Computational study of radicals derived from hydroxyurea and its methylated analogues

Structural and electronic properties and chemical fate of free radicals generated from hydroxyurea (HU) and its methylated analogues N-methylhydroxyurea (NMHU) and O-methylhydroxyurea (OMHU) are of utmost importance for their biological and pharmacological effects. In this work the cis/trans conformational processes, tautomerizations, and intramolecular hydrogen and methyl migrations in hydroxyurea-derived radicals have been considered. Potential energy profiles for these reactions have been calculated using two DFT functionals (BP86 and B3LYP) and two composite models (G3(MP2)RAD and G3B3). Solvation effects have been included both implicitly (CPCM) and explicitly. It has been shown that calculated energy barriers for free radical rearrangements are significantly reduced when a single water molecule is included in calculations. In the case of HU-derived open-shell species, a number of oxygen-, nitrogen-, and carbon-centered radicals have been located, but only the O-centered radicals (e1 and z1) fit to experimental isomeric hyperfine coupling constants (hfccs) from EPR spectra. The reduction of NMHU and OMHU produces O-centered and N-centered radicals, respectively, with the former being more stable by ca. 60 kJ mol(-1). The NMHU-derived radical e4 undergoes rearrangements, which can result in formation of several conceivable products. The calculated hfccs have been successfully used to interpret the experimental EPR spectra of the most probable rearranged product 10. Reduction potentials of hydroxyureas, radical stabilization energy (RSE) and bond disocciation energy (BDE) values have been calculated to compare stabilities and reactivities of different subclasses of free radicals. It has been concluded, in agreement with experiment, that reductions of biologically relevant tyrosyl radicals by HU and NMHU are thermochemically favorable processes, and that the order of reactivity of hydroxyureas follows the experimentally observed trend NMHU > HU > OMHU.     

Role of complement anaphylatoxin C3a in photodynamic therapy-elicited engagement of host neutrophils and other immune cells

Tumor treatment by photodynamic therapy (PDT) provokes a host-protective inflammatory and acute-phase response and an immune reaction. Neutrophilia manifested in this context is driven by multiple mediators of neutrophil chemotaxis orchestrated by an activated complement system. Mouse FsaR fibrosarcoma was used in this study to further investigate neutrophilia induced by Photofrin-based PDT. The complement anaphylatoxin C3a was identified as a major chemoattractant in the advanced phase of PDT-induced neutrophilia, because injecting mice with antibodies blocking its receptor C3aR significantly inhibited the increase in neutrophil levels 8 h after PDT. At the same time point, an increased C3aR expression was detected in neutrophils, monocytes and B lymphocytes in the blood of host mice. Peritoneal macrophages and mast cells harvested from treatment-naive mice exhibited elevated C3aR expression after coincubation in vitro for 8 h with PDT-treated FsaR cells. Thus, C3a emerges as one of the key effector molecules engaged in PDT-induced host response.     

Conditions of matrices in discrete tension spline approximations of DMBVP

Some splines can be defined as solutions of differential multi-point boundary value problems (DMBVP). In the numerical treatment of DMBVP, the differential operator is discretized by finite differences. We consider one dimensional discrete hyperbolic tension spline introduced in (Costantini et al. in Adv Comput Math 11:331–354, 1999), and the associated specially structured pentadiagonal linear system. Error in direct methods for the solution of this linear system depends on condition numbers of corresponding matrices. If the chosen mesh is uniform, the system matrix is symmetric and positive definite, and it is easy to compute both, lower and upper bound, for its condition. In the more interesting non-uniform case, matrix is not symmetric, but in some circumstances we can nevertheless find an upper bound on its condition number. This research was supported by Grant 0037114, by the Ministry of Science, Education and Sports of the Republic of Croatia.     

Adsorption of SO2 from Wet Mixtures on Hydrophobic Zeolites

Breakthrough curve measurements of SO₂ and water vapor were carried out on a number of selected mordenite and pentasil zeolites from their binary and ternary mixtures with CO₂ at 50 and 100°C. SO₂ capacities of these samples were found to be significantly reduced by the presence of water. Competitive adsorption led to unusually high overshoot peaks of SO₂ breakthrough curves. On the other hand, SO₂ was found to displace water on the samples with very high silica to alumina ratio. A linear driving force, isothermal model was used to predict the breakthrough curves. Langmuir and extended Langmuir equilibrium models were used to describe the equilibrium properties of water and SO₂, respectively. The overall mass transfer resistance obtained from the model was compared to the values calculated from a simplified biporous adsorbent model to shed some light on the adsorption kinetics.     

