A three-dimensional wavelet based multifractal method : about the need of revisiting the multifractal description of turbulence dissipation data

We generalize the wavelet transform modulus maxima (WTMM) method to multifractal analysis of 3D random fields. This method is calibrated on synthetic 3D monofractal fractional Brownian fields and on 3D multifractal singular cascade measures as well as their random function counterpart obtained by fractional integration. Then we apply the 3D WTMM method to the dissipation field issue from 3D isotropic turbulence simulations. We comment on the need to revisiting previous box-counting analysis which have failed to estimate correctly the corresponding multifractal spectra because of their intrinsic inability to master non-conservative singular cascade measures.Comment: 5 pages, 3figures, submitted to Phys. Rev. Let

Emergence of log-normal type distributions in avalanche processes in living systems : a network model

Funding We acknowledge financial support from the Agence Nationale de la Recherche (ANR grant number ANR-18-CE45-0012-01) and from the French Research Minister (MESRI) for SP. PhD funding. Acknowledgments We are very grateful for the participants of the second ISINP meeting at Lake Como for stimulating exchanges about our talk. We are thanful to P. Argoul, A. Guillet, E. Hartè, L. Delmarre for fruitful discussions. SP wishes to thank T. Matteuzzi for his inspiring considerations. We are indebted to Erika Polizzi for her graphical help.Peer reviewedPublisher PD

Power-law and log-normal avalanche size statistics in random growth processes

ACKNOWLEDGMENTS We thank J.P. Bouchaud for constructive comments. We acknowledge financial support from the Agence Nationale de la Recherche (ANR grant number ANR-18- CE45-0012-01) and from the French Research Ministry (MESR) (contract No. 2017-SG-D-09) and from ENS Lyon for SP PhD funding. FJPR acknowledges financial support from the Carnegie Trust.Peer reviewedPostprin

Structural organization of human replication timing domains

AbstractRecent analysis of genome-wide epigenetic modification data, mean replication timing (MRT) profiles and chromosome conformation data in mammals have provided increasing evidence that flexibility in replication origin usage is regulated locally by the epigenetic landscape and over larger genomic distances by the 3D chromatin architecture. Here, we review the recent results establishing some link between replication domains and chromatin structural domains in pluripotent and various differentiated cell types in human. We reconcile the originally proposed dichotomic picture of early and late constant timing regions that replicate by multiple rather synchronous origins in separated nuclear compartments of open and closed chromatins, with the U-shaped MRT domains bordered by “master” replication origins specified by a localized (∼200–300kb) zone of open and transcriptionally active chromatin from which a replication wave likely initiates and propagates toward the domain center via a cascade of origin firing. We discuss the relationships between these MRT domains, topologically associated domains and lamina-associated domains. This review sheds a new light on the epigenetically regulated global chromatin reorganization that underlies the loss of pluripotency and the determination of differentiation properties

Automated Detection of Coronal Loops using a Wavelet Transform Modulus Maxima Method

We propose and test a wavelet transform modulus maxima method for the au- tomated detection and extraction of coronal loops in extreme ultraviolet images of the solar corona. This method decomposes an image into a number of size scales and tracks enhanced power along each ridge corresponding to a coronal loop at each scale. We compare the results across scales and suggest the optimum set of parameters to maximise completeness while minimising detection of noise. For a test coronal image, we compare the global statistics (e.g., number of loops at each length) to previous automated coronal-loop detection algorithms

Analysis of fine-scale mammalian evolutionary breakpoints provides new insight into their relation to genome organisation

<p>Abstract</p> <p>Background</p> <p>The Intergenic Breakage Model, which is the current model of structural genome evolution, considers that evolutionary rearrangement breakages happen with a uniform propensity along the genome but are selected against in genes, their regulatory regions and in-between. However, a growing body of evidence shows that there exists regions along mammalian genomes that present a high susceptibility to breakage. We reconsidered this question taking advantage of a recently published methodology for the precise detection of rearrangement breakpoints based on pairwise genome comparisons.</p> <p>Results</p> <p>We applied this methodology between the genome of human and those of five sequenced eutherian mammals which allowed us to delineate evolutionary breakpoint regions along the human genome with a finer resolution (median size 26.6 kb) than obtained before. We investigated the distribution of these breakpoints with respect to genome organisation into domains of different activity. In agreement with the Intergenic Breakage Model, we observed that breakpoints are under-represented in genes. Surprisingly however, the density of breakpoints in small intergenes (1 per Mb) appears significantly higher than in gene deserts (0.1 per Mb).</p> <p>More generally, we found a heterogeneous distribution of breakpoints that follows the organisation of the genome into isochores (breakpoints are more frequent in GC-rich regions). We then discuss the hypothesis that regions with an enhanced susceptibility to breakage correspond to regions of high transcriptional activity and replication initiation.</p> <p>Conclusion</p> <p>We propose a model to describe the heterogeneous distribution of evolutionary breakpoints along human chromosomes that combines natural selection and a mutational bias linked to local open chromatin state.</p

