Supersingular isogeny graphs and endomorphism rings:reductions and solutions

In this paper, we study several related computational problems for supersingular elliptic curves, their isogeny graphs, and their endomorphism rings. We prove reductions between the problem of path finding in the -isogeny graph, computing maximal orders isomorphic to the endomorphism ring of a supersingular elliptic curve, and computing the endomorphism ring itself. We also give constructive versions of Deuring’s correspondence, which associates to a maximal order in a certain quaternion algebra an isomorphism class of supersingular elliptic curves. The reductions are based on heuristics regarding the distribution of norms of elements in quaternion algebras. We show that conjugacy classes of maximal orders have a representative of polynomial size, and we define a way to represent endomorphism ring generators in a way that allows for efficient evaluation at points on the curve. We relate these problems to the security of the Charles-Goren-Lauter hash function. We provide a collision attack for special but natural parameters of the hash function and prove that for general parameters its preimage and collision resistance are also equivalent to the endomorphism ring computation problem.SCOPUS: cp.kinfo:eu-repo/semantics/published37th Annual International Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2018; Tel Aviv; Israel; 29 April 2018 through 3 May 2018ISBN: 978-331978371-0Volume Editors: Nielsen J.B.Rijmen V.Publisher: Springer Verla

Shell evolution and the N=34 “magic number”

Measurements of de–excitation gamma–rays in coincidence with target-like residues produced in deep inelastic transfer reactions of $^{238}$U on a $^{48}$Ca target at an energy near the Coulomb barrier are presented. A systematic analysis of the measured low lying states in the odd and even neutron-rich Ca isotopes shows the absence of a predicted shell closure at N = 34 in neutron-rich calcium isotopes

Catalytic steam reforming of methane over La0.8Sr0.2CrO3 based Ru catalysts

La0.8Sr0.2CrO3 based Ru catalysts were studied as potential new anodic materials for Solid Oxide Fuel Cells directly fed with methane and operating at intermediate temperature under water deficient conditions. Two kinds of materials very close in composition were obtained following two different preparation procedures. Catalyst samples were characterized by physicochemical methods (XRD, SEM, BET and Chemical Analysis) and studied in methane steam reforming under water deficient conditions. Carbon formation during catalytic testing was studied by temperature programmed oxidation (TPO). Both types of catalysts were found very active and resistant to carbon formation. The unusual oscillatory behavior of the catalytic activity observed for one type of catalyst was discussed. © 2007 Elsevier B.V. All rights reserved

Gene expression plasticity and frontloading promote thermotolerance in Pocillopora corals

ABSTRACT Ecosystems worldwide are suffering from climate change. Coral reef ecosystems are globally threatened by increasing sea surface temperatures. However, gene expression plasticity provides the potential for organisms to respond rapidly and effectively to environmental changes, and would be favored in variable environments. In this study, we investigated the thermal stress response in Pocillopora coral colonies from two contrasting environments by exposing them to heat stress. We compared the physiological state, bacterial and Symbionaceae communities (using 16S and ITS2 metabarcoding), and gene expression levels (using RNA-Seq) between control conditions and heat stress (the temperature just below the first signs of compromised health). Colonies from both thermal regimes remained apparently normal and presented open and colored polyps during heat stress, with no change in bacterial and Symbionaceae community composition. In contrast, they differed in their transcriptomic responses. The colonies from Oman displayed a more plastic transcriptome, but some genes had a higher basal expression level (frontloading) compared to the less thermotolerant colonies from New Caledonia. In terms of biological functions, we observed an increase in the expression of stress response genes (including induction of tumor necrosis factor receptors, heat shock proteins, and detoxification of reactive oxygen species), together with a decrease in the expression of genes involved in morpho-anatomical functions. Gene regulation (transcription factors, mobile elements, histone modifications and DNA methylation) appeared to be overrepresented in the Oman colonies, indicating possible epigenetic regulation. These results show that transcriptomic plasticity and frontloading can be co-occurring processes in corals confronted to highly variable thermal regimes

MUST2: A new generation array for direct reaction studies

NESTER SEP ACCWe have developed a new telescope array, dedicated to the study of direct reactions of exotic nuclei on light targets in inverse kinematics. This device, called MUST2, is briefly described, and the results of the first tests performed with an alpha source and Ni beams at 10 and 75 MeV/u on a CDH target are presented