Vandermonde sets and super-Vandermonde sets

Given a set TGF(q), |T|=t, w_T is defined as the smallest positive integer k for which ∑_yTy^k≠0. It can be shown that w_Tt always and w_Tt−1 if the characteristic p divides t. T is called a Vandermonde set if w_Tt−1 and a super-Vandermonde set if w_T=t. This (extremal) algebraic property is interesting for its own right, but the original motivation comes from finite geometries. In this paper we classify small and large super-Vandermonde sets.     

Thermal behaviour and electrochemical properties of bis(trifluoromethanesulfonyl)amide and dodecatungstosilicate viologen dimers

We report the synthesis and characterization of dimeric viologen salts (1',1'-(alkane-1,n-diyl)bis(1-ethyl-4,4'-bipyridinium) with n = 4-10) with bis(trifluoromethanesulfonyl)amide (bistriflimide, Tf(2)N(-)) as a counteranion. For n = 4, 5 and 6, and for the nonylviologen cation (1,1'-dinonyl-4,4'-bipyridinium) we also prepared salts with the totally inorganic dodecatungstosilicate anion, SiW(12)O(40)(4-), featuring a poly-charged surface and nanosized dimensions. The materials have been characterized by means of calorimetric techniques, X-ray diffraction and solid state NMR and a comparison is made with analogous monomeric viologen salts exhibiting smectic mesophases. A strong odd-even effect is observed in the melting points and in the thermal behaviour of the bistriflimide dimeric systems, similar to what was reported for dipolar calamitic liquid crystal dimers, although the studied viologen dimers are not mesomorphic. By increasing the size of the counteranion we have observed a destabilization of the crystal phases and of the mesophases in favour of a glassy amorphous state. Implications on the design of novel ionic liquid crystals are discussed. The electrochemical behaviour in solution has been investigated by cyclic voltammetry measurements: interestingly, the odd-even effect is clearly visible also in the redox potentials. The spin-pairing of the viologen radical cations formed at each end of the dimer is responsible for the observed redox trend. Insights on the structure of the spin-paired dimer have been obtained by DFT calculations.     

A flow injection analyser conductometric coupled system for the field analysis of free dissolved CO<Subscript>2</Subscript> and total dissolved inorganic carbon in natural waters

A flow injection analyser coupled with a gas diffusion membrane and a conductometric microdetector was adapted for the field analysis of natural concentrations of free dissolved CO₂ and dissolved inorganic carbon in natural waters and used in a number of field campaigns for marine water monitoring. The dissolved gaseous CO₂ presents naturally, or that generated by acidification of the sample, is separated by diffusion using a hydrophobic semipermeable gas porous membrane, and the permeating gas is incorporated into a stream of deionised water and measured by means of an electrical conductometric microdetector. In order to make the system suitable and easy to use for in-field measurements aboard oceanographic ships, the single components of the analyser were compacted into a robust and easy to use system. The calibration of the system is carried out by using standard solutions of potassium bicarbonate at two concentration ranges. Calibration and sample measurements are carried out inside a temperature-constant chamber at 25 °C and in an inert atmosphere (N₂). The detection and quantification limits of the method, evaluated as 3 and 10 times the standard deviation of a series of measurements of the matrix solution were 2.9 and 9.6 μmol/kg of CO₂, respectively. Data quality for dissolved inorganic carbon was checked with replicate measurements of a certified reference material (A. Dickson, Scripps Institution of Oceanography, University of California, San Diego), both accuracy and repeatability were −3.3% and 10%, respectively. Optimization, performance qualification of the system and its application in various natural water samples are reported and discussed. In the future, the calibration step will be operated automatically in order to improve the analytical performance and the applicability will be increased in the course of experimental surveys carried out both in marine and freshwater ecosystems. Considering the present stage of development of the method, it can only be applied for studying of the carbon cycle in oxic environments.     

Detection of DNA hybridization on chemically modified graphene platforms

The increasing demand for simple, low-cost, rapid, sensitive and label-free methods for the detection of DNA sequences and the presence of single nucleotide polymorphisms (SNPs) has become an important issue in biomedical research. In this work, we studied the performances of several chemically modified graphene nanomaterials as sensing platforms by using the electrochemical impedance spectroscopy technique for the detection. We employed a hairpin DNA as a highly selective probe for the detection of SNP correlated to Alzheimer's disease. We believe that our findings may present a foundation for further research and development in graphene-based impedimetric biosensing.     

A 2DE approach for high-throughput antigen separation applicable to mAb production

A constantly increasing number of mABs are required for the validation of a large proportion of proteomic and protein-protein interaction data. The development of new robotic platforms has greatly enhanced the throughput of monoclonal antibody production; however, the availability of highly purified proteins to use as antigens currently represents the major bottleneck of the process. In this article, we describe a new 2DE approach to purify hundreds of proteins from cellular extracts in a very cost-effective and time-efficient way. The accuracy of the new purification method is shown to be comparable to high-resolution analytical 2DE. The effectiveness and the throughput of the method to purify proteins suitable for the development of mAbs are then assessed. Using this methodology, we were able to separate 447 proteins starting from 50 mg of proteins extracted from HT29 cells. Fractions containing more than 30 μg of protein constantly induced immunization in mice. Using a high-throughput process for monoclonal antibody production, we obtained an average of 3.5 mAbs for each protein. According to pilot experiments, we can predict that starting from an unfractionated cellular extract it is possible to obtain approximately 200 proteins usable for monoclonal antibody development. Our results indicate that the number of antigens available for monoclonal antibody production can be further increased by running parallel separations. The proposed methodology will then facilitate the high-throughput monoclonal antibody process providing a vast array of high quality antigens at very low cost.     

Solvent-free, heterogeneous photooxygenation of hydrocarbons by hyflon membranes embedding a fluorous-tagged decatungstate

Hybrid fluoropolymeric membranes with 25% loading of the fluorous-tagged (RfN)4W10O32 effect the solvent-free photooxygenation of benzylic C-H bonds with up to 6100 TONs in 4 hours.     

Proton transfer in imidazole-based molecular crystals

Heterocycles' aggregates show rather good proton conductivity. In particular, condensed structures formed by imidazole rings that are held together by polymeric chains have attracted some interest as possible candidate materials for fuel cell membranes. However, the details of the proton diffusion process could not be resolved by means of experimental measurements because of the fast rearrangement of the structure after each proton exchange. In this work, we report in detail the results of ab initio molecular dynamics calculations, which were briefly presented in a previous Letter [M. Iannuzzi and M. Parrinello, Phys. Rev. Lett. 93, 025901 (2004)]. The conformational changes associated with the diffusion of protons in model crystalline structures containing chains of imidazole rings are described in the framework of an atomistic approach. In particular, the bonding pattern characterizing the structure of imidazole-2-ethylene-oxide doped by an excess proton is also studied through the calculation of the 1H NMR chemical shifts. The unresolved resonances appearing in the experimental spectra could be associated with specific structural features, in connection with the fluctuating hydrogen bonding. The analysis of the distortions that induce or are induced by the mobility of the protons offers some new hints for the engineering of new proton conducting materials.     

Electrochemical behavior of 5-type phosphodiesterase inhibitory drugs in solid state by voltammetry of immobilized microparticles

Journal of Solid State Electrochemistry - Evaluation of electrochemical behavior of 5-type phosphodiesterase inhibitory drugs is of major concern since they have been added illegally as adulterants...