Wavelet-based multifractal analysis of dynamic infrared thermograms to assist in early breast cancer diagnosis

Breast cancer is the most common type of cancer among women and despite recent advances in the medical field, there are still some inherent limitations in the currently used screening techniques. The radiological interpretation of screening X-ray mammograms often leads to over-diagnosis and, as a consequence, to unnecessary traumatic and painful biopsies. Here we propose a computer-aided multifractal analysis of dynamic infrared (IR) imaging as an efficient method for identifying women with risk of breast cancer. Using a wavelet-based multi-scale method to analyze the temporal fluctuations of breast skin temperature collected from a panel of patients with diagnosed breast cancer and some female volunteers with healthy breasts, we show that the multifractal complexity of temperature fluctuations observed in healthy breasts is lost in mammary glands with malignant tumor. Besides potential clinical impact, these results open new perspectives in the investigation of physiological changes that may precede anatomical alterations in breast cancer development

La transformation en ondelettes continue : un microscope mathématique adapté à l'étude des propriétés d'invariance d'échelle et de corrélations à longue portée des séquences d'ADN

Depuis le début des années 90, l'intérêt des mathématiciens, physiciens et informaticiens pour l'analyse statistique des séquences d'ADN n'a pas cessé de croître. En effet, les immenses progrès de la biologie moléculaire et les grands projets de séquençage ont révélé l'extraordinaire complexité des génomes. Afin de mieux comprendre l'organisation et l'évolution des génomes, il est apparu nécessaire d'introduire de nouveaux concepts et de nouvelles techniques d'analyse du signal. Ainsi la possibilité que les séquences d'ADN présentent des propriétés d'invariance d'échelle associées à l'existence de corrélations à longue portée (CLP) a été le sujet d'une longue controverse. La raison principale de ce malentendu est le caractère non stationnaire des séquences d'ADN résultant de l'hétérogénéité de composition des génomes. Cette observation nous a conduit à proposer l'utilisation de la transformation en ondelettes continue (TO) comme outil naturel d'analyse des séquences d'ADN : par un choix adéquat de l'ondelette analysatrice, on peut s'affranchir de la "structure mosaïque" de ces séquences et quantifier l'existence de CLP associées à des propriétés d'invariance d'échelle monofractales. L'exploration de séquences d'ADN du génome humain sous l'optique du microscope TO, nous a permis de démontrer l'existence de CLP dans les séquences exoniques (codantes pour les protéines) comme dans les séquences introniques (non codantes), remettant par là en cause les différentes interprétations de ces corrélations à l'aide de modèles de dynamique évolutive (plasticité) des génomes. En profitant de la disponibilité de génomes complets (levure, E. coli,...) et en utilisant différentes tables expérimentales associant des di- ou tri- nucléotides à des grandeurs de nature structurelle (courbure, flexibilité), nous avons montré récemment qu'il est possible d'extraire des séquences d'ADN des informations sur l'organisation spatiale et dynamique de la double hélice dans les cellules via l'interaction avec certaines protéines de structure telles que les histones pour la formation du nucléosome eucaryote. En particulier, l'existence et la nature des CLP jusqu'à des distances de l'ordre de 3 104 nucléotides dans certains profils de courbure et/ou de flexibilité locales permettent de diagnostiquer la présence de nucléosomes dans les génomes étudiés. L'observation de certaines CLP dans tous les organismes eucaryotes ainsi que dans les organismes des deux autres règnes (eubactéries et archaeabactéries) suggère fortement que ces corrélations pourraient être essentielles aux phénomènes de condensation-décondensation de la chromatine en relation avec les processus de réplication, transcription et division cellulaire