Numerical Simulation of Air Flow in Model Room

Efficient, and appropriate indoor air environment is important issue in building design. Air flow patterns which are formed in the room are mainly depended on its geometrical parameters. Investigation of flow patterns are performed on a relatively simple geometry of model room, with a small obstacle (partition) in it. There are several interesting flow phenomena which are present in the model room: flow through sudden geometry expansion, stagnation flow with lateral boundaries, flow over the obstacle, etc. Since the air velocities are low, it is assumed that flow is incompressible. Numerical calculations of these patterns have been done using RANS modeling approach. For all calculations an extended version of open-source CFD software OpenFOAM was used. Several turbulence models have been used for RANS approach, with special attention on their performance in capturing unsteady flow phenomena. Comparison of obtained numerical results and available experimental results for mean velocities shown good agreement. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Water vapor adsorption equilibria and mass transport in unmodified and modified cellulose fiber-based materials

Water vapor adsorption isotherms of different unmodified and coated paper samples were studied to determine their suitability as water barrier packaging materials. The sorption behavior of these samples was compared with commercially available paper. The experimental data were analyzed using the Hailwood–Horrobin (H–H), Guggenheim–Anderson–De Boer (GAB) and BET models for extraction of isotherm parameters and determination of monolayer moisture contents. The H–H and GAB models were found to provide good fits to the experimental data. The monolayer moisture content of modified papers was less than 3.0 % (dry basis) as compared to unmodified paper samples (4.20 %), at saturation. It was also observed that the sorption behavior of modified paper samples differed with substrate type. Water vapor permeability (WVP) of unmodified and coated paper samples at the temperatures of 25 and 38 °C were also measured for a wide range of vapor partial pressure gradients. The permeabilities of the modified samples were found to be generally low compared to the unmodified (reference) paper sample. Among the investigated samples, PLA and PHBV coated paper samples showed higher mass transfer resistance to water vapor transport. Furthermore, the water vapor permeabilities of different samples were found to be relatively constant up to the modest relative humidity levels; however, at the higher humidity levels they showed increasing trend with the further increase in relative humidity. Results of this study confirmed that blocking of active surface sites by coating with PLA and PHBV is the most effective way to increase the water vapor barrier properties of modified papers, thus making them the appropriate candidates for green-based food packaging materials.     

The topology at infinity of Out(Fn)

We construct a bordification of Outer Space analogous to the Borel-Serre bordification of symmetric spaces. As an application, we show that Out(F _n ) is (2n-5)-connected at infinity and that it is a virtual duality group of dimension 2n-3. Oblatum 4-III-1998 & 2-XII-1999?Published online: 21 February 2000     

Numerically stable algorithm for cycloidal splines

We propose a knot insertion algorithm for splines that are piecewisely in L{1, x, sin x, cos x}. Since an ECC-system on [0, 2π] in this case does not exist, we construct a CCC-system by choosing the appropriate measures in the canonical representation. In this way, a B-basis can be constructed in much the same way as for weighted and tension splines. Thus we develop a corner cutting algorithm for lower order cycloidal curves , though a straightforward generalization to higher order curves, where ECC-systems exist, is more complex. The important feature of the algorithm is high numerical stability and simple implementation. This research was supported by Grant 037-1193086-2771, by the Ministry of science, higher education and sports of the Republic of Croatia.     

Antimony(III) chloride-catalysed Biginelli reaction: a versatile method for the synthesis of dihydropyrimidinones through a different reaction mechanism

Antimony(III) chloride (20 mol %) in refluxing acetonitrile efficiently catalyses the synthesis of dihydropyrimidinones (50-90% yields) by the Biginelli reaction of aromatic aldehydes, acetoacetate esters and urea. This reaction proceeds through 3-ureido-crotonates followed by cyclisation with an aromatic aldehyde to the dihydropyrimidinone.     

The associated variety of an induced representation

This paper studies the behavior of the associated variety under induction from real parabolic subgroups. We derive a formula for the associated variety of an induced module which is analogous to the formula for the wave front set of a derived functor module obtained by Barbasch and Vogan.