FM-track: a fiducial marker tracking software for studying cell mechanics in a three-dimensional environment

Tracking the deformation of fiducial markers in the vicinity of living cells embedded in compliant synthetic or biological gels is a powerful means to study cell mechanics and mechanobiology in three-dimensional environments. However, current approaches to track and quantify three-dimensional (3D) fiducial marker displacements remain ad-hoc, can be difficult to implement, and may not produce reliable results. Herein, we present a compact software package entitled “FM-Track,” written in the popular Python language, to facilitate feature-based particle tracking tailored for 3D cell micromechanical environment studies. FM-Track contains functions for pre-processing images, running fiducial marker tracking, and post-processing and visualization. FM-Track can thus aid the study of cellular mechanics and mechanobiology by providing an extensible software platform to more reliably extract complex local 3D cell contractile information in transparent compliant gel systems.https://www.sciencedirect.com/science/article/pii/S2352711019303474Published versio

Automated Determination of Stellar Parameters from Simulated Dispersed Images for DIVA

We have assessed how well stellar parameters (T_eff, logg and [Fe/H]) can be retrieved from low-resolution dispersed images to be obtained by the DIVA satellite. Although DIVA is primarily an all-sky astrometric mission, it will also obtain spectrophotometric information for about 13 million stars (operational limiting magnitude V ~ 13.5 mag). Constructional studies foresee a grating system yielding a dispersion of ~200nm/mm on the focal plane (first spectral order). For astrometric reasons there will be no cross dispersion which results in the overlapping of the first to third diffraction orders. The one-dimensional, position related intensity function is called a DISPI (DISPersed Intensity). We simulated DISPIS from synthetic spectra (...) for a limited range of metallicites i.e. our results are for [Fe/H] in the range -0.3 to 1 dex. We show that there is no need to deconvolve these low resolution signals in order to obtain basic stellar parameters. Using neural network methods and by including simulated data of DIVA's UV telescope, we can determine T_eff to an average accuracy of about 2% for DISPIS from stars with 2000 K < T_eff < 20000 K and visual magnitudes of V=13 mag (end of mission data). logg can be determined for all temperatures with an accuracy better than 0.25 dex for magnitudes brighter than V=12 mag. For low temperature stars with 2000 K < T_eff < 5000 K and for metallicities in the range -0.3 to +1 dex a determination of [Fe/H] is possible (to better than 0.2 dex) for these magnitudes. Additionally we examined the effects of extinction E(B-V) on DISPIS and found that it can be determined to better than 0.07 mag for magnitudes brighter than V=14 mag if the UV information is included.Comment: 12 pages, 8 figures, Accepted for publication in A&

Self-consistent calculations of the electric giant dipole resonances in light and heavy mass nuclei

While bulk properties of stable nuclei are successfully reproduced by mean-field theories employing effective interactions, the dependence of the centroid energy of the electric giant dipole resonance on the nucleon number A is not. This problem is cured by considering many-particle correlations beyond mean-field theory, which we do within the "Quasiparticle Time Blocking Approximation". The electric giant dipole resonances in $^{16}$O, $^{40}$Ca, and $^{208}$Pb are calculated using two new Skyrme interactions.Comment: 4 pages, 4 figure

The Łojasiewicz exponent over a field of arbitrary characteristic

Let K be an algebraically closed field and let K((XQ)) denote the field of generalized series with coefficients in K. We propose definitions of the local Łojasiewicz exponent of F = ( f1, . . . , fm) ∈ K[[X, Y ]]m as well as of the Łojasiewicz exponent at infinity of F = ( f1, . . . , fm) ∈ K[X, Y ]m, which generalize the familiar case of K = C and F ∈ C{X, Y }m (resp. F ∈ C[X, Y ]m), see Cha˛dzy´nski and Krasi´nski (In: Singularities, 1988; In: Singularities, 1988; Ann Polon Math 67(3):297–301, 1997; Ann Polon Math 67(2):191–197, 1997), and prove some basic properties of such numbers. Namely, we show that in both cases the exponent is attained on a parametrization of a component of F (Theorems 6 and 7), thus being a rational number. To this end, we define the notion of the Łojasiewicz pseudoexponent of F ∈ (K((XQ))[Y ])m for which we give a description of all the generalized series that extract the pseudoexponent, in terms of their jets. In particular, we show that there exist only finitely many jets of generalized series giving the pseudoexponent of F (Theorem 5). The main tool in the proofs is the algebraic version of Newton’s Polygon Method. The results are illustrated with some explicit examples

Asteroseismology of exoplanets host stars: the special case of ι\iota Horologii (HD17051)

{This paper presents detailed analysis and modelisation of the star HD17051 (alias $\iota$ Hor), which appears as a specially interesting case among exoplanet host stars. As most of these stars, $\iota$ Hor presents a metallicity excess which has been measured by various observers who give different results, ranging from [Fe/H] = 0.11 to 0.26, associated with different atmospheric parameters. Meanwhile the luminosity of the star may be determined owing to Hipparcos parallax. Although in the southern hemisphere, this star belongs to the Hyades stream and its external parameters show that it could even be one of the Hyades stars ejected during cluster formation. The aim of this work was to gather and analyse our present knowledge on this star and to prepare seismic tests for future observations with the HARPS spectrometer (planned for November 2006).} {We have computed evolutionary tracks with various metallicities, in the two frameworks of primordial overmetallicity and accretion. We have concentrated on models inside the error boxes given by the various observers in the log g - log T$_{eff}$ diagram. We then computed the adiabatic oscillation frequencies of these models to prepare future observations.} {The detailed analysis of $\iota$ Hor presented in this paper already allowed to constrain its external parameters, mass and age. Some values given in the literature could be rejected as inconsistent with the overall analysis. We found that a model computed with the Hyades parameters (age, metallicity) was clearly acceptable, but other ones were possible too. We are confident that observations with HARPS will allow for a clear conclusion about this star and that it will bring important new light on the physics of exoplanet host stars.}Comment: to be published in Astronomy and Astrophysic