4,540 research outputs found
Model-based scenarios of Mediterranean droughts
International audienceThis study examines the change in current 100-year hydrological drought frequencies in the Mediterranean in comparison to the 2070s as simulated by the global model WaterGAP. The analysis considers socio-economic and climate changes as indicated by the IPCC scenarios A2 and B2 and the global general circulation model ECHAM4. Under these conditions today's 100-year drought is estimated to occur 10 times more frequently in the future over a large part of the Northern Mediterranean while in North Africa, today's 100-year drought will occur less frequently. Water abstractions are shown to play a minor role in comparison to the impact of climate change, but can intensify the situation
Intellectual property as complex innovation projects component
The materials presented the possibilities development of intellectual property complex innovation projects modern highly effective science-based problems of improving the use of wastes of different industries on a complex enterprise that can provide all its energy needs alone. Some features of the possibilities of solving evidence-based problems of development of mechanisms for identifying syner-gistic processes, their scientific justification improving the use of wastes of different industries on a complex enterprise. The problem of wastes utilization and recycling is present as complex synergetic processes research and analysis of energy- and resource saving process-es for treatment of polymer wastes of various origin. The research focused on the study of issues such as the development of models of waste-modifying polymer. The investigation are focused in researching such problems as selection of scientific based methods of wastes to be utilized or recycled; the development of appropriated process flow sheets and choice of modifications additives and equipment for polymers waste recycling. The choice of appropriate plants with selected energy resources is very important for projects realization
The effect of Coulombic friction on spatial displacement statistics
The phenomenon of Coulombic friction enters the stochastic description of dry
friction between two solids and the statistic characterization of vibrating
granular media. Here we analyze the corresponding Fokker-Planck equation
including both velocity and spatial components, exhibiting a formal connection
to a quantum mechanical harmonic oscillator in the presence of a delta
potential. Numerical solutions for the resulting spatial displacement
statistics show a crossover from exponential to Gaussian displacement
statistics. We identify a transient intermediate regime that exhibits
multiscaling properties arising from the contribution of Coulombic friction.
The possible role of these effects during observations in diffusion experiments
is shortly discussed.Comment: 11 pages, 9 figure
Electrical and mechanical behaviour of metal thin films with deformation-induced cracks predicted by computational homogenisation
Motivated by advances in flexible electronic technologies and by the endeavour to develop non-destructive testing methods, this article analyses the capability of computational multiscale formulations to predict the influence of microscale cracks on effective macroscopic electrical and mechanical material properties. To this end, thin metal films under mechanical load are experimentally analysed by using in-situ confocal laser scanning microscopy (CLSM) and in-situ four point probe resistance measurements. Image processing techniques are then used to generate representative volume elements from the laser intensity images. These discrete representations of the crack pattern at the microscale serve as the basis for the calculation of effective macroscopic electrical conductivity and mechanical stiffness tensors by means of computational homogenisation approaches. A comparison of simulation results with experimental electrical resistance measurements and a detailed study of fundamental numerical properties demonstrates the applicability of the proposed approach. In particular, the (numerical) errors that are induced by the representative volume element size and by the finite element discretisation are studied, and the influence of the filter that is used in the generation process of the representative volume element is analysed
Membrane penetration and trapping of an active particle
The interaction between nano- or micro-sized particles and cell membranes is
of crucial importance in many biological and biomedical applications such as
drug and gene delivery to cells and tissues. During their cellular uptake, the
particles can pass through cell membranes via passive endocytosis or by active
penetration to reach a target cellular compartment or organelle. In this
manuscript, we develop a simple model to describe the interaction of a
self-driven spherical particle (moving through an effective constant active
force) with a minimal membrane system, allowing for both penetration and
trapping. We numerically calculate the state diagram of this system, the
membrane shape, and its dynamics. In this context, we show that the active
particle may either get trapped near the membrane or penetrates through it,
where the membrane can either be permanently destroyed or recover its initial
shape by self-healing. Additionally, we systematically derive a continuum
description allowing to accurately predict most of our results analytically.
This analytical theory helps identifying the generic aspects of our model,
suggesting that most of its ingredients should apply to a broad range of
membranes, from simple model systems composed of magnetic microparticles to
lipid bilayers. Our results might be useful to predict mechanical properties of
synthetic minimal membranes.Comment: 16 pages, 6 figures. Revised manuscript resubmitted to J. Chem. Phy
Towards an analytical description of active microswimmers in clean and in surfactant-covered drops
Geometric confinements are frequently encountered in the biological world and
strongly affect the stability, topology, and transport properties of active
suspensions in viscous flow. Based on a far-field analytical model, the
low-Reynolds-number locomotion of a self-propelled microswimmer moving inside a
clean viscous drop or a drop covered with a homogeneously distributed
surfactant, is theoretically examined. The interfacial viscous stresses induced
by the surfactant are described by the well-established Boussinesq-Scriven
constitutive rheological model. Moreover, the active agent is represented by a
force dipole and the resulting fluid-mediated hydrodynamic couplings between
the swimmer and the confining drop are investigated. We find that the presence
of the surfactant significantly alters the dynamics of the encapsulated swimmer
by enhancing its reorientation. Exact solutions for the velocity images for the
Stokeslet and dipolar flow singularities inside the drop are introduced and
expressed in terms of infinite series of harmonic components. Our results offer
useful insights into guiding principles for the control of confined active
matter systems and support the objective of utilizing synthetic microswimmers
to drive drops for targeted drug delivery applications.Comment: 19 pages, 7 figures. Regular article contributed to the Topical Issue
of the European Physical Journal E entitled "Physics of Motile Active Matter"
edited by Gerhard Gompper, Clemens Bechinger, Holger Stark, and Roland G.
Winkle
Focusing by blocking: repeatedly generating central density peaks in self-propelled particle systems by exploiting diffusive processes
Over the past few years the displacement statistics of self-propelled
particles has been intensely studied, revealing their long-time diffusive
behavior. Here, we demonstrate that a concerted combination of boundary
conditions and switching on and off the self-propelling drive can generate and
afterwards arbitrarily often restore a non-stationary centered peak in their
spatial distribution. This corresponds to a partial reversibility of their
statistical behavior, in opposition to the above-mentioned long-time diffusive
nature. Interestingly, it is a diffusive process that mediates and makes
possible this procedure. It should be straightforward to verify our predictions
in a real experimental system.Comment: 6 pages, 6 figure
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