Identifying ferroresonance initiation for a range of initial conditions and parameters

The paper presents an experimental and numerical investigation carried out on a ferroresonant circuit in order to determine to what extent the initiation of ferroresonance depends on initial conditions and phase shift. The range of voltage source values at which the initiation of ferroresonance depends on initial conditions and phase shift is named as a possible ferroresonant range, and is determined numerically and experimentally.     

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.     

Macroscopic Time Evolution and MaxEnt Inference for Closed Systems with Hamiltonian Dynamics

MaxEnt inference algorithm and information theory are relevant for the time evolution of macroscopic systems considered as problem of incomplete information. Two different MaxEnt approaches are introduced in this work, both applied to prediction of time evolution for closed Hamiltonian systems. The first one is based on Liouville equation for the conditional probability distribution, introduced as a strict microscopic constraint on time evolution in phase space. The conditional probability distribution is defined for the set of microstates associated with the set of phase space paths determined by solutions of Hamilton’s equations. The MaxEnt inference algorithm with Shannon’s concept of the conditional information entropy is then applied to prediction, consistently with this strict microscopic constraint on time evolution in phase space. The second approach is based on the same concepts, with a difference that Liouville equation for the conditional probability distribution is introduced as a macroscopic constraint given by a phase space average. We consider the incomplete nature of our information about microscopic dynamics in a rational way that is consistent with Jaynes’ formulation of predictive statistical mechanics, and the concept of macroscopic reproducibility for time dependent processes. Maximization of the conditional information entropy subject to this macroscopic constraint leads to a loss of correlation between the initial phase space paths and final microstates. Information entropy is the theoretic upper bound on the conditional information entropy, with the upper bound attained only in case of the complete loss of correlation. In this alternative approach to prediction of macroscopic time evolution, maximization of the conditional information entropy is equivalent to the loss of statistical correlation, and leads to corresponding loss of information. In accordance with the original idea of Jaynes, irreversibility appears as a consequence of gradual loss of information about possible microstates of the system.     

On the anomalous large-scale flows in the Universe

Recent combined analyses of the CMB and galaxy cluster data reveal unexpectedly large and anisotropic peculiar velocity fields at large scales. We study cosmic models with included vorticity, acceleration and total angular momentum of the Universe in order to understand the phenomenon. The Zel’dovich model is used to mimic the low redshift evolution of the angular momentum. Solving coupled evolution equations of the second order for density contrast in corrected Ellis–Bruni covariant and gauge-invariant formalism one can properly normalize and evaluate integrated Sachs–Wolfe effect and peculiar velocity field. The theoretical results compared to the observations favor a much larger matter content of the Universe than that of the concordance model. Large-scale flows appear anisotropic with dominant components placed in the plane perpendicular to the axis of vorticity (rotation). The integrated Sachs–Wolfe term has a negative contribution to the CMB fluctuations for the negative cosmological constant and it can explain the observed small power of the CMB TT spectrum at large scales. The rate of the expansion of the Universe may be substantially affected by the angular momentum if its magnitude is large enough.     

Container Systems II: An Experimental Study of the High‐Pressure Intramolecular Cycloaddition of Tethered Furans and Anthracenes onto Norbornane Cyclobutene‐1,2‐diesters

A new class of container molecules is described and the first steps in producing protypes are reported. Central to the approach is the formation of polynorbornanes with cyclobutene‐1,2‐difurfuryl esters at the terminus or similar functionality at the bridgehead of a central norbornane subunit. The synthesis of the furfuryl starting materials is described as well as their anthracenyl counterparts. Conversion to the container systems involved the intermolecular linking of the furfuryl or anthracene by treatment with dimethyl acetylene dicarboxylate (DMAD) in a Diels–Alder (DA) protocol under thermal or high‐pressure (HP) conditions. In practice, no intermolecular linking occurred between the norbornane substrates and only products from DA 1:1‐addition with DMAD were produced. Intramolecular addition of one of the furfuryl units onto the cyclobutene π‐bond was detected under HP conditions, and this intermolecular product was capable of isolation and characterization by working at room temperature or below, but reverted to starting material above room temperature. When conducted in the presence of DMAD, a single 1:1‐adduct was obtained in which one furfuryl moiety was intramolecularly cyclized and the other present as the DMAD adduct; again this product underwent retro‐DA reaction at 40°C. Similar intermolecular cyclization was observed with the bis‐anthracenyl esters. The stereoselectivity of the intermolecular attack of the furfuryl diene with the dienophilic cyclobutene gave a single adduct by endo‐face attack in which the oxa‐bridge is endo‐positioned. Quantum chemical DFT calculations (B3LYP) predict that the formation of the endo‐isomer is kinetically favored and that relief of ring strain enhances the rate of retro‐Diels–Alder in the tethered system.     

