A 1-D modelling of streaming potential dependence on water content during drainage experiment in sand

The understanding of electrokinetics for unsaturated conditions is crucial for numerous of geophysical data interpretation. Nevertheless, the behaviour of the streaming potential coefficient C as a function of the water saturation Sw is still discussed. We propose here to model both the Richards' equation for hydrodynamics and the Poisson's equation for electrical potential for unsaturated conditions using 1-D finite element method. The equations are first presented and the numerical scheme is then detailed for the Poisson's equation. Then, computed streaming potentials (SPs) are compared to recently published SP measurements carried out during drainage experiment in a sand column. We show that the apparent measurement of DV / DP for the dipoles can provide the SP coefficient in these conditions. Two tests have been performed using existing models for the SP coefficient and a third one using a new relation. The results show that existing models of unsaturated SP coefficients C(Sw) provide poor results in terms of SP magnitude and behaviour. We demonstrate that the unsaturated SP coefficient can be until one order of magnitude larger than Csat, its value at saturation. We finally prove that the SP coefficient follows a non-monotonous behaviour with respect to water saturation. Key words: Electrical properties; Electromagnetic theory; Hydrogeophysics; Hydrology; Permeability and porosity; electrokinetic; streaming potential; self-potential; water content; water saturation; unsaturated condition; finite element modelin

Hollywood studio filmmaking in the age of Netflix: a tale of two institutional logics

Abstract: Online streaming services are challenging long-standing decision-making processes in the traditional motion picture industry, thus placing Hollywood major studios at a crossroads. We use the institutional logics perspective to examine how both traditional studios and online streaming services make strategic decisions on which films to produce and how these films are to be distributed. We then apply scenario analysis to explore how their interaction will likely evolve. We argue that the key criteria that studio executives use to make production and distribution decisions are shaped by what we define as a commitment institutional logic: decision-making heuristics that focus their attention on theatrical release and box-office intakes. In contrast, online streaming services follow a convenience institutional logic, the product of advanced data analytics to increase subscriptions. In the convenience institutional logic, the need to drive online traffic by providing users with an extensive catalogue of movies guides film production and distribution decisions. Whereas the commitment logic aims for mass-market hits in cinemas, the convenience logic seeks to reach a wide range of subscribers at home with micro-segmented offerings. We compare the two logics, develop four scenarios of how the interaction between them may shape the film industry, and offer recommendations

Tri-critical behavior in rupture induced by disorder

We discover a qualitatively new behavior for systems where the load transfer has limiting stress amplification as in real fiber composites. We find that the disorder is a relevant field leading to tri--criticality, separating a first-order regime where rupture occurs without significant precursors from a second-order regime where the macroscopic elastic coefficient exhibit power law behavior. Our results are based on analytical analysis of fiber bundle models and numerical simulations of a two-dimensional tensorial spring-block system in which stick-slip motion and fracture compete.Comment: Revtex, 10 pages, 4 figures available upon reques

Scale relativity and fractal space-time: theory and applications

In the first part of this contribution, we review the development of the theory of scale relativity and its geometric framework constructed in terms of a fractal and nondifferentiable continuous space-time. This theory leads (i) to a generalization of possible physically relevant fractal laws, written as partial differential equation acting in the space of scales, and (ii) to a new geometric foundation of quantum mechanics and gauge field theories and their possible generalisations. In the second part, we discuss some examples of application of the theory to various sciences, in particular in cases when the theoretical predictions have been validated by new or updated observational and experimental data. This includes predictions in physics and cosmology (value of the QCD coupling and of the cosmological constant), to astrophysics and gravitational structure formation (distances of extrasolar planets to their stars, of Kuiper belt objects, value of solar and solar-like star cycles), to sciences of life (log-periodic law for species punctuated evolution, human development and society evolution), to Earth sciences (log-periodic deceleration of the rate of California earthquakes and of Sichuan earthquake replicas, critical law for the arctic sea ice extent) and tentative applications to system biology.Comment: 63 pages, 14 figures. In : First International Conference on the Evolution and Development of the Universe,8th - 9th October 2008, Paris, Franc

