Synthesis of a Key Intermediate for the Synthesis of Pyranocoumarins. Contrasting Reactivity in the 1,2-and 1,4-Reduction of an Unsaturated Carbonyl System

[2,2-dimethyl-4-(t-butyldimethylsiloxy)-3,4-dihydro-2H-pyran-6-yl] methanal (1) was synthesized from commercially available butopyronoxyl (2). The selectivity of reducing agents such as DIBAL-H and LiAlH₄ towards butopyronoxyl was studied. Solvent effects were found to influence 1,2 versus 1,4 reduction.     

Localization Results for the Meyer-König and Zeller Max-Product Operator

In this article, we investigate the local approximation and shape preserving properties in subintervals for the Meyer-König and Zeller max-product operators. The results obtained put in evidence that in the class of strictly positive continuous functions, the local properties of the nonlinear Meyer-König and Zeller max-product operators are much stronger and more general than those in the case of their linear counterparts.     

Silica matrices for embedding of magnetic nanoparticles

This paper presents a study regarding the formation of hybrid gels starting from tetraethyl orthosilicate (TEOS), polyvinyl alcohol (PVA) and 1,3-propanediol (PD) and their thermal evolution to mesoporous silica matrices. The possibility of obtaining homogenously dispersed cobalt ferrite inside the silica matrix starting from (TEOS–PVA–PD–Metal Nitrates) gels was also studied. The formation of the hybrid gels TEOS/PVA/PD with different compositions was studied by FT-IR spectrometry and thermal analysis, in order to evidence the interaction between the diol with the organic and the inorganic polymers. Both thermal analysis and FT-IR spectrometry have evidenced the formation of physical and chemical interaction between polyols and the siloxane network. Elemental mapping performed by SEM-EDX technique evidenced the formation of homogenous hybrids both in the presence of the absence of 1,3-propanediol. SEM images of the powders obtained by annealing the hybrid xerogels at 600 °C have evidenced the formation of mesoporous silica. By thermal treatment of the (TEOS–PVA–PD–Metal Nitrates) gels, 30%CoFe₂O₄/70%SiO₂ (mass percent) nanocomposites uniformly dispersed in silica matrix with characteristic magnetic properties, have been successfully synthesized.     

Determination of Xenoestrogenic Compounds Using a Nanostructured Biosensing Device

A ternary composite material based on Prussian blue, single‐walled carbon nanotubes and 1‐butyl‐3‐methylimidazolium hexafluorophosphate was prepared and tested for electrochemical detection of H₂O₂. The sensor allows amperometric detection of H₂O₂ at ?0.05 V, with a sensitivity of 137 mA M^?1?cm^?2. The nanocomposite provides a favorable microenvironment for immobilization of horseradish peroxidase (HRP). Determination of xenoestrogenic compounds was performed by enzymatic oxidation at the surface of modified screen printed biosensor in the presence of H₂O₂. The developed electrochemical biosensors exhibited high sensitivity, low detection limits, good operational and storage stability, for detection of 4‐t‐butylphenol, 4‐t‐octylphenol, 4‐n‐nonylphenol and 4‐n‐nonylphenol ethoxylate.     

Synergistic effect of mediator–carbon nanotube composites for dehydrogenases and peroxidases based biosensors

Very sensitive, low cost and reliable NADH and H₂O₂ sensors were realised and used for development of enzyme based biosensors. The active surface of the electrodes was modified with a nanocomposite obtained by modification of SWNT with a proper mediator: Meldola Blue (for NADH) and Prussian Blue (for H₂O₂). Low applied potential of − 50 mV vs. Ag/AgCl reference electrode proved the synergistic effect of nanocomposite materials towards NADH and H₂O₂ detection. Biosensors for malic acid and alkylphenols have been developed, using mediator-functionalised-SWNT-based electrodes and two different classes of enzymes: NAD⁺-dependent dehydrogenases and peroxidases. Immobilization of the enzymes was realised using a series of different procedures — adsorption, Nafion membrane, sol–gel and glutaraldehyde, in order to find the best configuration for a good operational stability. A higher sensitivity comparing with other reported biosensors of about 12.41 mA/M·cm² was obtained for l-malic acid biosensor with enzyme immobilised in Nafion membrane. Phenol, 4-t-octylphenol and 4-n-nonylphenol were used as standard compounds for HRP based biosensor. Fast biosensor response and comparable detection limit with HPLC methods were achieved.     

