Single Drop Dynamics under Shearing Flow in Systems with a Viscoelastic Phase

In this article, we discuss the dynamics of a single drop immersed in an immiscible liquid, under an imposed shear flow. The two situations of a viscoelastic matrix with a Newtonian drop and of a viscoelastic drop in a Newtonian matrix are considered, both systems being characterized by a viscosity ratio equal to one, and by the same elasticity parameter. Experimental data are taken with a rheo-optical computer-assisted shearing device, allowing for drop observation from the vorticity direction of the shear flow. Data favourably compare with predictions of the recently proposed Maffettone-Greco model, where the drop is described as a deforming ellipsoid.     

A Semi Rigid Novel Hydroxamate AMPED-Based Ligand for 89Zr PET Imaging

In this work, we designed, developed, characterized, and investigated a new chelator and its bifunctional derivative for ⁸⁹Zr labeling and PET-imaging. In a preliminary study, we synthesized two hexadentate chelators named AAZTHAS and AAZTHAG, based on the seven-membered heterocycle AMPED (6-amino-6-methylperhydro-1,4-diazepine) with the aim to increase the rigidity of the ⁸⁹Zr complex by using N-methyl-N-(hydroxy)succinamide or N-methyl-N-(hydroxy)glutaramide pendant arms attached to the cyclic structure. N-methylhydroxamate groups are the donor groups chosen to efficiently coordinate ⁸⁹Zr. After in vitro stability tests, we selected the chelator with longer arms, AAZTHAG, as the best complexing agent for ⁸⁹Zr presenting a stability of 86.4 ± 5.5% in human serum (HS) for at least 72 h. Small animal PET/CT static scans acquired at different time points (up to 24 h) and ex vivo organ distribution studies were then carried out in healthy nude mice (n = 3) to investigate the stability and biodistribution in vivo of this new ⁸⁹Zr-based complex. High stability in vivo, with low accumulation of free ⁸⁹Zr in bones and kidneys, was measured. Furthermore, an activated ester functionalized version of AAZTHAG was synthesized to allow the conjugation with biomolecules such as antibodies. The bifunctional chelator was then conjugated to the human anti-HER2 monoclonal antibody Trastuzumab (Tz) as a proof of principle test of conjugation to biologically active molecules. The final ⁸⁹Zr labeled compound was characterized via radio-HPLC and SDS-PAGE followed by autoradiography, and its stability in different solutions was assessed for at least 4 days.     

Synthesis of pyrido[3,2-e]pyrrolo[2,1-c][1,2,4]triazines from pyrido[3,2-e][1,2,4]triazine derivatives

In carrying on our interest in heteropolycyclic structures with biological activities, we projected the preparation of compounds containing the pyrido[3,2-e][1,2,4]triazine or pyrido[2,3-b][1,4]triazepine systems. The established synthetic approach for the preparation of latter system led to the triazine derivatives 5a-f while a new bicyclic triazepine structure 6 is accomplished with difficulty. In expanding the pyridotriazine structure, we obtained derivatives of a new tricyclic structure, 5-substituted-6a-ethyloxycarbonyl-5,6,6a,7-tetrahydropyrido[2,3-e]pyrrolo[2,1-c][1,2,4]triazin-9(8H)-ones 8 in which the triazine ring is fused with a pyrrole nucleus. Compounds 5a-f and 8a,b will be tested as potential CNS depressant, antiinflammatory, analgesic and antibacterial agents.     

Regularity for minimizers of functionals with p – q growth

We prove higher integrability for the gradient of vector-valued minimizers of some integral functionals with p – q growth. Received February 9, 1998     

Acidity of Alginate Aerogels Studied by FTIR Spectroscopy of Probe Molecules

Supercritical drying of alginate gels is an efficient way to prepare aerogels with high surface area (>300 m² · g⁻¹). FTIR spectroscopy allows to monitor the adsorption of NH₃ from the gas phase onto the acid sites of the alginate. Free carboxylic groups are effective Brønsted sites, whereas the divalent cations used in the ionotropic gelation present the properties of Lewis sites. The ratio between Brønsted and Lewis sites provides infomation on the role of pH in alginate gelation and suggests that non-buffered gelation by transition-metal cations is a mixed ionotropic-acid process.     

