A new method for strategic decision-making in higher education

Central European Journal of Operations Research - Using the appropriate methodology for strategic decision-making in higher education is crucial to make effective decisions. In this paper, the...     

Analysis and numerical simulation of magnetic forces between rigid polygonal bodies. Part II: Numerical simulation

The analysis of magnetoelastic phenomena is a field of active research. Formulae for the magnetic force in macroscopic systems have been under discussion for some time. In Popović et al. (Continum. Mech. Thermodyn. 2007), we rigorously justify several of the available formulae in the context of rigid bodies in two and three space dimensions. In the present, second part of our study, we investigate these formulae in a series of numerical experiments in which the magnetic force is computed in dependence on the geometries of the bodies as well as on the distance between them. In case the two bodies are in contact, i.e., in the limit as their distance tends to zero, we focus especially on a formula obtained in a discrete-to-continuum approximation. The aim of our study is to help clarify the question which force formula is the correct one in the sense that it describes nature most accurately and to suggest adequate real-life experiments for a comparison with the provided numerical data.      

Rigorous Asymptotic Expansions for Critical Wave Speeds in a Family of Scalar Reaction-Diffusion Equations

We investigate traveling wave solutions in a family of reaction-diffusion equations which includes the Fisher–Kolmogorov–Petrowskii–Piscounov (FKPP) equation with quadratic nonlinearity and a bistable equation with degenerate cubic nonlinearity. It is known that, for each equation in this family, there is a critical wave speed which separates waves of exponential decay from those of algebraic decay at one of the end states. We derive rigorous asymptotic expansions for these critical speeds by perturbing off the classical FKPP and bistable cases. Our approach uses geometric singular perturbation theory and the blow-up technique, as well as a variant of the Melnikov method, and confirms the results previously obtained through asymptotic analysis in [J.H. Merkin and D.J. Needham, (1993). J. Appl. Math. Phys. (ZAMP) A, vol. 44, No. 4, 707–721] and [T.P. Witelski, K. Ono, and T.J. Kaper, (2001). Appl. Math. Lett., vol. 14, No. 1, 65–73].     

Cluster‐based molecular docking study for in silico identification of novel 6‐fluoroquinolones as potential inhibitors against Mycobacterium tuberculosis

A classical protein sequence alignment and homology modeling strategy were used for building three Mycobacterium tuberculosis‐DNA gyrase protein models using the available topoII‐DNA‐6FQ crystal structure complexes originating from different organisms. The recently determined M. tuberculosis‐DNA gyrase apoprotein structures and topoII‐DNA‐6FQ complexes were used for defining the 6‐fluoroquinolones (6‐FQs) binding pockets. The quality of the generated models was initially validated by docking of the cocrystallized ligands into their binding site, and subsequently by quantitative evaluation of their discriminatory performances (identification of active/inactive 6‐FQs) for a set of 145 6‐FQs with known biological activity values. The M. tuberculosis‐DNA gyrase model with the highest estimated discriminatory power was selected and used afterwards in an additional molecular docking experiment on a mixed combinatorial set of 427 drug‐like 6‐FQ analogs for which the biological activity values were predicted using a prebuilt counter‐propagation artificial neural network model. A novel three‐level Boolean‐based [T/F (true/false)] clustering algorithm was used to assess the generated binding poses: Level 1 (geometry properties assessment), Level 2 (score‐based clustering and selection of the (T)‐signed highly scored Level 1 poses), and Level 3 (activity‐based clustering and selection of the most “active” (T)‐signed Level 2 hits). The frequency analysis of occurrence of the fragments attached at R₁ and R₇ position of the (T)‐signed 6‐FQs selected in Level 3 revealed several novel attractive fragments and confirmed some previous findings. We believe that this methodology could be successfully used in establishing novel possible structure‐activity relationship recommendations in the 6‐FQs optimization, which could be of great importance in the current antimycobacterial hit‐to‐lead processes. © 2012 Wiley Periodicals, Inc.     