A Study of the Day - Night Effect for the Super - Kamiokande Detector: I. Time Averaged Solar Neutrino Survival Probability

This is the first of two articles aimed at providing comprehensive predictions for the day-night (D-N) effect for the Super-Kamiokande detector in the case of the MSW \nu_e \to \numt transition solution of the solar neutrino problem. The one-year averaged probability of survival of the solar \nue crossing the Earth mantle, the core, the inner 2/3 of the core, and the (core + mantle) is calculated with high precision (better than 1%) using the elliptical orbit approximation (EOA) to describe the Earth motion around the Sun. Results for the survival probability in the indicated cases are obtained for a large set of values of the MSW transition parameters $\Delta m^2$ and $sin^22\theta_{V}$ from the ``conservative'' regions of the MSW solution, derived by taking into account possible relatively large uncertainties in the values of the $^{8}$B and $^{7}$Be neutrino fluxes. Our results show that the one-year averaged D-N asymmetry in the $\nu_e$ survival probability for neutrinos crossing the Earth core can be, in the case of $sin^22 \theta_{V} \leq 0.13$, larger than the asymmetry in the probability for (only mantle crossing + core crossing) neutrinos by a factor of up to six. The enhancement is larger in the case of neutrinos crossing the inner 2/3 of the core. This indicates that the Super-Kamiokande experiment might be able to test the $sin^22\theta_{V} \leq 0.01$ region of the MSW solution of the solar neutrino problem by performing selective D-N asymmetry measurements.Comment: LaTeX2e - 18 Text Pages + 21 figures = 39 Pages. - Figures in PS + text file sk1b14.tex requires two auxiliary files (included

Dragon-kings: mechanisms, statistical methods and empirical evidence

This introductory article presents the special Discussion and Debate volume "From black swans to dragon-kings, is there life beyond power laws?" published in Eur. Phys. J. Special Topics in May 2012. We summarize and put in perspective the contributions into three main themes: (i) mechanisms for dragon-kings, (ii) detection of dragon-kings and statistical tests and (iii) empirical evidence in a large variety of natural and social systems. Overall, we are pleased to witness significant advances both in the introduction and clarification of underlying mechanisms and in the development of novel efficient tests that demonstrate clear evidence for the presence of dragon-kings in many systems. However, this positive view should be balanced by the fact that this remains a very delicate and difficult field, if only due to the scarcity of data as well as the extraordinary important implications with respect to hazard assessment, risk control and predictability.Comment: 20 page

Improvisation and Transformation: Yes to the Mess

The field of organizational change has chiefly been studied from a teleological perspective. Most models of change emphasize action that is rational and goal oriented. What often gets overlooked and under theorized is the continuous, iterative nature of organizational life, the unplanned and serendipitous actions by and between people that lead to new discoveries and innovation. Recent research on organizational improvisation seeks to explore this area. In this chapter we will address two questions – what is the experience of improvisation and what are the conditions that support improvisation to flourish in organizations? In the first part of this paper, we look at the phenomenology of improvisation, the actual lived experience of those who improvise in the face of the unknown or in the midst of chaotic conditions. We will explore the strategies that some professional improvisers employ to deliberately create the improvisatory moment. We will then look at the dynamics of organizational life and explore the cultural beliefs, organizational structures, and leadership practices that support improvisation. We will draw primarily upon the model from Barrett (2012) that focuses on the how the nature of jazz improvisation and the factors that support improvisation can be transferred to leadership activities. This falls in the tradition of others who draw upon arts-based metaphors, including jazz music and theatrical improvisation, to suggest insights for leadership and ways of organizing. Since this is a book devoted to individual transformation as well as organizational transformation, we will also touch on the topic of how improvisation is a developmental project and explore the potential for improvisation to lead to personal transformation. We will attempt to move back and forth between both themes – organizational and personal transformation. Ultimately the two topics are not separate. Any significant organizational transformation begins with an improvisation. And any meaningful improvisatory move by a person is potentially a moment of self-discovery and an identity-shaping event