Multi-instantons, supersymmetry and topological field theories

In this letter we argue that instanton-dominated Green's functions in N=2 Super Yang–Mills theories can be equivalently computed either using the so-called constrained instanton method or making reference to the topological twisted version of the theory. Defining an appropriate BRST operator (as a supersymmetry plus a gauge variation), we also show that the expansion coefficients of the Seiberg–Witten effective action for the low-energy degrees of freedom can be written as integrals of total derivatives over the moduli space of self-dual gauge connections.     

Replica Symmetry Breaking in Short-Range Spin Glasses: Theoretical Foundations and Numerical Evidences

We discuss replica symmetry breaking (RSB) in spin glasses. We update work in this area, from both the analytical and numerical points of view. We give particular attention to the difficulties stressed by Newman and Stein concerning the problem of constructing pure states in spin glass systems. We mainly discuss what happens in finite-dimensional, realistic spin glasses. Together with a detailed review of some of the most important features, facts, data, and phenomena, we present some new theoretical ideas and numerical results. We discuss among others the basic idea of the RSB theory, correlation functions, interfaces, overlaps, pure states, random field, and the dynamical approach. We present new numerical results for the behaviors of coupled replicas and about the numerical verification of sum rules, and we review some of the available numerical results that we consider of larger importance (for example, the determination of the phase transition point, the correlation functions, the window overlaps, and the dynamical behavior of the system).     

Hydrogenation of Quinoline by Rhodium Catalysts Modified with the Tripodal Polyphosphine Ligand MeC(CH2PPh2)3

As part of our modelling studies of the hydrodenitrogenation of N‐heterocycles contained in raw oil materials, we investigated the selective hydrogenation of quinoline to 1,2,3,4‐tetrahydroquinoline by rhodium catalysts modified with the tripodal polyphosphane ligand MeC(CH₂PPh₂)₃. Experiments in standard autoclaves and in high‐pressure sapphire NMR tubes, kinetic and isotope labelling studies, and independent reactions with isolated compounds have contributed to the elucidation of the catalytic mechanism as well as identification of the electronic requisites of the metal catalyst for selective and efficient hydrogenation.     

Configuration,Conformation, and Reactivity of Highly Functionalized Eunicellane Diterpenes Isolated from the Gorgonians Eunicella cavolinii and Eunicella singularis from Marseille

Eunicellane diterpenes with a C(7)=C(16) (Δ^7,16; see 17 – 19 ), (Z)‐C(7)=C(8) ((7Z)Δ^7,8; see 20 – 23 ), and (Z)‐C(6)=C(7) ((6Z)Δ^6,7; see 10 ) bond, an uncommon feature in the case of extensive functionalization at the cyclohexane ring and the latter exhibiting uncommon configurations, were isolated from the gorgonian Eunicella cavolinii from Marseille (Figs. 5 and 2). The gorgonian Eunicella singularis (=Eunicella stricta) from the same area gave (7Z)Δ^7,8, Δ^7,16, and (6E)Δ^6,7 analogs 24 , 25 , and 13 , respectively (Fig. 5 and Scheme). The (6E)Δ^6,7 moiety of 13 – characterized by a slow 180° conformational flipping (Fig. 3) that results in broadening of NMR signals – makes the macrocycle highly strained. This may explain the spontaneous conversion of 13 to the 6‐methoxy‐7‐hydroxy derivative 14 in the presence of MeOH at −20° in the dark (Scheme). The isomeric, deacylated analogue 10 showed only little broadening of NMR signals and proved stable, in accordance with the less strained nature of this compound (Fig. 4).