspects 5.3 Testing aspects 5.4 Placing the RSA Framework in a broader context 5.5 Chapter References Chapter 6 - Conclusions and Outlook Annexes Annex A - Literature review: Found records Annex B - Example list of endpoints, descriptors, indicators, and attributes Annex C - Technique for Order Preference by Similarly to Ideal Solution (TOPSIS) Annex D - Translation into the Information System (from endpoints to attributes) Annex E - Interlinkages Identification Matrix Annex F - List of Most Interlinked Indicators (MII) Annex G - List of indicators, scores, and threshold