Influence of the size of the intruder on the reorganization of a 2D granular medium

Granular Matter - Compressed frictional granular matter cannot flow without dilation. Upon forced shearing to generate flow, the amount of dilation may depend on the initial preparation and a host...     

Logical foundations of multilevel databases

In this paper, we propose a formal model for multilevel databases. This model aims at being a generic model, that is it can be interpreted for any kind of database (relational, object-oriented …). Our model has three layers. The first layer corresponds to a model for a non-protected database. The second layer corresponds to a model for a multilevel database. In this second layer, we propose a list of theorems that must be respected in order to build a secure multilevel database. We also propose a new solution to manage cover stories without using the ambiguous technique of polyinstantiation. The third layer corresponds to a model for a MultiView database, that is, a database that provides at each security level a consistent view of the multilevel database. Finally, as an illustration, we interpret our 3-layer model in the case of an object-oriented database.     

Copper‐Catalyzed Decarboxylation of Aromatic Carboxylic Acids: En Route to Milder Reaction Conditions

The copper‐catalyzed decarboxylation of carboxylic aromatic acids has been advantageously achieved by using aliphatic amines like tetramethylethylenediamine (TMEDA) or hexamethylenetetraamine (HMTA) as ligands instead of the aromatic heterocyclic amines (quinoline, phenanthroline) used until now. The improvement is significant since the reaction can be performed at a lower temperature (ca. 50 °C less) and the reaction time is clearly shorter (15 min instead of 12 to 24 h).     

The carmaphycins: new proteasome inhibitors exhibiting an α,β-epoxyketone warhead from a marine cyanobacterium

Two new peptidic proteasome inhibitors were isolated as trace components from a Curaçao collection of the marine cyanobacterium Symploca sp. Carmaphycin A ( 1 ) and carmaphycin B ( 2 ) feature a leucine‐derived α,β‐epoxyketone warhead directly connected to either methionine sulfoxide or methionine sulfone. Their structures were elucidated on the basis of extensive NMR and MS analyses and confirmed by total synthesis, which in turn provided more material for further biological evaluations. Pure carmaphycins A and B were found to inhibit the β5 subunit (chymotrypsin‐like activity) of the S. cerevisiae 20S proteasome in the low nanomolar range. Additionally, they exhibited strong cytotoxicity to lung and colon cancer cell lines, as well as exquisite antiproliferative effects in the NCI60 cell‐line panel. These assay results as well as initial structural biology studies suggest a distinctive binding mode for these new inhibitors.     

Serre’s reduction of linear partial differential systems with holonomic adjoints

Given a linear functional system (e.g., an ordinary/partial differential system, a differential time-delay system, a difference system), Serre’s reduction aims at finding an equivalent linear functional system which contains fewer equations and fewer unknowns. The purpose of this paper is to study Serre’s reduction of underdetermined linear systems of partial differential equations with either polynomial, formal power series or locally convergent power series coefficients, and with holonomic adjoints in the sense of algebraic analysis. We prove that these linear partial differential systems can be defined by means of only one linear partial differential equation. In the case of polynomial coefficients, we give an algorithm to compute the corresponding equation.     

Computable processes and bisimulation equivalence

A process is calledcomputable if it can be modelled by a transition system that has a recursive structure—implying finite branching. The equivalence relation between transition systems considered is strong bisimulation equivalence. The transition systems studied in this paper can be associated to processes specified in common specification languages such as CCS, LOTOS, ACP and PSF. As a means for defining transition systems up to bisimulation equivalence, the specification languageCRL is used. Two simple fragments of,CRL are singled out, yielding universal expressivity with respect to recursive and primitive recursive transition systems. For both these domains the following properties are classified in the arithmetical hierarchy:bisimilarity, perpetuity (both ₁ ⁰ ),regularity (having a bisimilar, finite representation, ₂ ⁰ ),acyclic regularity ( ₁ ⁰ ), anddeadlock freedom (distinguishing deadlock from successful termination, ₁ ⁰ ). Finally, it is shown that in the domain of primitive recursive transition systems over a fixed, finite label set, a genuine hierarchy in bisimilarity can be defined by the complexity of the witnessing relations, which extends r.e. bisimilarity. Hence, primitive recursive transition systems already form an interesting class.     

Machine Learning With Data Assimilation and Uncertainty Quantification for Dynamical Systems: A Review

Data assimilation (DA) and uncertainty quantification (UQ) are extensively used in analysing and reducing error propagation in high-dimensional spatial-temporal dynamics. Typical applications span from computational fluid dynamics (CFD) to geoscience and climate systems. Recently, much effort has been given in combining DA, UQ and machine learning (ML) techniques. These research efforts seek to address some critical challenges in high-dimensional dynamical systems, including but not limited to dynamical system identification, reduced order surrogate modelling, error covariance specification and model error correction. A large number of developed techniques and methodologies exhibit a broad applicability across numerous domains, resulting in the necessity for a comprehensive guide. This paper provides the first overview of state-of-the-art researches in this interdisciplinary field, covering a wide range of applications. This review is aimed at ML scientists who attempt to apply DA and UQ techniques to improve the accuracy and the interpretability of their models, but also at DA and UQ experts who intend to integrate cutting-edge ML approaches to their systems. Therefore, this article has a special focus on how ML methods can overcome the existing limits of DA and UQ, and vice versa. Some exciting perspectives of this rapidly developing research field are also discussed.