Characterization of dendrimer properties by capillary electrophoresis and their use as pseudostationary phases

The general properties of dendrimers and in particular their electrolytic characteristics that are relevant in electrokinetic separations, are described. In order to confirm theoretical considerations on commercial dendrimer charge and hydrodynamic radius, several capillary zone electrophoresis (CZE) experiments were performed. Electrophoretic mobilities measured at different pH values indicated a sensible increase of dendrimer hydrodynamic radius at pH values lower than 2.5. This was probably due to the Coulombic repulsion of charged amine groups of the inner dendrimer shells. The principal reasons that should address the use of dendrimers as pseudostationary phases in micellar electrokinetic chromatography (MEKC) are discussed. Moreover, a survey of different separations performed utilizing dendrimers in MEKC as well as of several future plausible uses of various classes of dendrimers is presented.     

Improved rapid assay of plasma uric acid by short-end injection capillary zone electrophoresis

A rapid and simple short-end injection capillary zone electrophoresis method was developed for the quantification of plasma uric acid. The separation was performed in an uncoated fused-silica capillary (50 μm ID, 60 cm total length, 10.2 cm effective length) by using as a background electrolyte a 75 mmol/L glycylglycine solution titrated with NaOH 5 mol/L to pH 9.0, a voltage of 28 kV, a cartridge temperature of 15 °C, and direct UV detection at 292 nm. Under optimized conditions, uric acid was determinate in little more than 1 min (1.076 minutes). In order to verify the accuracy of the analysis, urate levels were measured in 543 apparently healthy volunteers by the new assay and our previous method, and the obtained data were compared by Passing–Bablock regression, Bland–Altman test, and a new regression-based approach, which showed a good agreement between two methods.     

Surface-activated chemical ionization ion trap mass spectrometry for the analysis of cocaine and benzoylecgonine in hair after extraction and sample dilution

Surface-activated chemical ionization (SACI) was employed for the analysis of cocaine and its metabolite, benzoylecgonine, extracted from hair. Following decontamination and acid hydrolysis procedures on the hair sample, the sample solution was diluted (1:10) and directly analyzed by liquid chromatography/surface-activated chemical ionization multiple collisional stage single reaction monitoring mass spectrometry (LC/SACI-MS(3)-SRM) without solid-phase extraction (SPE) pre-purification and concentration procedures. To increase the selectivity of the method, MS(3) was chosen instead of the less selective MS/MS. This data was compared with that achieved using gas chromatography/mass spectrometry (GC/MS), the reference method used by the Italian Government Institute of Health protocol. The limits of detection (LODs) were 0.003 ng/(mg hair) for cocaine and 0.02 ng/(mg hair) for benzoylecgonine and the limits of quantitation (LOQs) were 0.01 ng/(mg hair) for cocaine and 0.04 ng/(mg hair) for benzoylecgonine. The squared correlation coefficient (R(2)) of the calibration curve was 0.9887-0.9980 for cocaine and 0.9987-0.9997 for benzoylecgonine. The percent accuracy error was 2-5% for both cocaine and benzoylecgonine using the LC/SACI-MS(3)-SRM approach, whereas it was higher for benzoylecgonine (20-25%) using the LC/SACI-MS/MS-SRM approach compared with the GC/MS data due to hair matrix contamination. In both cases, high precision was achieved (1-3% precision error), which confirmed the stability of the developed methods.     

Multi-phase epidemic model by a Markov chain

In this paper we propose a continuous-time Markov chain to describe the spread of an infective and non-mortal disease into a community numerically limited and subjected to an external infection. We make a numerical simulation that shows tendencies for recurring epidemic outbreaks and for fade-out or extinction of the infection.     

Enzyme-mediated synthesis of EEHP and EMHP,useful pharmaceutical intermediates of PPAR agonists

A new scaleable synthetic route to the title compounds has been developed. The reaction pathway is based on the α-chymotrypsin-catalysed hydrolysis of the racemic ethyl 2-ethoxy-3-(p-methoxyphenyl)propanoate or of the racemic ethyl 2-methoxy-3-(p-methoxyphenyl)propanoate to give the corresponding resolved (S)-esters with excellent ee. The acids were easily separated from the (S)-esters by a simple acid–base work-up. The overall yields of 1 and 2 were 16% and 17%, respectively.     

Global existence of strong solutions to the one-dimensional full model for phase transitions in thermoviscoelastic materials

This paper is devoted to the analysis of a one-dimensional model for phase transition phenomena in thermoviscoelastic materials. The corresponding parabolic-hyperbolic PDE system features a strongly nonlinear internal energy balance equation, governing the evolution of the absolute temperature ϑ, an evolution equation for the phase change parameter χ, including constraints on the phase variable, and a hyperbolic stress-strain relation for the displacement variable u. The main novelty of the model is that the equations for χ and u are coupled in such a way as to take into account the fact that the properties of the viscous and of the elastic parts influence the phase transition phenomenon in different ways. However, this brings about an elliptic degeneracy in the equation for u which needs to be carefully handled. First, we prove a global well-posedness result for the related initial-boundary value problem. Secondly, we address the long-time behavior of the solutions in a simplified situation. We prove that the ω-limit set of the solution trajectories is nonempty, connected and compact in a suitable topology, and that its elements solve the steady state system associated with the evolution problem. Dedicated to Jürgen Sprekels on the occasion of his 60th birthday     

Bounds in Multistage Linear Stochastic Programming

Multistage stochastic programs, which involve sequences of decisions over time, are usually hard to solve in realistically sized problems. Providing bounds for optimal solution may help in evaluating whether it is worth the additional computations for the stochastic program vs. simplified approaches. In this paper we generalize measures from the two-stage case, based on different levels of available information, to the multistage stochastic programming problems. A set of theorems providing chains of inequalities among the new quantities are proved. Numerical results on a case study related to a simple transportation problem illustrate the described relationships.     

Combining Gene Expression Profiles and Drug Activity Patterns Analysis: A Relational Clustering Approach

The combined analysis of tissue micro array and drug response datasets has the potential of revealing valuable knowledge about various relations among gene expressions and drug activity patterns in tumor cells. However, the amount and the complexity of biological data needs appropriate data mining models in order to extract interesting patterns and useful information. The ultimate goal of this paper is to define a model which, given the gene expression profile related to a specific tumor tissue, could help in selecting a set of most responsive drugs. This is accomplished through an integrated framework based on a constraint-based clustering algorithm, called Relational K-Means, which groups cell lines using drug response information and taking into account cell-to-cell relationships derived from their gene expression profiles.