Strategies for the Synthesis of Functional Naphthalene Diimides

Naphthalene diimides, which have for a long time been in the shadow of their higher homologues the perylene diimides, currently belong to the most investigated classes of organic compounds. This is primarily due to the initial synthetic studies on core functionalization that were carried out at the beginning of the last decade, which facilitated diverse structural modifications of the naphthalene scaffold. Compounds with greatly modified optical and electronic properties that can be easily and effectively modulated by appropriate functionalization were made accessible through relatively little synthetic effort. This resulted in diverse interesting applications. The electron‐deficient character of these compounds makes them highly valuable, particularly in the field of organic electronics as air‐stable n‐type semiconductors, while absorption bands over the whole visible spectral range through the introduction of core substituents enabled interesting photosystems and photovoltaic applications. This Review provides an overview on different approaches towards core functionalization as well as on synthetic strategies for the core expansion of naphthalene diimides that have been developed mainly in the last five years.     

Feyel's Techniques on the Supermedian Functionals and Strongly Supermedian Functions

We study the strongly supermedian functions and the supermedian functionals associated with a submarkovian resolvent on a Lusin space. We extend results of D. Feyel and J. F. Mertens to a general right process. The existence of a positive potential replaces the usual hypothesis that the process possesses left limits in the space.     

Iodidomesityltellurium(II) iodidotrimesitylditellurium(II)(Te—Te)

In the title compound, C₉H₁₁ITe·C₂₇H₃₃ITe₂ or (Mes)TeI·(Mes₂Te)TeI(Mes) (Mes is mesityl or 2,4,6‐trimethylphenyl), a strong Te...I interaction of 3.3157 (9) Å links the Te atom of an iodidomesityltellurium(II) moiety, (Mes)TeI, and an I atom of the iodidotrimesitylditellurium(II) unit, (Mes₂Te)TeI(Mes). Further weak Te...I contacts of 4.0818 (9) Å give rise to one‐dimensional chains along the b axis in the crystal structure. An intramolecular C—H...π(arene) interaction is present in the (TeMes₂)TeI(Mes) moiety, with a C...Cg distance of 3.497 (9) Å and a C—H...Cg angle of 142° (where Cg is the centroid of a mesityl ring of the Mes₂Te moiety).     

Some aspects concerning the design of an immunomagnetic separation process

We used a stochastic model and have performed a series of numerical simulations to optimise the step of microorganisms collection on magnetic carrier particles. We obtained that the time of capture depends on concentration of carrier particles in suspension, their size, the volume fraction of magnetite in the composite material, the applied magnetic field intensity and its gradient, the size and density of micro-organisms to be collected and the density and viscosity of the liquid in which the particles are suspended.     

Sub-Markovian resolvents under weak duality hypothesis

 We study the weak duality between two sub-Markovian resolvents of kernels on a Lusin topological space with respect to a given measure m. Our frame covers the probabilistic context of two Borel Markov processes in weak duality. The main results are related to: the coincidence of the m-semipolar and m-cosemipolar sets, the Revuz correspondence between the measures charging no cofinely open m-polar set and the potential kernels associated with the homogeneous random measures of the process, the equivalence between smoothness and cosmoothness (a smooth measure is the Revuz measure of a continuous additive functional). We extend and improve results of R.M. Blumenthal-R.K. Getoor, J. Azéma, D. Revuz, J.B. Walsh, R.K. Getoor-M.J. Sharpe. Received: 24 July 2001 / Revised version: 29 December 2002 / Published online: 12 May 2003 Supported by the CNCSIS grant no. 33518/2002 (code 431), the CERES program of the Romanian Ministry of Ed. and Research, contract no. 152/2001 and the EURROMMAT program ICA1-CT-2000-70022 of the European Commission. Mathematics Subject Classification (2000): 60J40, 60J45, 60J55, 60J35, 31C15, 31C25, 31D05