Stability of Highly Concentrated Water-in-Oil Emulsions with Magnetic Nanoparticles and the Structure of Highly Porous Polymers Formed on Their Basis

Colloid Journal - The influence of the concentration and size of magnetite nanoparticles on the stability of highly concentrated water-in-oil emulsions containing styrene–divinylbenzene...     

Highly porous polymeric sponges for oil sorption

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The Stability of Highly Concentrated Water-in-Oil Emulsions and Structure of Highly Porous Polystyrene Produced from Them

The porosity of polymer materials produced by polymerizing dispersion media of highly concentrated emulsions may be predicted, provided that the emulsions are stable. The study of the stability of water-in-oil (W/O) emulsions containing styrene as a dispersion medium at 25 and 65°C has shown that emulsions with a dispersed phase fraction of 0.75 and sorbitan monooleate concentrations of 1.5–20.0 vol % are stable to coalescence but are unstable to sedimentation. Emulsions with a dispersed phase fraction of 0.95 are stable to both coalescence and sedimentation at sorbitan monooleate concentrations of 10–20 vol %. Open-pore polymer materials are formed from emulsions with dispersed phase fractions of 0.75 and 0.95 at sorbitan monooleate concentrations of 2.0–3.5 and 10–12 vol %, respectively. At a dispersed phase fraction of 0.75 and a sorbitan monooleate concentration of <2 vol %, a multiple O/W/O emulsion is formed, the polymerization of which yields a porous polymer material containing spherical polystyrene particles inside pores. At higher surfactant concentrations in emulsions with dispersed phase fractions of 0.75 and 0.95 partly destroyed porous materials are formed.     

A network-based data mining approach to portfolio selection via weighted clique relaxations

We introduce a new network-based data mining approach to selecting diversified portfolios by modeling the stock market as a network and utilizing combinatorial optimization techniques to find maximum-weight s-plexes in the obtained networks. The considered approach is based on the weighted market graph model, which is used for identifying clusters of stocks according to a correlation-based criterion. The proposed techniques provide a new framework for selecting profitable diversified portfolios, which is verified by computational experiments on historical data over the past decade. In addition, the proposed approach can be used as a complementary tool for narrowing down a set of “candidate” stocks for a diversified portfolio, which can potentially be analyzed using other known portfolio selection techniques.     

Computational study of the US stock market evolution: a rank correlation-based network model

This paper presents a computational study of global characteristics of the US stock market using a network-based model referred to as the market graph. The market graph reflects similarity patterns between stock return fluctuations via linking pairs of stocks that exhibit “coordinated” behavior over a specified period of time. We utilized Spearman rank correlation as a measure of similarity between stocks and considered the evolution of the market graph over the recent decade between 2001–2011. The observed market graph characteristics reveal interesting trends in the stock market over time, as well as allow one to use this model to identify cohesive clusters of stocks in the market.     

Ferrite-induced breakdown. Mechanism of induction by thermal surface explosion

The conditions are investigated for gas breakdown above an Ni–Zn (M4OONN) ferrite surface. The assumption that the discharge is initiated by a thermal explosion of a surface layer of the ferrite modified by current flowing through it is verified experimentally and theoretically. The electric and thermophysical properties of the (ferrite+annealed layer) system are determined. The experimentally observed temporal characteristics of the prebreakdown phase of the discharge and the dependences of the breakdown voltage on the discharge-circuit parameters are described within the framework of a single model.Translated from FIAN Preprint No. 120, Lebedev Physics Institute, Moscow, 1990.     

Mathematical modeling of styrene and butyl acrylate homopolymerization via the reversible addition-fragmentation mechanism

A mathematical model is suggested for the kinetics of the controlled free-radical polymerization of two monomers—styrene and butyl acrylate—via the reversible addition-fragmentation chain transfer (RAFT) mechanism (with 2,2′-azobisisobutyronitrile as the initiator and dibenzyl trithiocarbonate as the RAFT agent). A comparison of experimental molecular weight characteristics of polystyrene and poly(butyl acrylate) with those calculated using the model indicates that the model is valid. The effects of the process control parameters (temperature and the initial concentrations of the initiator, monomer, and RAFT agent) have been elucidated by a computational experiment.     

Spatio-temporal dynamics of electron density in femtosecond laser microplasma of gases

The formation and evolution of femtosecond laser plasma produced in microvolumes of gases at different pressures upon their multiply ionization by high intensity pulses of fundamental and second harmonics of a Ti:sapphire laser is studied. The interferometric technique for precise ultrafast optical diagnostics of such plasma was applied. The numerical technique of interferogram processing and reconstruction of instant spatial distribution of refractive index and free electron density in laser-induced plasma applied for this proposes is described. The spatiotemporal distribution of the refractive index and free electron density were studied with a spatial resolution of ～1 μ m and a temporal resolution of ～70 fs.     

Optically pumped molecular-iodine laser on the 342-nm band

Lasing of molecular iodine has been observed on 342-nm band system. The laser was produced with optical pumping by the radiation of high-current discharge mixtures of iodine vapour, sulfur hexafluoride and argon. The highest energy output 0.4 J in a 5 μs pulse corresponding to the specific laser energy of ～10^-3 J/cm³ has been obtained.