Zaleplon co-ground complexes with natural and polymeric β-cyclodextrin

In this study, we compared the suitability of parent β-cyclodextrin (βCD) and its water soluble polymeric derivative (PβCD) as co-grinding additives aimed to enhance the solubility of zaleplon (ZAL), a hypnotic drug. Equimolar drug/carrier mixtures were co-ground in a high-energy micromill over different time intervals. Data obtained by differential scanning calorimetry, X-ray powder diffractometry and scanning electron microscopy showed a higher affinity of ZAL for the solid state interaction with PβCD, resulting in powders with lower relative drug crystallinity (RDC) compared to that obtained with natural βCD (RDC = 51.10 and 12.5 % for complexes with βCD and PβCD co-grounded for 90 min, respectively). On the other hand, grinding the drug alone did not result in a significant reduction of the drug crystallinity (RDC = 99.87 % for the sample ground for 90 min). Although ¹H-NMR spectroscopy confirmed that both co-ground products were readily converted into inclusion complexes upon dissolution in water, they presented different dissolution properties. The dissolution velocity of co-ground complex with PβCD was 25 % faster compared to that prepared with the parent βCD and almost double compared to that of the drug alone, irrespective of the pH value of the dissolution media. This clearly demonstrated the suitability of co-ground ZAL/PβCD complex in the development of an immediate release oral formulation of ZAL.     

A primitive model for hexamethylpararosaniline (crystal violet) monomolecular adlayer: a Monte Carlo simulation study

The NVT Monte Carlo simulation results are reported for a model of two-dimensional (2D) chemically associating fluid with six attractive sites per monomer disc. Three of these sites are of the type α and the other three of the type β. The sites α and β are fixed inside a hard core, they follow each other anticlockwise, with a `valence' angle of 60°. It is assumed that only α+β site–site association of two different discs occurs. Complex formation, dependent on the density and association energy, is much more sophisticated, in comparison to previously studied models of dimerizing and polymerizing discs. An analysis of complexes in terms of the fractions of singly, doubly,…, hexa-bonded particles is performed, and the dimensions and distributions of complexes are studied. We obtained the pair distribution functions of particles and structure factor in the fluid layer. The model was inspired by experiments on visualization of organic monolayers in the framework of scanning tunneling microscopy (STM). Currently it yields a preliminary insight into the molecular organization of crystal violet molecules on the iodine covered (111) single-crystal surface plane observed experimentally. Extensions of the model and methodology are discussed.     

Novel 2,4-methanoadamantane-benzazepine by domino photochemistry of N-(1-adamantyl)phthalimide

The photochemical reaction of N-(1-adamantyl)phthalimide (1) gives cleanly one product, the novel hexacyclic benzazepine derivative of 2,4-methanoadamantane 2. Its structure was characterized by spectroscopic methods and X-ray analysis and represent the first example of the 2-azahexacyclo[8.7.1.1 (1,4).0 (4,9).0 (11,16).0 (12,18)]nonadeca-4,6,8-triene skeleton. The product is formed by a domino process of two consecutive excited-state intramolecular gamma-hydrogen-transfer reactions. Base hydrolysis of the benzazepine 2 gives in high yield the keto derivative of the 1,2-substituted adamantane epsilon-amino acid 3.     

Adamantane-retropeptides, new building blocks for molecular channels

Novel adamantane-oxalamide derivatives, N,N′-bis(1-adamantylglycine methyl ester)oxalamide (meso-1 and rac-1), N,N′-bis(3-aminoadamantane-1-carboxylic acid methyl ester)oxalamide (2) and N,N′-bis(3-aminoadamantane-1-carboxylic acid)oxalamide (3) were prepared and structurally characterized by spectroscopic methods and X-ray analysis. Crystal packing of the structures meso-1 and rac-1 is defined by one-dimensional α-networks of hydrogen-bonded chains. The crystal structures of 2 and 3 are characterized by two-dimensional β-networks of hydrogen bonds. The oxalamide 3 crystallizes as the solvates only. In the crystal structure of 3 the protic solvent participates in hydrogen bonding with the oxalamide moieties. However, in non-protic solvents 3 crystallizes as a solvate but the solvent does not participate in hydrogen bonding. The two-dimensional network of hydrogen bonds connecting molecules of 3 generates channels, which are filled by discrete solvent molecules.