gem-Difluorosubstituted NH-azomethine ylides in the synthesis of 4-fluorooxazolines via the three-component reaction of imines, trifluoroacetophenones and CF2Br2

A simple one-step synthesis of a new class of fluorinated heterocycles, 4-fluoro-3-oxazolines, from diarylmethanimines, trifluoroacetophenones and CF₂Br₂ is described. The reaction proceeds via the sequential formation of difluorocarbene and a gem-difluorosubstituted NH-azomethine ylide, followed by 1,3-dipolar cycloaddition with a ketone.     

Rearrangement of 2-azanorbornenes to tetrahydrocyclopenta[c]pyridines under the action of activated alkynes – A short pathway for construction of the altemicidin core

A simple approach to a series of 2,4a,7,7a-tetrahydro-1H-cyclopenta[c]pyridines was proposed on the basis of the amino-Claisen rearrangement of readily accessible 2-azabicyclo[2.2.1]hept-5-enes under the action of dialkyl acetylenedicarboxylates, methyl propiolate or propiolamide. The rearrangement is highly diastereoselective and leads to the formation of only one isomer with cis-annulation of the five- and six-membered rings in satisfactory yields. Using the developed method, close analogs of the altemicidin and SB-203207 cores were synthesized.     

Total Reflection X-Ray Fluorescence Determination of Rare Earth Elements in Mineral Water Using a Combined Preconcentration Technique

A combined approach for the simultaneous determination of lanthanum, cerium, praseodymium, neodymium, and samarium in mineral water in the range from?·?10^?2 to 10¹?µg/L by total reflection X-ray fluorescence analysis is reported. The combined technique of preconcentration of the rare earth elements ions includes the codeposition of their hydroxides on a collector and dispersive liquid–liquid microextraction by chloroform to form complexes with 1-(2-pyridylazo)-2-naphthol. The results for the determination of lanthanum and light lanthanides in natural water samples with the combined approach are in good agreement with measurements obtained by inductively coupled plasma–mass spectrometry.     

Interplay between solid state microstructure and photophysics for poly(9,9‐dioctylfluorene) within oriented polyethylene hosts

We present a study of isotropic and uniaxially oriented binary blend films comprising ≤1 wt % of the conjugated polymer poly(9,9‐dioctylfluorene) (PFO) dispersed in both ultra‐high molecular weight (UHMW) and linear‐low‐density (LLD) polyethylene (PE). Polarized absorption, fluorescence and Raman spectroscopy, scanning electron microscopy, and X‐ray diffraction are used to characterize the samples before and after tensile deformation. Results show that blend films can be prepared with PFO chains adopting a combination of several distinct molecular conformations, namely glassy, crystalline, and the so‐called β‐phase, which directly influences the resulting optical properties. Both PFO concentration and drawing temperature strongly affect the alignment of PFO chains during the tensile drawing of the blend films. In both PE hosts, crystallization of PFO takes place during drawing; the resulting ordered chains show optimal optical anisotropy. Our results clarify the PFO microstructure in oriented blends with PE and the processing conditions required for achieving the maximal optical anisotropy. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 22–38     

Validation of large eddy simulation method for study of flatness and skewness of decaying compressible magnetohydrodynamic turbulence

In the present work we study potential applicability of large eddy simulation (LES) method for prediction of flatness and skewness of compressible magnetohydrodynamic (MHD) turbulence. The knowledge of these quantities characterizes non-Gaussian properties of turbulence and can be used for verification of hypothesis on Gaussianity for the turbulent flow under consideration. Prediction accuracy of these quantities by means of LES method directly determines efficiency of reconstruction of probability density function (PDF) that depends on used subgrid-scale (SGS) parameterizations. Applicability of LES approach for studying of PDF properties of turbulent compressible magnetic fluid flow is investigated and potential feasibilities of five SGS parameterizations by means of comparison with direct numerical simulation results are explored. The skewness and the flatness of the velocity and the magnetic field components under various hydrodynamic Reynolds numbers, sonic Mach numbers, and magnetic Reynolds numbers are studied. It is shown that various SGS closures demonstrate the best results depending on change of similarity numbers of turbulent MHD flow. The case without any subgrid modeling yields sufficiently good results as well. This indicates that the energy pile-up at the small scales that is characteristic for the model without any subgrid closure, does not significantly influence on determination of PDF. It is shown that, among the subgrid models, the best results for studying of the flatness and the skewness of velocity and magnetic field components are demonstrated by the Smagorinsky model for MHD turbulence and the model based on cross-helicity for MHD case. It is visible from the numerical results that the influence of a choice subgrid parametrization for the flatness and the skewness of velocity is more essential than for the same characteristics of magnetic field.     

Intracellular Breakable and Ultrasound‐Responsive Hybrid Microsized Containers for Selective Drug Release into Cancerous Cells

This work reports an efficient and straightforward strategy to fabricate hybrid microsized containers with reduction‐sensitive and ultrasound‐responsive properties. The ultrasound and reductive sensitivity are visualized using scanning electron microscopy, with the results showing structural decomposition upon ultrasound irradiation and in the presence of reducing agent. The ultrasound‐responsive functionalities of hybrid carriers can be used as external trigger for rapid controlled release, while prolonged drug release can be achieved in the presence of reducing agent. To evaluate the potential for targeted drug delivery, hybrid microsized containers are loaded with the anticancer drug doxorubicin (Dox). Such hybrid capsules can undergo structural intracellular degradation after cellular uptake by human cervical cancer cell line (HeLa), resulting in Dox release into cancer cells. In contrast, there is no Dox release when hybrid capsules are incubated with human mesenchymal stem cells (MSCs) as an example of normal human cells. The cell viability results indicate that Dox‐loaded capsules effectively killed HeLa cells, while they have lower cytotoxicity against MSCs as an example of healthy cells. Thus, the newly developed intracellular‐ and ultrasound‐responsive microcarriers obtained via sol‐gel method and layer‐by‐layer technique provide a high therapeutic efficacy for cancer, while minimizing adverse side effect.     

Ionomer-surfactant self-assembly in low-polarity solvents

A systematic study of complexation reactions of sulfonated polystyrene ionomers containing up to 5 molar percent of polar chain units with various oil-soluble surfactants is carried out in low-polarity organic solvents. Dipole-dipole attractions of the components lead to the formation of complexes characterized by limiting compositions and an unusual polymer-colloidal morphology of joint clusters and/or micelles. The limiting compositions (φ) for the complexes formed between ionomers and surfactant of the same charge (bis(2-ethylhexyl)sulfosuccinate sodium salt), or nonionic surfactants (primarily aliphatic amines) are equal to 15–30 surfactant molecules per one ionomer salt/acid group on average, with φ depending on the hydrophilic-lypophilic balance of the components, the initial aggregation state of surfactant and the nature of low-polarity solvent. Ionomersurfactant complexation is accompanied by disruption of self-contacts of ionomer salt/acid groups, leading to “unfastening” and expansion of the ionomer coils in dilute solution. The “driving force” of the ionomersurfactant complexation and the structure of the resultant complexes are discussed.     

Intersecting loop models on : rigorous results

We consider a general class of (intersecting) loop models in d dimensions, including those related to high-temperature expansions of well-known spin models. We find that the loop models exhibit some interesting features – often in the “unphysical” region of parameter space where all connection with the original spin Hamiltonian is apparently lost. For a particular n=2, d=2 model, we establish the existence of a phase transition, possibly associated with divergent loops. However, for n1 and arbitrary d there is no phase transition marked by the appearance of large loops. Furthermore, at least for d=2 (and n large) we find a phase transition characterised by broken translational symmetry.