A note on patch-based low-rank minimization for fast image denoising

Patch-based low-rank minimization for image processing attracts much attention in recent years. The minimization of the matrix rank coupled with the Frobenius norm data fidelity can be solved by the hard thresholding filter with principle component analysis (PCA) or singular value decomposition (SVD). Based on this idea, we propose a patch-based low-rank minimization method for image denoising. The main denoising process is stated in three equivalent way: PCA, SVD and low-rank minimization. Compared to recent patch-based sparse representation methods, experiments demonstrate that the proposed method is rather rapid, and it is effective for a variety of natural grayscale images and color images, especially for texture parts in images. Further improvements of this method are also given. In addition, due to the simplicity of this method, we could provide an explanation of the choice of the threshold parameter, estimation of PSNR values, and give other insights into this method.Comment: 4pages (two columns

First direct observation of a torsional Alfvén oscillation at coronal heights

Context. Torsional Alfvén waves are promising candidates for the transport of energy across different layers of the solar atmosphere. They have been predicted theoretically for decades. Previous detections of Alfvén waves so far have however mostly relied on indirect signatures. Aims. We present the first direct observational evidence of a fully resolved torsional Alfvén oscillation of a large-scale structure occurring at coronal heights. Methods. We analysed IRIS imaging and spectral observation of a surge resulting from magnetic reconnection between active region prominence threads and surrounding magnetic field lines. Results. The IRIS spectral data provide clear evidence of an oscillation in the line-of-sight velocity with a 180° phase difference between the oscillation signatures at opposite edges of the surge flux tube. This together with an alternating tilt in the Si IV and Mg II k spectra across the flux tube and the trajectories traced by the individual threads of the surge material provide clear evidence of torsional oscillation of the flux tube. Conclusions. Our observation shows that magnetic reconnection leads to the generation of large-scale torsional Alfvén waves

PPARs and RXRs in Male and Female Fertility and Reproduction

International audienc

The consequences of wax-resin linings for the present appearance and conservation of seventeenth century Netherlandish paintings on canvas

Most of the canvas paintings in Dutch collections have been wax-resin lined. This restoration method, used by conservators from the mid-nineteenth century onwards, is known to darken paintings. Many Netherlandish seventeenth century paintings were painted leaving locally the ground visible, to be used as a mid-tone. A colour change of the ground imparted by lining would therefore alter the tonal balance of the paintings. Furthermore, since colour change implies a modification of the physical characteristics of the paint film, it is important for conservators to be able to recognize such alteration. This PhD investigated the materials from the ground layers of a range of seventeenth century Netherlandish paintings in order to create ground reconstructions that provided the means to compare colour change on lining. The colour measurements showed that after treatment, the ground reconstructions became darker and cooler in hue. Furthermore, the study of the measurements indicated that the extent of change depended on the layer thickness, the type of binding medium as well as on the nature and proportion of inorganic components present. The hiding power of the grounds was also found to be a key factor. The research enables conservators to predict the likelihood that paintings have been altered by wax-resin lining. It also brings new insight for recognizing and understanding visual changes caused by this treatment and provides new evidence to reconsider the original appearance of paintings

Ecologie humaine et médecine tropicale

Si la démarche médicale tient actuellement davantage compte des facteurs culturels et des comportements, elle néglige encore fréquemment deux notions fondamentales qui caractérisent, sur le plan biologique, l'espèce humaine, pourtant remarquable par son polymorphisme: plasticité vis-à-vis de l'environnement, et variabilité dans le temps et dans l'espace. L'anthropologie physique, régénérée par l'apport de la génétique des populations et le raisonnement écologique à causalité non linéaire, a un rôle important à jouer pour mieux explorer l'adéquation entre l'homme et le milieu (tropical ou non) et en imprégner le regard médical encore très normatif. L'article discute la contribution d'une écobiologie humaine aux rapports entre agent pathogène, hôte, environnement et filtres culturels. Les différents champs de recherche possibles sont passés en revue