Is-ClusterMPP: clustering algorithm through point processes and influence space towards high-dimensional data

Advances in Data Analysis and Classification - Clustering via marked point processes and influence space, Is-ClusterMPP, is a new unsupervised clustering algorithm through adaptive MCMC sampling of...     

Formation of Amphiphilic Molecules from the Most Common Marine Polysaccharides,toward a Sustainable Alternative?

Marine polysaccharides are part of the huge seaweeds resources and present many applications for several industries. In order to widen their potential as additives or bioactive compounds, some structural modifications have been studied. Among them, simple hydrophobization reactions have been developed in order to yield to grafted polysaccharides bearing acyl-, aryl-, alkyl-, and alkenyl-groups or fatty acid chains. The resulting polymers are able to present modified physicochemical and/or biological properties of interest in the current pharmaceutical, cosmetics, or food fields. This review covers the chemical structures of the main marine polysaccharides, and then focuses on their structural modifications, and especially on hydrophobization reactions mainly esterification, acylation, alkylation, amidation, or even cross-linking reaction on native hydroxyl-, amine, or carboxylic acid functions. Finally, the question of the necessary requirement for more sustainable processes around these structural modulations of marine polysaccharides is addressed, considering the development of greener technologies applied to traditional polysaccharides.     

Relationships between molar mass and fracture properties of segmented urethane and amide copolymers modified by chemical degradation

This publication highlights the structure–property relationships in several thermoplastic elastomers (TPEs): one poly(ether-block-amide) and two thermoplastic polyurethane elastomers with ester and ether soft blocks. Structural changes are induced by chemical degradation from virgin samples through hydrolysis and oxidation. Molar mass measurements show an exclusive chain scission mechanism for all TPEs, regardless of the chemical modification condition. Mechanical behavior was nevertheless obtained from uniaxial tensile testing and fracture testing while considering the essential work of fracture (EWF) concept. During the macromolecular scission process, elongation at break shows a plateau followed by a drop, while stress at break decreases steadily. Once again, the trend is identical for all TPEs in all conditions considered. The βw_p parameter determined using the EWF concept exhibits an interesting sensitivity to scissions (i.e., molar mas decrease). Plotting elongation at break as a function of molar mass reveals a strong correlation between these two parameters. This master curve is particularly remarkable considering the range of TPEs and chemical breakdown pathways considered (hydrolysis and oxidation at several temperatures). Relevant structure–property relationships are proposed, highlighting that molar mass is a predominant parameter for determining the mechanical properties of thermoplastic elastomers.     

Generation and characterization of air micro-bubbles in highly hydrophobic capillaries

The generation of air microbubbles in microfluidic systems or in capillaries could be of great interest for transportation (single cell analysis, organite transportation) or for liquid compartmentation. The physicochemical characterization of air bubbles and a better understanding of the process leading to bubble generation during electrophoresis is also interesting in a theoretical point of view. In this work, the generation of microbubbles on hydrophobic Glaco™ coated capillaries has been studied in water-based electrolyte. Air bubbles were generated at the detection window and the required experimental parameters for microbubbles generation have been identified. Generated bubbles migrated against the electroosmotic flow, as would do strongly negatively charged solutes, under constant electric field. They have been characterized in terms of dimensions, electrophoretic mobility, and apparent charge.     

Synthesis of tetracyclic dioxygenated isoquinolines and their cytotoxic activity

An efficient synthesis of new dioxygenated isoquinolines is reported. The novelty of this approach derives from its use of tricyclic-nitril (3) as a building block in a synthetic sequence of seven steps for the preparation of the tetracyclic isoquinoline (14) and its derivatives. The isoquinoline 16 was 10-fold more active against leukemia L₁₂₁₀ than the corresponding tetrahydroisoquinoline 14.     

A new uranyl niobate sheet in the cesium uranyl niobate Cs9[(UO2)8O4(NbO5)(Nb2O8)2]

A new cesium uranyl niobate, Cs₉[(UO₂)₈O₄(NbO₅)(Nb₂O₈)₂] or Cs₉U₈Nb₅O₄₁ has been synthesized by high-temperature solid-state reaction, using a mixture of U₃O₈, Cs₂CO₃ and Nb₂O₅. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) Å, b=14.933(2) Å, c=20.155(2) Å β=110.59(1)°, P2₁/c space group and Z=4. The crystal structure was refined to agreement factors R₁=0.049 and wR₂=0.089, calculated for 4660 unique observed reflections with I?2σ(I), collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector.In this structure the UO₇ uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb₂O₈ entities and NbO₅ square pyramids, respectively, to form infinite uranyl niobate sheets stacking along the [010] direction. The Nb₂O₈ entities result from two edge-shared NbO₅ square pyramids. The Cs⁺ cations are localized between layers and ensured the cohesion of the structure.The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs⁺ cations to the infinite uranyl niobate layers and by the high density of these cations in the interlayer space without vacant site.Infrared spectroscopy investigated at room temperature in the frequency range 400-4000 cm⁻¹, showed some characteristic bands of uranyl ion and niobium polyhedra.     

Chemiluminescent probe for the in vitro detection of protease activity

A strategy involving the use of a self-immolative linker has been investigated for the chemiluminescent sensing of proteases. The reactive linker enabled the release of a 1,2-dioxetane light precursor. As a proof of principle, caspase-3, a key peptidase involved in apoptosis has been targeted. An in vitro assay has been carried out and proved the decomposition of the linker and the selectivity for caspase-3.     

Use of 1,10-phenanthroline in diiron dithiolate derivatives related to the [Fe-Fe] hydrogenase active site

Treatment of [Fe(2)(micro-pdt)(CO)(6)] (pdt = S(CH(2))(3)S) with 1,10-phenanthroline (phen) in refluxing toluene affords the asymmetric complex [Fe(2)(micro-pdt)(CO)(4)(phen)] (1); the protonation of with HBF(4).OEt(2) in CD(2)Cl(2) at 203 K has been monitored by (1)H NMR.     

The \gamma \gamma \to \gamma Z process at high energies and the search for virtual SUSY effects

We study the helicity amplitudes and the observables of the process at high energy. As in the case of the process studied before, the relevant diagrams in the standard model (SM) involve W, charged-quark, and lepton loops, while in SUSY we also have contributions from charginos and charged-sfermion or Higgs-loop diagrams. Above 250 GeV, the dominant SM amplitudes are themselves dominated by the W loop, and as for , they are helicity conserving and almost purely imaginary. We discuss the complementary information provided by for the identification of possible nonstandard effects. This process, together with , should provide very useful information on the nature of possible new physics particles, above the threshold of their direct production. Received: 26 April 1999 / Published online: 8 September 1999