Incorporation of chemical functionalities in the framework of mesoporous silica

Mesoporous silica, which shows well-defined pore systems, tunable pore diameters (2-30 nm), narrow pore size distributions and high surface areas (>600 m(2) g(-1)), is frequently modified using different methodologies (including in situ and post-synthetic strategies) to introduce various chemical functionalities useful in applications like catalysis, separation, drug delivery, and sensing. This contribution aims to provide a critical overview of the various strategies to incorporate chemical functionalities in mesoporous silica highlighting the advantages of the in situ methods based on the bottom-up construction of mesoporous silica containing various chemical functionalities in its structure.     

Study of the incorporation and release of the non-conventional half-sandwich ruthenium(II) metallodrug RAPTA-C on a robust MOF

The highly porous and robust [Ni(8)(OH)(4)(OH(2))(2)(4,4'-(buta-1,3-diyne-1,4-diyl)bispyrazolato)(6)](n) MOF can be used as a proof of concept for the incorporation and release of the non-conventional [Ru(p-cymene)Cl(2)(pta)] RAPTA-C metallodrug.     

Capture of nerve agents and mustard gas analogues by hydrophobic robust MOF-5 type metal-organic frameworks

In this communication, a series of observations and data analyses coherently confirms the suitability of the novel metal-organic framework (MOF) [Zn(4)(μ(4)-O)(μ(4)-4-carboxy-3,5-dimethyl-4-carboxy-pyrazolato)(3)] (1) in the capture of harmful volatile organic compounds (VOCs). It is worthy of attention that 1, whose crystal structure resembles that of MOF-5, exhibits remarkable thermal, mechanical, and chemical stability, as required if practical applications are sought. In addition, it selectively captures harmful VOCs (including models of Sarin and mustard gas, which are chemical warfare agents), even in competition with ambient moisture (i.e., under conditions mimicking operative ones). The results can be rationalized on the basis of Henry constant and adsorption heat values for the different essayed adsorbates as well as H(2)O/VOC partition coefficients as obtained from variable-temperature reverse gas chromatography experiments. To further strengthen the importance of 1, its performance in the capture of harmful VOCs has been compared with those of well-known materials, namely, a MOF with coordinatively unsaturated metal sites, [Cu(3)(btc)(2)] and the molecular sieve active carbon Carboxen. The results of this comparison show that coordinatively unsaturated metal sites (preferential guest-binding sites) are ineffective for the capture of VOCs in the presence of ambient moisture. Consequently, we propose that the driving force of the VOC-MOF recognition process is mainly dictated by pore size and surface hydrophobicity.     

Influence of the chemical structure of water-soluble cryptophanes on their overall chiroptical and binding properties

The synthesis and the chiroptical properties of the two enantiomers of the hexacarboxylic acid cryptophane-A derivative, 1, are described in this article. The chiroptical and binding properties of 1 toward achiral and chiral guests have been investigated in water under basic conditions by polarimetry, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and (1)H NMR spectroscopy. These experiments reveal that the (1)H NMR spectra of 1 are very sensitive to the nature of the guest trapped in its cavity whereas ECD and VCD spectra remain unchanged. We also show that the two enantiomers of 1 are able to distinguish between the two enantiomers of a series of small chiral epoxides. The enantiodiscrimination increases with the size of the chiral guest whereas the corresponding binding constants decrease. In contrast to what was observed for other water-soluble cryptophanes, the molecular recognition process is found independent of the nature of the counterions surrounding host 1, shedding light on the importance of the chemical structure of cryptophanes on their binding and chiroptical properties.     

On Decay Properties of Solutions of the k-Generalized KdV Equation

We prove special decay properties of solutions to the initial value problem associated to the k-generalized Korteweg-de Vries equation. These are related with persistence properties of the solution flow in weighted Sobolev spaces and with sharp unique continuation properties of solutions to this equation. As an application of our method we also obtain results concerning the decay behavior of perturbations of the traveling wave solutions as well as results for solutions corresponding to special data.     

Combining linear programming and automated planning to solve intermodal transportation problems

When dealing with transportation problems Operational Research (OR), and related areas as Artificial Intelligence (AI), have focused mostly on uni-modal transport problems. Due to the current existence of bigger international logistics companies, transportation problems are becoming increasingly more complex. One of the complexities arises from the use of intermodal transportation. Intermodal transportation reflects the combination of at least two modes of transport in a single transport chain, without a change of container for the goods. In this paper, a new hybrid approach is described which addresses complex intermodal transport problems. It combines OR techniques with AI search methods in order to obtain good quality solutions, by exploiting the benefits of both kinds of techniques. The solution has been applied to a real world problem from one of the largest spanish companies using intermodal transportation, Acciona Transmediterránea Cargo.     

Two-dimensional atom-phonon coupling model for spin conversion: role of metastable states

Spin conversion, (SC), compounds are composed of molecules organized around a transition metal ion. The ion spin value is smaller for the ion fundamental level than for its first excited one. So, increasing the temperature changes the spin mean value. This spin conversion can be continuous or can display a first order phase transition called spin transition. The atom phonon coupling model, introduced recently, allows to describe at least qualitatively different experimental results. Up to now, this model has been applied on a linear chain of atoms. In this paper we apply it on a square lattice. We study the thermal variations of different thermodynamic parameters and the metastable states which are present around the transition. In this study, it is expected that the critical point of some (SC) compounds can be reached by applying on them a small hydrostatic pressure; it is also expected that ultrasound pulses can induce, at a very low temperature, a conversion between the stable low spin state and the metastable high spin state and it is also predicted that the crystal sound velocity can display a discontinuity at the first order phase transition.     

Design parameters for continuously variable power-split transmissions using planetaries with 3 active shafts

Since 1996, when the first agricultural tractor with CVT transmission was shown, the presence of this type of transmissions has been increasing. All companies offer them in their products range. Nevertheless, there is little technical documentation that explains the basics of its operation. This report shows all types of CVT transmissions: non-power-split type and power-split ones, as well as the three types used in agricultural tractors, hydro-mechanical power-split transmissions (3 active shafts, input coupled planetary; 3 active shafts, output coupled planetary and 4 active shafts). The report also describes the design parameters of a type of CVT transmission, which use a power-split system with 3 active shafts as well as the fundamental relations among them.     

Two-step spin conversion and other effects in the atom-phonon coupling model

We study an atom-phonon coupling model introduced recently for spin-conversion phenomenon. The originality of this model, performed on a linear chain of atoms, is that the elastic force constant values of the spring linking two atoms depends on their electronic states. This leads to introduce naturally in the chain long- and short-range interactions, which appear respectively like a Zeeman and an exchange interactions. The exchange-like interaction can be ferro-, antiferro- or equal to zero. The effects of long-range interactions have already been studied. Here we study those of the short-range interaction. Some parts of the chain phase diagram are analysed and the main features of the experimental behaviours of spin conversion compounds are qualitatively reproduced.Received: 2 February 2004, Published online: 29 June 2004PACS: 63.20.Kr Phonon-electron and phonon-phonon interactions - 63.50. + x Vibrational states in disordered systems - 64.60.-i General studies of phase transitions     

A Palette of Fluorescent Thiophene‐Based Ligands for the Identification of Protein Aggregates

By replacing the central thiophene unit of an anionic pentameric oligothiophene with other heterocyclic moities, a palette of pentameric thiophene‐based ligands with distinct fluorescent properties were synthesized. All ligands displayed superior selectivity towards recombinant amyloid fibrils as well as disease‐associated protein aggregates in tissue sections.