Evidence for intense REE scavenging at cold seeps from the Niger Delta margin

International audienceFor many trace elements, continental margins are the location of intense exchange processes between sediment and seawater, which control their distribution in the water column, but have yet to be fully understood. In this study, we have investigated the impact of fluid seepage at cold seeps on the marine cycle of neodymium. We determined dissolved and total dissolvable (TD) concentrations for REE and well-established tracers of fluid seepage (CH4, TDFe, TDMn), and Nd isotopic compositions in seawater samples collected above cold seeps and a reference site (i.e. away from any fluid venting area) from the Niger Delta margin. We also analyzed cold seep authigenic phases and various core-top sediment fractions (pore water, detrital component, easily leachable phases, uncleaned foraminifera) recovered near the hydrocast stations. Methane, TDFe and TDMn concentrations clearly indicate active fluid venting at the studied seeps, with plumes rising up to about 100 m above the seafloor. Depth profiles show pronounced REE enrichments in the non-filtered samples (TD concentrations) within plumes, whereas filtered samples (dissolved concentrations) exhibit slight REE depletion in plumes relative to the overlying water column and display typical seawater REE patterns. These results suggest that the net flux of REE emitted into seawater at cold seeps is controlled by the presence of particulate phases, most probably Fe-Mn oxyhydroxides associated to resuspended sediments. At the reference site, however, our data reveal significant enrichment for dissolved REE in bottom waters, that clearly relates to diffusive benthic fluxes from surface sediments. Neodymium isotopic ratios measured in the water column range from εNd ~−15.7 to − 10.4. Evidence that the εNd values for Antarctic Intermediate waters (AAIW) differed from those reported for the same water mass at open ocean settings shows that sediment/water interactions take place in the Gulf of Guinea. At each site, however, the bottom water εNd signature generally differs from that for cold seep minerals, easily leachable sediment phases, and detrital fractions from local sediments, ruling out the possibility that seepage of methane-rich fluids and sediment dissolution act as a substantial source of dissolved Nd to seawater in the Gulf of Guinea. Taken together, our data hence suggest that co-precipitation of Fe-Mn oxyhydroxide phases in sub-surface sediments leads to quantitative scavenging of dissolved REE at cold seeps, preventing their emission into bottom waters. Most probably, it is likely that diffusion from suboxic surface sediments dominates the exchange processes affecting the marine Nd cycle at the Niger Delta margin

Quantifying garnet-melt trace element partitioning using lattice-strain theory: New crystal-chemical and thermodynamic constraints

Many geochemical models of major igneous differentiation events on the Earth, the Moon, and Mars invoke the presence of garnet or its high-pressure majoritic equivalent as a residual phase, based on its ability to fractionate critical trace element pairs (Lu/Hf, U/Th, heavy REE/light REE). As a result, quantitative descriptions of mid-ocean ridge and hot spot magmatism, and lunar, martian, and terrestrial magma oceans require knowledge of garnet-melt partition coefficients over a wide range of conditions. In this contribution, we present new crystal-chemical and thermodynamic constraints on the partitioning of rare earth elements (REE), Y and Sc between garnet and anhydrous silicate melt as a function of pressure (P), temperature (T), and composition (X). Our approach is based on the interpretation of experimentally determined values of partition coefficients D using lattice-strain theory. In this and a companion paper (Draper and van Westrenen this issue) we derive new predictive equations for the ideal ionic radius of the dodecahedral garnet X-site,

Seismic and geochemical evidence for large-scale mantle upwelling beneath the eastern Atlantic and western and central Europe

Seismic tomography and the isotope geochemistry of Cenozoic volcanic rocks suggest the existence of a large, sheet-like region of upwelling in the upper mantle which extends from the eastern Atlantic Ocean to central Europe and the western Mediterranean. A belt of extension and rifting in the latter two areas appears to lie above the intersection of the centre of the upwelling region with the base of the lithosphere. Lead, strontium and neodymium isotope data for all three regions converge on a restricted composition, inferred to be that of the upwelling mantle