On the effect of image denoising on galaxy shape measurements

Weak gravitational lensing is a very sensitive way of measuring cosmological parameters, including dark energy, and of testing current theories of gravitation. In practice, this requires exquisite measurement of the shapes of billions of galaxies over large areas of the sky, as may be obtained with the EUCLID and WFIRST satellites. For a given survey depth, applying image denoising to the data both improves the accuracy of the shape measurements and increases the number density of galaxies with a measurable shape. We perform simple tests of three different denoising techniques, using synthetic data. We propose a new and simple denoising method, based on wavelet decomposition of the data and a Wiener filtering of the resulting wavelet coefficients. When applied to the GREAT08 challenge dataset, this technique allows us to improve the quality factor of the measurement (Q; GREAT08 definition), by up to a factor of two. We demonstrate that the typical pixel size of the EUCLID optical channel will allow us to use image denoising.Comment: Accepted for publication in A&A. 8 pages, 5 figure

Multiple bond 13C-13C spin-spin coupling provides complementary information in a 13C NMR isotopomer analysis of glutamate

Most 13C nuclear magnetic resonance (NMR) isotopomer analyses relate a metabolic index of interest to populations of 13C isotopomers as reported by one-bond 13C-13C spin-spin couplings. Metabolic conditions that produce highly enriched citric acid cycle intermediates often lead to 13C NMR spectra of metabolites such as glutamate that show extra multiplets due to long-range couplings. It can be demonstrated from 13C NMR spectra of hearts perfused with mixtures of acetate plus propionate that multiplets in glutamate C2 arising from 3J25 coupling provide a direct readout of acetyl-CoA fractional enrichment (FC1 and FC3), while multiplets in glutamate C5 arising from 2J35 and 3J25 couplings quantitatively reflect enrichment of the anaplerotic substrate. Magn Reson Med 42:197-200, 1999. © 1999 Wiley-Liss, Inc

mRNA Translation: Fungal Variations on a Eukaryotic Theme

The accurate transfer of information from a nucleotide-based code to a protein-based one is at the heart of all life processes. The actual information transfer occurs during protein synthesis or translation, and is catalysed by ribosomes, supported by a large host of additional protein activities—the translation factors. This chapter reviews how the different eukaryotic initiation, elongation and termination factors assist the ribosome in establishing appropriate contacts with mRNAs during translation initiation, decode the genetic code during translation elongation, and finally release the newly made polypeptide and reuse the ribosomes during the termination and recycling phases

Synonymous codons, ribosome speed, and eukaryotic gene expression regulation

Quantitative control of gene expression occurs at multiple levels, including the level of translation. Within the overall process of translation, most identified regulatory processes impinge on the initiation phase. However, recent studies have revealed that the elongation phase can also regulate translation if elongation and initiation occur with specific, not mutually compatible rate parameters. Translation elongation then limits the overall amount of protein that can be made from an mRNA. Several recently discovered control mechanisms of biological pathways are based on such elongation control. Here, we review the molecular mechanisms that determine ribosome speed in eukaryotic organisms, and discuss under which conditions ribosome speed can become the controlling parameter of gene expression levels