Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Fourier-analysis of Finite-element Preconditioned Collocation Schemes

This paper investigates the spectrum of the iteration operator of some finite element preconditioned Fourier collocation schemes. The first part of the paper analyses one-dimensional elliptic and hyperbolic model problems and the advection-diffusion equation. Analytical expressions of the eigenvalues are obtained with use of symbolic computation. The second part of the paper considers the set of one-dimensional differential equations resulting from Fourier analysis (in the transverse direction) of the two-dimensional Stokes problem. All results agree with previous conclusions on the numerical efficiency of finite element preconditioning schemes

Spectral Elements for Viscoelastic Flows With Change of Type

The spectral element method is used on periodic flows containing change of type of the vorticity equation. On slightly perturbed viscometric flows in a channel, the method is compared to the so-called EVSS finite element method and to analytical results when they are available. It is found that the method performs very well on all flows examined and that the computational cost is reduced compared to EVSS. The analysis of the uniform perturbed flow of a Maxwell fluid has revealed an unusual condition on the polynomial space containing the extra-stress representations. The technique is also applied to study the increase of the flow resistance in a periodically constricted tube. Results are compared with existing ones produced by means of the mixed pseudospectral-finite difference method (PCFD). Excellent agreement is found when comparing flow resistance. Explanation of the observed numerical difficulties is also investigated by inspection of the vorticity patterns corresponding to several pairs of Weissenberg and Reynolds numbers

A Fast Schur Complement Method for the Spectral Element Discretization of the Incompressible Navier-stokes Equations

The weak formulation of the incompressible Navier-Stokes equations in three space dimensions is discretized with spectral element approximations and Gauss-Lobatto-Legendre quadratures. The Uzawa algorithm is applied to decouple the Velocities from the pressure. The equation that results for the pressure is solved by an iterative method. Within each pressure iteration, a Helmholtz operator has to be inverted. This can efficiently be done by separating the equations for the interior nodes from the equations at the interfaces, according to the Schur method. Fast diagonalization techniques are applied to the interior variables of the spectral elements. Several ways to deal with the resulting interface problem are discussed. Finally, a comparison is made with a more classical method. (C) 1995 Academic Press, Inc