Base-catalyzed reactions of environmentally relevant N-chloro-piperidines. A quantum-chemical study

Electronic structure methods have been applied to calculate the gas and aqueous phase reaction energies for base-induced rearrangements of N-chloropiperidine, N-chloro-3-(hydroxymethyl)piperidine, and N-chloro-4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine. These derivatives have been selected as representative models for studying the chemical fate of environmentally relevant chloramines. The performance of different computational methods (MP2, MP4, QCISD, B3LYP and B2PLYP) for calculating the thermochemistry of rearrangement reactions was assessed. The latter method produces energies similar to those obtained at G3B3(+) level, which themselves have been tested against experimental results. Experimental energy barriers and enthalpies for ring inversion, nitrogen inversion and dehydrochlorination reactions in N-chloropiperidine have been accurately reproduced when solvent effects have been included. It was also found that the combined use of continuum solvation models (e.g. CPCM) and explicit consideration of a single water molecule is sufficient to properly describe the water-assisted rearrangement of N-chlorinated compounds in basic media. In the case of N-chloro-4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine, which represents the chlorinated metabolite of the antidepressant paroxetine, several different reactions (intramolecular addition, substitution, and elimination reactions) have been investigated. Transition state structures for these processes have been located together with minimum energy structures of conceivable products. Imine 4A is predicted to be the most stable reaction product, closely followed by imine 4B and oxazinane 8, while formation of isoxazolidine 7 is much less favourable. Calculated reaction barriers in aqueous solution are quite similar for all four processes, the lowest barrier being predicted for the formation of imine 4A.     

Domino Diels-Alder reactions of N-methoxyethyl-7-oxa-norbornadiene-2,3-dicarboximide: an elusive, highly reactive dienophile

Flash vacuum pyrolysis (FVP) has been used to generate the novel 7-oxa-norbornadiene-2,3-dicarboxylic imide that in situ gave an unprecedented cycloaddition reaction cascade with the imidofuran, a side-product of FVP. Stereoselectivity of cycloadditions was studied with the aid of density functional calculations, which fully support observed exo/endo-selectivity.     

Poly(D,L-lactide-co-glycolide)/hydroxyapatite core-shell nanospheres. Part 1: A multifunctional system for controlled drug delivery

Biodegradable poly(d,l-lactide-co-glycolide) (PLGA) and bioactive hydroxyapatite (HAp) are selected for the formation of a multifunctional system with the specific core-shell structure to be applied as a carrier of a drug. As a result, both components of PLGA/HAp core-shells are able to capture one part of the drug. Polymeric shells consisting of small nanospheres up to 20nm in size act as a matrix in which one part of the drug is dispersed. In the same time, ceramic cores are formed of rod-like hydroxyapatite particles at the surface of which another part of the drug is adsorbed onto the interface between the polymer and the ceramics. The content of the loaded drug, as well as the selected solvent/non-solvent system, have a crucial influence on the resulting PLGA/HAp morphology and, finally, unimodal distribution of core-shells is obtained. The redistribution of the drug between the organic and inorganic parts of the material is expected to provide an interesting contribution to the kinetics of the drug release resulting in non-typical two-step drug release.     

Modeling long-range cross-correlations in two-component ARFIMA and FIARCH processes

We investigate how simultaneously recorded long-range power-law correlated multivariate signals cross-correlate. To this end we introduce a two-component ARFIMA stochastic process and a two-component FIARCH process to generate coupled fractal signals with long-range power-law correlations which are at the same time long-range cross-correlated. We study how the degree of cross-correlations between these signals depends on the scaling exponents characterizing the fractal correlations in each signal and on the coupling between the signals. Our findings have relevance when studying parallel outputs of multiple component of physical, physiological and social systems.     

Electron-Rich EDOT Linkers in Tetracationic bis-Triarylborane Chromophores: Influence on Water Stability,Biomacromolecule Sensing,and Photoinduced Cytotoxicity

Three novel tetracationic bis-triarylboranes with 3,4-ethylenedioxythiophene (EDOT) linkers, and their neutral precursors, showed significant red-shifted absorption and emission compared to their thiophene-containing analogues, with one of the EDOT-derivatives emitting in the NIR region. Only the EDOT-linked trixylylborane tetracation was stable in aqueous solution, indicating that direct attachment of a thiophene or even 3-methylthiophene to the boron atom is insufficient to provide hydrolytic stability in aqueous solution. Further comparative analysis of the EDOT-linked trixylylborane tetracation and its bis-thiophene analogue revealed efficient photo-induced singlet oxygen production, with the consequent biological implications. Thus, both analogues bind strongly to ds-DNA and BSA, very efficiently enter living human cells, accumulate in several different cytoplasmic organelles with no toxic effect but, under intense visible light irradiation, they exhibit almost instantaneous and very strong cytotoxic effects, presumably attributed to singlet oxygen production. Thus, both compounds are intriguing theranostic agents, whose intracellular and probably intra-tissue location can be monitored by strong fluorescence, allowing switching on of the strong bioactivity by well-focused visible light.